佐々木 克彦(ササキ カツヒコ) |

工学研究院 機械・宇宙航空工学部門 機械材料システム |

教授 |

Last Updated :2023/11/02

- 連成解析 粘弾塑性変形 熱応力 構造解析 ステント 塑性構成式 電子基板実装 Structural Analysis Lead Free Solder Alloy Electronic Packaging

- 2007年 - 2009年 同准教授（工学研究科人間機械システムデザイン専攻） 准教授
- 2009年 - 北海道大学大学院 教授
- 2009年 - Professor
- 2006年 北海道大学助教授（工学研究科人間機械システムデザイン専攻） 助教授
- 2006年 - Associate Professor,Division of Human Mechanical Systems and Design

- Optimization of CFRP skeletal structure of morphing wings and manufacturing by electrodeposition ...Kazuaki Katagiri, Choong Sik Park, Sonomi Kawakita, Masato Tamayama, Shhinya Honda, Katsuhiko SasakiAIAA SCITECH 2023 Forum, 2023 1708 2023年01月23日 [査読有り]
- Kazuaki Katagiri, Daekwi Kim, Choong Sik Park, Sonomi Kawakita, Masato Tamayama, Koki Kayano, Shinya Honda, Katsuhiko Sasaki, Makoto YamazakiPROCEEDINGS OF THE 2021 ASIA-PACIFIC INTERNATIONAL SYMPOSIUM ON AEROSPACE TECHNOLOGY (APISAT 2021), VOL 1 912 879 - 891 2023年To achieve efficient flight by minimizing energy consumption, a morphing wing that allows large and smooth deformation similar to a wing of a migratory bird is required. Previously, the authors have developed a migratory-sized unmanned aerial vehicle (UAV) with a twist morphing wing. The twist morphing wing was manufactured using a carbon fiber reinforced plastics (CFRP) with applying the electrodeposition resin molding (ERM) method, which was developed by authors. In the ERM method, resin impregnation proceeds in a liquid by electrophoresis. Thus, manufacturing process is very efficient because neither pressurization nor evacuation are necessary. On the other hand, although the molding of the twist morphing wing is efficient, an optimal design is important for the twist morphing wing to lower the torsional rigidity to reduce the driving force of the morphing and increase the bending rigidity to support aerodynamic loads. Therefore, in this study, the spar of the twist morphing wing was designed to be arranged in a triangle. Furthermore, the twist morphing wing structures were fabricated by the ERM method, and by a 3D printer for benchmarking. So, torsion and bending deformation properties of the twist morphing wing were confirmed under the aerodynamic loading condition, and validated by finite element analysis. As a result, it was confirmed that the manufacturing efficiency of the ERM method was superior to that of the 3D printer. Additionally, the torsional rigidity of the twisted morphing wing was almost the same, regardless of the manufacturing method. Furthermore, the bending rigidity of the specimen manufactured by the ERM method was higher than that of the 3D printer.
- Ken-ichi Ohguchi, Katsuhiko Sasaki, Kohei Fukuchi, Yorimasa Tsubota, Takuro Mita, Wataru Nagai, Kouji Ohsato, Nobuaki ShinyaMechanics of Time-Dependent Materials 2022年11月11日
- Shinya Honda, Hiraku Takisawa, Ryo Takeda, Katsuhiko Sasaki, Kazuaki KatagiriMechanics of Advanced Materials and Structures 2022年07月12日 [査読有り]

The effect of both curvilinear fiber orientation and thickness distribution on modal damping of carbon fiber reinforced plastics (CFRP) fabricated by electrodeposition resin molding (ERM) was investigated. Tailored fiber placement (TFP) was used to manufacture carbon fiber (CF) performs with continuous curvilinear fiber paths or variable-axial properties. The damping of composites was calculated using the concept of specific damping capacity (SDC). Fiber shapes was optimized to maximize the first modal SDC using particle swarm optimization (PSO). As a result, the optimum fiber shape improves both the first natural frequency and modal SDC in comparison with several unidirectional fiber shapes. - Kazuaki Katagiri, Naoko Kishimoto, Haruna Yamaguchi, Toshihiko Okumura, Sonomi Kawakita, Shinya Honda, Katsuhiko SasakiMECHANICS OF ADVANCED MATERIALS AND STRUCTURES 2022年06月Cellulose nanofibers (CNFs) are sustainable materials with high specific strengths. To enhance the impact properties of carbon fiber reinforced plastics (CFRPs), the authors have developed an efficient process for incorporating a non-hydrophobized CNF dispersion layer into CFRPs. In this study, the impact properties of CFRP with asymmetrically stacked CNF dispersion layer was investigated by conducting the instrumented Charpy impact tests. Two types of CNFs were used for comparison. Consequently, by inserting the CNF dispersion layer into the opposite side of the striking surface, the Charpy impact value increased by 26% compared to CFRP without CNF dispersion layer.
- Kazuaki Katagiri, Choong Sik Park, Sonomi Kawakita, Daekwi Kim, Masato Tamayama, Shinya Honda, Katsuhiko Sasaki, Makoto YamazakiAIAA SCITECH 2022 Forum 2022年01月03日
- 才脇 武, 本田 真也, 片桐 一彰, 佐々木 克彦, 武田 量Dynamics & Design Conference 2022 145 一般社団法人 日本機械学会 2022年Tailored Fiber Placement (TFP) is an embroidery technique that enables it possible to design free fiber shapes on base material sheets. The TFP generally creates curved fibers on a flat surface. However, CFRP structures are often used as shell structures rather than as flat plates, and there is not enough research to design fiber shapes on curved surfaces. In this research, we applied our previous optimization method for curved fiber shapes to shell structures. Curved fiber shapes were created by the linear combination of radial basis functions (RBFs) to represent complex fiber shapes. The fiber shape on a curved surface was represented by projecting the fiber shape on a plane surface using a coordinate transformation technique. Using this method, we investigated optimum fiber shapes to improve the first natural frequency of shell structure composites. The results showed that the optimum fiber shape gave higher natural frequencies than the linear fiber orientation. Obtained optimum fiber shape resulted in higher natural frequencies than the linear fiber orientation.
- 本田 真也, 瀧澤 拓, 片桐 一彰, 佐々木 克彦, 武田 量理論応用力学講演会 講演論文集 66 163 日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」 2022年本研究では電着樹脂含浸法により作製される炭素繊維強化複合材 (CFRP; Carbon Fiber Reinforced Plastics)の減衰特性の推定及び向上を目的とした繊維形状の最適化を行った．減衰を固有減衰容量 (SDC) によってモデル化し，減衰の数値計算に必要となる材料の減衰パラメータについては，実験モード解析と有限要素解析を併用して逆解析的に同定した．最適化では，第1次モードSDCを最大化する曲線状の繊維形状を探索した．また，曲線状の繊維形状で生じる板厚分布を推定し，有限要素解析に適用した．最適化で得られた繊維形状を適用した場合，いくつかの直線配向と比べて第1次固有振動数及びモードSDCが向上したため，曲線状の繊維配向は減衰の向上に有効であることがわかった．
- 本田 真也, 瀧澤 拓, 片桐 一彰, 佐々木 克彦, 武田 量最適化シンポジウム講演論文集 2022.14 U00010 一般社団法人 日本機械学会 2022年Fiber shape optimization was performed to improve the damping properties of CFRP fabricated by electrodeposition resin molding (EDRM) method. Damping properties of composites were modeled by the specific damping capacity (SDC), and the material damping parameters required for numerical estimation were identified by an inverse analysis using results of experimental modal analysis and finite element analysis. In the optimization, a curvilinear fiber shape that maximizes the first mode SDC was explored. The thickness distribution due to the curvilinear fiber shape was estimated and applied to the finite element analysis. The fiber shapes obtained by the optimization improved the first natural frequencies and mode SDCs compared to several straight fiber orientations, indicating that the curved fiber orientation is effective in improving damping.
- Kazuaki Katagiri, Naoko Kishimoto, Haruna Yamaguchi, Toshihiko Okumura, Sonomi Kawakita, Shinya Honda, Katsuhiko SasakiMechanics of Advanced Materials and Structures 1 - 10 2021年12月30日
- Ryo Takeda, Fumiya Sato, Hiroichi Yokoyama, Katsuhiko Sasaki, Nobuyuki Oshima, Akiyoshi Kuroda, Hideyoshi Takashima, Chenyu Li, Shinya Honda, Hiroyuki KamiyaAnnals of Vascular Surgery 2021年10月
- KAZUAKI KATAGIRI, CHOONG SIK PARK, SHIMPEI YAMAGUCHI, SONOMI KAWAKITA, KIM DAEKWI, SHINYA HONDA, KATSUHIKO SASAKI, MASATO TAMAYAMAAmerican Society for Composites 2021 2021年09月20日Aircraft flight control usually requires driving flaps and ailerons. However, the air drags increase significantly due to the corners of flaps and aileron. Especially, the gap between mother wing and flap / aileron causes a drag increase. Therefore, studies are being conducted on morphing wings that smoothly and greatly deform the wing surface. For aircraft wing, it is needless to say that strength is important to sustain lift and drag for the aircraft during the flight. For morphing wings, in addition, actuators must be mounted inside the wing to enable the morphing deformation. Moreover, for the aircraft wing, weight is quite important. Therefore, carbon fiber reinforced plastic (CFRP) is currently most suitable for aircraft wing structural materials. However, it is difficult to mold CFRP so that it has sufficient strength and can be morphed. In this study, by using CFRP, the morphing wing structure was prototyped with targeting a small unmanned aerial vehicle (UAV) weighing 3 kg. The CFRP lattice structure that enables morphing deformation was designed and manufactured by applying the electrodeposition resin molding (ERM) method which was developed by the authors. In the ERM method, firstly, the carbon fiber was fixed with a jig according to the designed morphing wing structure, and immersed in the electrodeposition solution. Secondly, the epoxy polymer particle in the solution were electrophoresed and impregnated between carbon fibers. After thermal curing, the morphing wing structure was fabricated. Further, the loading-unloading torsion and bending tests of the morphing wing structure were carried out. Smooth morphing deformation and sufficient strength were confirmed.
- Michio Innami, Shinya Honda, Katsuhiko Sasaki, Yoshihiro NaritaComposite Structures 114400 - 114400 2021年07月 [査読有り]
- Kazuaki Katagiri, Shinya Honda, Toshihiko Okumura, Shimpei Yamaguchi, Sonomi Kawakita, Kazuhiro Kume, Katsuhiko SasakiMechanics of Advanced Materials and Structures 29 26 1 - 8 2021年06月07日An efficient method to increase specific strength of carbon fiber reinforced plastics (CFRP) by using cellulose nanofibers (CNFs) was developed. Eliminating a complex hydrophobic treatment of CNF by using aqueous electrodeposition solution (EDS) containing a polymer with epoxy group, the CFRP with CNF/resin layer was fabricated. The effects of the CNF/resin layer on the bending properties of CFRP were clarified by varying the weight fractions of CNF. The specific flexural rigidity and strength of the CFRP with CNF/resin layer were increased to approximately 3.5 times and 1.8 times those of the CFRP without CNF/resin layer, respectively.
- 茅野 皓輝, 本田 真也, 片桐 一彰, 佐々木 克彦, 武田 量Dynamics & Design Conference 2021 129 一般社団法人 日本機械学会 2021年The aim of this study is to design an optimum CFRP lattice structure for application to a morphing wing. The ground structure based topology method is adopted as the optimization method, and the results are validated by experiments. In this study, to confirm the effectiveness of the optimization method, a simple hook shape was optimized and its stiffness and strength was compared by tensile tests. A 3D printer capable of laminating thermoplastic CFRP was used to fabricate the specimen. The results of tensile tests showed that the optimized specimens exhibited higher stiffness and strength than the reference model, confirming the effectiveness of the proposed method.
**A Pilot Study on Pressure, Flow Rate and Wall Shear Stress within Healthy, Stanford A and B type Aortas using Open Source CFD**Ryo Takeda, Fumiya Sato, Hiroichi Yokoyama, Katsuhiko Sasaki, Nobuyuki Oshima, Akiyoshi Kuroda, Hideyoshi Takashima, Chenyu LiAnnals of Vascular Surgery 2021年 [査読有り]**Effects of cellulose nanofiber content on impact properties of carbon fiber reinforced plastics with the cellulose nanofiber dispersion layer**Kazuaki Katagiri, Naoko Kishimoto, Toshihiko Okumura, Sonomi Kawakita, Shinya Honda, Katsuhiko SasakiMechanics of Advanced Materials and Structure 2021年 [査読有り]**Enhancement of impact properties of CFRP by inserting the non-hydrophobized cellulose nanofiber dispersion layer using an aqueous solution of epoxy resin**Kazuaki Katagiri, Toshihiko Okumura, Sonomi Kawakita, Hirosuke Sonomura, Shinya Honda, Katsuhiko SasakiMechanics of Advanced Materials and Structures 2021年 [査読有り]- Kohei FUKUCHI, Ken-ichi OHGUCHI, Katsuhiko SASAKI, Yorimasa TSUBOTA, Takuro MITA, Wataru NAGAI, Kouji OHSATO, Nobuaki SHINYATransactions of the JSME (in Japanese) 87 895 20 - 00378 2021年 [査読有り]
- Kazuaki Katagiri, Shinya Honda, Shota Nakaya, Takahiro Kimura, Shimpei Yamaguchi, Hirosuke Sonomura, Tomoatsu Ozaki, Sonomi Kawakita, Mamoru Takemura, Katsuhiko SasakiComposites Part A 143 106271 - 106271 2021年 [査読有り]
- Hiraku Takisawa, Naoki Hashimoto, Shinya Honda, Kazuaki Katagiri, Katsuhiko Sasaki, Ryo Takeda15th International Conference on Motion and Vibration Control, MoViC 2020 2020年12月07日The present paper investigates the vibration characteristics of CFRPs including the anisotropic damping properties. Carbon fiber (CF) preforms are prepared by a tailored fiber placement (TFP) machine, and the electrodeposition resin molding (ERM) method is used to impregnate the resin into CF preforms. CFRP plates are fabricated by two different methods which are the ERM and vacuumed assisted resin transfer molding (VaRTM), and experimental modal analysis is conducted to compare the vibration characteristics of those plates. The experimental results show plates fabricated by the ERM exhibit higher damping properties than those by VaRTM. Then, anisotropic damping properties of the present CFRP plates composed of plain weave layers and TFP layers are identified using the finite element analysis (FEA) with the experimental results. In this analysis, the damping properties are modeled by specific damping capacity (SDC) that is defined as the ratio of the dissipated energy and the maximum strain energy in one cycle of loading. Those parameters are determined by minimizing the difference between modal SDCs calculated by the FEA and measured by the experiment. To solve the minimization problem, particle swarm optimization (PSO) is used. Obtained damping parameters enable us to design damping properties more flexibly for CFRPs with arbitrarily shaped fibers.
- Kazuaki Katagiri, Tsuyoshi Totani, Takuya Isono, Ryohei Goto, Shimpei Yamaguchi, Sonomi Kawakita, Tomoatsu Ozaki, Hirosuke Sonomura, Sayaka Minami, Shinya Honda, Katsuhiko SasakiJournal of Energy Storage 31 101636 - 101636 2020年10月 [査読有り][通常論文]
- Kazuaki Katagiri, Shinya Honda, Sayaka Minami, Daiki Kimu, Shimpei Yamaguchi, Takuya Ehiro, Ozaki Tomoatsu, Hirosuke Sonomura, Sonomi Kawakita, Mamoru Takemura, Yayoi Yoshioka, Katsuhiko SasakiMechanics of Advanced Materials and Structures 28 18 1541 - 1550 2020年 [査読有り][通常論文]

© 2018, © 2018 Taylor & Francis Group, LLC. The I-shaped cross-sectional beam of CFRP (CFRP I-beam) is usually manufactured by the continuous protrusion method. Carbon fibers can only be arranged in the longitudinal direction. The CFRP I-beam with arbitrary arrangement of carbon fiber was manufactured with applying the electro-activated deposition molding method. The carbon fiber fabric was immersed in the deposition solution and energized, epoxy resin precipitated around carbon fiber and impregnated. The resin-impregnated fabric was installed to the mold, and the CFRP I-beam was fabricated. The CFRP I-beam was subjected to three-point bending tests, and the relationship between load-deflection was simulated by finite-element analysis. - 瀧澤 拓, 本田 真也, 片桐 一彰, 佐々木 克彦, 武田 量Dynamics & Design Conference 2020 105 - 105 一般社団法人 日本機械学会 2020年
Our previous research found that CFRPs fabricated by the electrodeposition resin molding (ERM) method exhibited high damping properties. In this research, tailored fiber placement (TFP) was used to make curved fiber shapes, however, those shapes were limited to a parabola and a sine curve. Linear combination of radial basis functions (RBFs) were used to make more complex fiber shapes, and optimum fiber shapes are investigated to improve damping of CFRPs fabricated by the ERM method. Damping is modeled by the specific damping capacity (SDC) which is defined as the ratio of dissipated energy and maximum strain energy, and total damping properties of CFRPs are calculated using finite element analysis (FEA). Before optimization, material SDCs of a plain weave sheet and a TFP layer, which are compositions of CFRPs, are identified by particle swarm optimization (PSO) using the results of experimental modal analysis and FEA. Then, fiber shapes were optimized to maximize the first modal SDC of L-shaped and T-shaped plates using PSO with nonlinear dissipative term. Simultaneously, the thickness distribution which is caused by overlaps or gaps between curved fibers was estimated and applied to a finite element model for more accurate numerical estimation. The results showed that the present optimization of curved fiber shapes including estimation of thickness distribution improves the first modal SDC and decreases the volume of a TFP layer in comparison with unidirectional fiber shapes.

- Kazuaki Katagiri, Shimpei Yamaguchi, Sonomi Kawakita, Shinya Honda, Katsuhiko Sasaki, Nozomu Kogiso, Masato TamayamaAIAA Scitech 2020 Forum 1 PartF 2020年© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. The fixed-wing UAV is recently increasing for various missions. For an efficient flight of the UAV, a morphing wing is expected. In this study, the twist morphing wing that deforms entire surface was focused. The twist morphing wing using the Z-shaped cross-sectional spar (Z-spar) was designed and fabricated by CFRP with applying the electrodeposition resin molding (ERM) method. The ERM method, which was developed by the authors, is suitable for the integral molding of three-dimensional structure of CFRP since the resin is impregnated between carbon fibers in the electrodeposition solution. The frontward structure of the morphing wing consisting of the leading edge and Z-spar could be integrally molded by ERM method. Also, for the backward of the wing, CFRP thin plates fabricated by ERM method were installed for upper and lower surface. The plates next to each other were partially overlapped with imitating the bird's feathers. Additionally, the twist morphing wing was installed to the UAV and the aerodynamic performances were evaluated by the wind tunnel test. As a result, the effect of the morphing on the aerodynamic performances was confirmed.
**Effect of Surface Treatment and Cutting Orientation to the Changes in Stents Surface Roughness**Achmad Syaifudin, Julendra Bambang Ariatedja, Katsuhiko SasakiKey Engineering Materials 100980 867 125 - 133 2020年 [査読有り]**Forming state recognition in deep drawing process with machine learning**Tomohiro Tsuruya, Musashi Danseko, Katsuhiko Sasaki, Shinya Honda, Ryo TakedaJournal of Advanced Mechanical Design, Systems, and Manufacturing 13 3 2019年09月 [査読有り][通常論文]**Fabrication of heat-storable CFRP by incorporatingtrans-1,4-polybutadienewith the application of the electrodeposition resin molding method**Kazuaki Katagiri, Ryohei Gotoh, Tsuyoshi Totani, Takuya Isono, Shimpei Yamaguchi, Takuya Ehiro, Hirosuke Sonomura, Tomoatsu Ozaki, Sonomi Kawakita, Yayoi Yoshioka, Sayaka Minami, Shinya Honda, Katsuhiko SasakiJournal of Energy Strage 26 100980-1 - 100980-6 2019年09月 [査読有り][通常論文]- Kazuaki Katagiri, Shinya Honda, Sayaka Minami, Shimpei Yamaguchi, Sonomi Kawakita, Hirosuke Sonomura, Tomoatsu Ozaki, Sohei Uchida, Masayuki Nedu, Yayoi Yoshioka, Katsuhiko SasakiComposites Part A: Applied Science and Manufacturing 123 320 - 326 2019年08月 [査読有り][通常論文]

© 2019 Elsevier Ltd Cellulose nanofibers (CNFs) have high strength. Therefore, many studies have been conducted to improve the mechanical properties of carbon fiber reinforced plastics (CFRP) by dispersing CNF in the matrix. However, since CNFs are hydrophilic, a hydrophobic treatment is required. Previously, authors showed the bending strength of CFRP could be enhanced by CNFs without a hydrophobic treatment. Applying the electro-activated deposition resin molding (ERM) method to fabricate CFRP, CNFs can be applied on the surface since the electro-activated deposition solution is essentially water-based and contains a polymer with epoxy groups. In this study, the CNF sheet was prepared by drying CNF dispersion in advance. Shortly after the ERM, the CNF sheet was applied to the surface of the CFRP. The mechanical properties of the CFRP were enhanced, the maximum elastic modulus and tensile strength were 2.3 times and 1.7 times of the CFRP specimen without the CNF sheet, respectively. - Kazuaki Katagiri, Katsuhiko Sasaki, Shinya Honda, Sayaka Minami, Shimpei Yamaguchi, Takuya Ehiro, Tomoatsu Ozaki, Hirosuke Sonomura, Sonomi Kawakita, Sohei Uchida, Masayuki Nezu, Yayoi YoshiokaComposites Science and Technology 169 203 - 208 2019年01月05日 [査読有り][通常論文]

© 2018 Elsevier Ltd Cellulose nanofiber (CNF) is high strength and lightweight, additionally, it is produced by sustainable natural resources such as wood. Therefore, it has been reported the mechanical properties of CFRP can be improved by dispersing CNF in the matrix. However, as CNF is hydrophilic, a hydrophobic treatment was applied in many previous studies. For efficient CFRP manufacturing, the authors have developed an electrochemical resin molding method by using aqueous electro-activated deposition which contains the polymer having an epoxy group. In this method, the carbon fiber fabric is immersed in the electro-activated deposition solution and energized, epoxy resin is precipitated around the carbon fiber and impregnated. In this study, shortly after electro-activated deposition, CNF without a hydrophobic treatment was applied to the surface of the resin-impregnated carbon fiber fabric. The mechanical properties of CFRP could be enhanced, and optimum weight fraction of CNF was revealed. - Kazuaki Katagiri, Shinya Honda, Sayaka Minami, Shimpei Yamaguchi, Hirosuke Sonomura, Ozaki Tomoatsu, Sonomi Kawakita, Sohei Uchida, Masayuki Nezu, Mamoru Takemura, Yayoi Yoshioka, Katsuhiko SasakiMechanics of Advanced Materials and Structures 28 11 1089 - 1097 2019年 [査読有り][通常論文]

© 2019, © 2019 Taylor & Francis Group, LLC. Many researches on strengthening the matrix of Carbon Fiber Reinforced Plastic (CFRP) using cellulose nanofibers (CNFs) have been reported. However, hydrophobic treatment to modify the surface of CNFs is indispensable. Authors previously showed that the bending properties of CFRP were enhanced by CNF without hydrophobic treatment after the electro-activated deposition resin molding (ERM) method. CNF can be dispersed on the surface of CFRP since the electro-activated deposition solution is water based. In this study, first, it was confirmed that the tensile properties of CFRP could be enhanced by CNF dispersed on the surface after the ERM method. Also, the weight fraction of CNF was optimized to maximize the tensile properties. Second, the I-shaped cross-sectional beam (I-beam) was molded by laminating the CFRP with CNF dispersed on the surface. It was confirmed that the bending properties of the CFRP I-beam was enhanced by CNF, and the effect of CNF on the interlaminar strength was evaluated. **Fatigue life estimation of SAC solder based on inelastic strain analysis using stepped ramp wave loading**Ken-ichi Ohguchi, Katsuhiko Sasaki, Yuki Yuze, Kohei FukuchiMechanical Engineering Journal 19 2019年 [査読有り][通常論文]- Satoru TAMAKI, Shinya HONDA, Yohei HOSHINO, Katsuhiko SASAKI, Ryo TAKEDAThe Proceedings of the Dynamics & Design Conference 2019 102 - 102 2019年
- 橋本 直暉, 本田 真也, 片桐 一彰, 佐々木 克彦, 武田 量, 山口 真平, 川北 園美Dynamics & Design Conference 2019 103 一般社団法人 日本機械学会 2019年 [査読無し]

An autoclave molding with prepregs is the most general method of CFRP manufacturing. It is well known that this method is time and energy consuming and prevents the cost reduction of CFRPs. Therefore, aiming to improve CFRP productivity, some manufacturing methods without the autoclave have been proposed such as a vacuumed resin transfer molding（VaRTM）method. The authors have been also proposed a new CFRP manufacturing method that is an electro deposition resin molding（EDRM）method. The EDRM is an application of the electro deposition technology which has been used as a coating technology for automobiles, and it is suitable for mass productions. In our previous studies, static mechanical properties including stiffnesses and strength of CFRPs molded by the EDRM have been investigated, but their dynamic properties have not been done yet. Therefore, in this study, in order to evaluate the vibration characteristics of CFRPs produced by the EDRM, an experimental modal analysis and finite element analysis（FEA） were performed on CFRP specimens with straight and curved reinforcing fibers. The specimens were also manufactured by the VaRTM method and their vibration damping characteristics were compared. It was confirmed from numerical and experimental results that natural frequencies and eigenmode shapes agree well with high accuracy, and the FEA is useful for the specimen manufactured by the EDRM. It is also found that CFRPs produced by the EDRM has greater modal damping ratios than CFRPs by the VaRTM. - Kazuaki Katagiri, Shinya Honda, Daiki Kimu, Shimpei Yamaguchi, Tomoatsu Ozaki, Hirosuke Sonomura, Sonomi Kawakita, Sohei Uchida, Masayuki Nezu, Mamoru Takemura, Yayoi Yoshioka, Katsuhiko SasakiProceedings of the American Society for Composites - 34th Technical Conference, ASC 2019 2019年 [査読有り][通常論文]

© 2019 by DEStech Publications, Inc. and American Society for Composites. All rights reserved. The strength enhancement of the matrix of CFRP has been a major research subject. In particular, strength of the surface resin layer of CFRP is quite important since the bending stress is most effective on the surface but also exposed to foreign object debris (FOD). One of the methods to strengthen resin matrix of CFRP is to disperse cellulose nanofibers (CNF), therefore, many studies have been conducted. However, due to hydrophilicity of CNF, a hydrophobic treatment is indispensable. Although various hydrophobic methods have been proposed, special chemical substances are required and resulted in higher manufacturing costs. In previous study, authors showed that the mechanical properties of CFRP were enhanced by CNF without hydrophobic treatment using the electro-activated deposition resin molding (ERM) method. In the ERM method, a non-crimp carbon fiber fabric (NCF) is immersed in the electro-activated deposition solution which contains polymer with epoxy group. Then, by energization, the resin precipitates around the carbon fiber and is efficiently impregnated to the NCF in the solution. After the ERM, CNF can be applied on the surface of CFRP since the electro-activated deposition solution is water-based. After thermal curing, CNF is embedded on the surface resin layer of CFRP. In this study, the analysis to understand the effect of CNF on the mechanical properties was carried out. As a practical application, the I-shaped cross-sectional beam (I-beam) was selected for the analysis. It was experimentally revealed that the bending strength of I-beam was enhanced by embedding of CNF. With assumed the material constants based on the tensile tests of the CFRP, the bending properties with dispersing CNF on the surface were analyzed by using the finite element method. As a result, the relationship between load and deflection could be well simulated, and the effect of CNF on the bending properties was clarified. **Vulnerability analysis on the interaction between Asymmetric stent and arterial layer,” Bio-medical materials and engineering**Achmad Syaifudin, Julendra B. Ariatedja, Yusuf Kaelani, Ryo Takeda, Katsuhiko SasakiBio-medical materials and engineering 30 3 309 - 322 2019年 [査読有り][通常論文]- Kazuaki Katagiri, Shinya Honda, Sayaka Minami, Yusuke Tomizawa, Daiki Kimu, Shimpei Yamaguchi, Takuya Ehiro, Tomoatsu Ozaki, Hirosuke Sonomura, Sonomi Kawakita, Mamoru Takemura, Yayoi Yoshioka, Katsuhiko SasakiCOMPOSITE STRUCTURES 207 658 - 664 2019年01月 [査読有り][通常論文]

For the efficient manufacturing of carbon fiber reinforced plastics (CFRP), the electro-activated deposition resin molding (ERM) method is developed. The carbon fiber fabric is immersed in an electro-activated deposition solution containing polymer with epoxy groups. By energization, an epoxy resin is precipitated on the surface of the carbon fiber, and impregnation occurred in the solution. In this study, applying the ERM method, CFRP specimen with the hole was manufactured. Furthermore, the reinforcement by arranging the fiber circumferentially around the hole was installed. The carbon fiber fabric was sewn using the tailored fiber placement (TFP) machine. As a results, the effect of the reinforcement was confirmed. The tensile strength of CFRP with the hole and the reinforcement was the same as in the case without the hole. From the finite element analysis, it was confirmed that the reinforcement around the hole reduced the stress concentration. **Efficient manufacturing method of CFRP corrugation by using electro‐activated deposition resin molding**Kazuaki Katagiri, Shinya Honda, Shimpei Yamaguchi, Takuya Ehiro, Sonomi Kawakita, Hirosuke Sonomura, Tomoatsu Ozaki, Yayoi Yoshioka, Mamoru Takemura, Sayaka Minami, Katsuhiko SasakiProceedings of ASC 33rd Annual Technical Conference/18th US-Japan Conference on Composite Materials #14 2018年09月 [査読有り][通常論文]- Hiroto Kontani, Toko Tokunaga, Munekazu Ohno, Katsuhiko Sasaki, Kiyotaka MatsuuraNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals 82 5 125 - 129 2018年 [査読有り][通常論文]

Unidirectional orientation of the carbon fiber is essential in the fabrication of Cucarbon fiber composites with high thermal conductivity, because the fiber exhibits its very high thermal conductivity only in the longitudinal direction. In this study, hot extrusion of a mixture of Cu powder and carbon fiber was applied to fabricate the unidirectionally orientated carbon fiber reinforced Cubased composite and the effects of the volume fraction of carbon fiber on the thermal conductivity have been investigated. It has been demonstrated that hot extrusion of the Cu powdercarbon fiber mixture successfully align the fiber to orient along the extrusion direction, and consequently, the thermal conductivity in this direction increases with the volume fraction of carbon fiber. For the composite with more than 30 vol％ carbon fiber, the application of ultrasonic vibration treatment to the powderfiber mixture is effective for improving the homogeneity of the mixing and hence increasing the relative density and the thermal conductivity of the composite. - 片桐 一彰, 佐々木 克彦, 本田 真也, 南 沙也加, 金 大貴, 山口 真平, 永廣 卓哉, 園村 浩介, 尾崎 友厚, 川北 園美, 木村 貴広, 武村 守, 吉岡 弥生年次大会 2018 J0430303 一般社団法人 日本機械学会 2018年 [査読無し]

For an efficient manufacturing method of CFRP, the electro-activated deposition molding method was developed. In this method, the carbon fiber fabric with curvilinear carbon fiber arrangement could be easily manufactured. The arbitrary arrangement of carbon fiber fabric can be woven by using embroidery machine, and was immersed in an electrodeposition solution containing an epoxy group and energized. Resin could be impregnated, after heat curing, CFRP was obtained. Impregnation is occurred in liquid, therefore, pressurizing process can be eliminated. So, autoclave became unnecessary, neither vacuum packing nor vacuum resin injection like VARTM (Vacuum assisted Resin Molding) method was required. In this study, tensile strength tests were conducted on the three kinds of CFRP specimens, with straight carbon fiber without hole, with hole in the center of specimen, and with controlling carbon fiber direction along principle stress. As a result, the maximum stress of the specimen with hole decreased to 82% of without hole. In case of the specimen with controlling carbon fiber direction along principle stress, the maximum stress recovered to 91% of without hole. **Development of asymmetric stent for treatment of eccentric plaque**Achmad Syaifudin, Ryo Takeda, Katsuhiko SasakiBio-Medical Materials and Engineering 29 299 - 317 2018年 [査読有り][通常論文]**Tmperature dependence on thermal and strength properties of aluminum based high thermal conductive composites containing VGCF-CNT fillers**Kohei Fukuchi, Katsuhiko Sasaki, Terumitsu Imanishi, Ryo TakedaBio-Medical Materials and Engineering DOI:10.1299/mej.18-00001 2018年 [査読有り][通常論文]**Deformation Analysis of Self-Expanding Stent Considering Plaque and a New Expanding Mechanism**Katsuhiko Sasaki, Yukiko Tomook, Ryo Takeda, Achmad SyaifudindEPI International Journal of Engineering 1 1 98 - 106 2018年 [査読有り][通常論文]- Kazuaki Katagiri, Katsuhiko Sasaki, Shinya Honda, Hikaru Nakashima, Yusuke Tomizawa, Shimpei Yamaguchi, Tomoatsu Ozaki, Hirosuke Sonomura, Atsushi KakitsujiCOMPOSITE STRUCTURES 182 666 - 673 2017年12月 [査読有り][通常論文]

A more efficient manufacturing process for CFRP is expected to save energy, time and cost for production. However, it is difficult to impregnate the resin efficiently and uniformly between the carbon fibers, micro void tend to remains and strength decreases. In this study, a novel manufacturing method of CFRP by using the electro-activated deposition resin molding was developed. The non-crimp carbon fiber fabric was immersed in the electro-activated deposition solution, that containing epoxy groups. And, the fabric was energized and heat cured. The electro-activated deposition conditions and tensile properties were investigated for the CFRPs. It was confirmed that resin could be impregnated for multiple plies of the non-crimp carbon fiber fabric without using autoclave and injecting viscous resin like VARTM. Comparing to the traditional manufacturing process, a step of previously mixing an epoxy resin prepolymer and a curing agent was not required. And, a process of vacuum suction could be eliminated, so, wrapping non-crimp carbon fiber fabric with vacuum bag was not necessary. - Kazuaki Katagiri, Katsuhiko Sasaki, Shinya Honda, Hikaru Nakashima, Shimpei Yamaguchi, Tomoatsu Ozaki, Hirosuke Sonomura, Atsushi KakitsujiCOMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 102 108 - 116 2017年11月 [査読有り][通常論文]

Recently, theoretical and experimental methods were proposed for organizing carbon fibers in straight and curvilinear arrangements to obtain a uniform stress distribution in the design of three-dimensional (3D) carbon fiber reinforced thermosetting plastic (CFRP). In this study, to establish an efficient CFRP manufacturing method and realize the curvilinear arrangement of carbon fibers, we develop an electrodeposition resin molding technique. That is, immersing a noncrimp fabric in the electrodeposition solution and energizing electricity, the fabric is impregnated by the resin; thus, a CFRP with curvilinear carbon fibers can be efficiently produced without autoclaving and vacuum packing. We then confirm the optimal electrodeposition conditions for maximizing the tensile strength of the CFRP, and obtain the 3D shape of the CFRP by keeping the noncrimp fabric in solution along the mold. (C) 2017 Elsevier Ltd. All rights reserved. - Achmad Syaifudin, Ryo Takeda, Katsuhiko SasakiThe International Journal of Mechanical Engineering and Sciences 1 1 1 - 7 2017年03月 [査読有り][通常論文]
- Y. Yanagisawa, Y. Kishi, K. SasakiSTRENGTH OF MATERIALS 49 2 239 - 249 2017年03月 [査読有り][通常論文]

The long cooling time during heat treatment of a large forging due to mass effect leads to the creep deformation at not only high temperature but also transformation temperature ranges. Therefore, both the transformation plasticity and the creep together with the phase transformation significantly affect the stress distribution of the forging after the heat treatment. In this study, a FEM model considering both the transformation plasticity and creep was developed. Proposed model was integrated into commercial FEM codes ANSYS via user subroutines. The material properties of the transformation plasticity and creep were also measured experimentally. For experimental verification, the residual stress measurements of the large forged shaft are compared with those of the simulations. The simulations show that the residual stresses were mainly caused by the phase transformation stress. In particular, it is found that both the transformation plastic strain and the creep strain play important roles in simulating the residual stress during heat treatment of a large forged shaft. - 片桐 一彰, 佐々木 克彦, 本田 真也, 冨沢 祐介, 南 沙也加, 山口 真平, 永廣 卓哉, 尾﨑 友厚, 園村 浩介, 吉岡 弥生, 垣辻 篤M&M材料力学カンファレンス 2017 OS1023 一般社団法人 日本機械学会 2017年 [査読無し]

High strength properties of cellulose nanofiber (CNF) are well known, and it has also been already reported that the strength of CFRP could be improved by dispersing CNF in the matrix resin. However, in the previous work, hydrophobic treatment was required to disperse CNF due to its hydrophilicity. In this study, based on a novel manufacturing method of CFRP by using electro-activated deposition resin molding, CNF without hydrophobic treatment was well dispersed on the surface of CFRP. The process was, firstly, the non-crimp carbon fiber fabric was immersed in an electro-activated deposition solution which includes epoxy groups. And, the fabric was electrically energized and electrodepositioned. Secondly, the CNF dispersion was applied and coated to the surface of CFRP. The electrodeposition solution used in this method is an environmentally friendly aqueous solvent. CNF has good dispersibility in water, hydrophobic treatment was not necessary. After heat curing, the three-point bending test was conducted to confirm the strength properties. As a result, it was found that the flexural modulus was improved by 49% and the bending strength was improved by 41%, comparing to the CFRP without CNF on the surface. - Atsuko Takita, Katsuhiko Sasaki, Ken Ichi Ohguchi, Hiroyuki FujikiKey Engineering Materials 734 251 - 259 2017年 [査読有り][通常論文]

In design of the electronic device, FEM analyses considering the creep deformation of solder joints in-situ should be conducted to evaluate the strength reliability. The indentation test is one of effective method to evaluate the creep deformation in microscopic region. However, the result obtained by the indentation test does not coincide with that obtained by the tensile creep test. To solve the problem, the method to determine the suitable area for the indentation test had also been proposed by using the numerical test. To apply the proposed method for the actual indentation test, the homogeneity of specimen should be considered. In this paper, the analyses of the proposed indentation tests were conducted by using the homogeneous and inhomogeneous specimen models of Sn-3.0Ag-0.5Cu. Three types of the deformation behavior were given for the initial phase and the indenter was pushed into in the specimen at the three locations. As a result, it was found that there was not difference in the distribution of the principal stress caused by variation in the indent location. However, the proposed method can successfully determine the reference area except for the case when the deformation behaviors of the constituent phases have a large difference. - Toko Tokunaga, Koichi Takahashi, Munekazu Ohno, Katsuhiko Sasaki, Terumitsu Imanishi, Kiyotaka MatsuuraMATERIALS TRANSACTIONS 58 6 938 - 944 2017年 [査読有り][通常論文]

New heatsink materials having higher thermal conductivities have recently been required due to the recent rapid improvements in performance of the central processing unit, CPU, with increasing heat generation from computer devices. As an alternative material to conventional heatsink materials such as Al and Cu, composites containing carbon fibers have recently been gaining much attentions because of their extremely high thermal conductivity. However, carbon fiber exhibits high thermal conductivity only in its longitudinal direction. Therefore, it is essential to control the orientation of the carbon fibers in the composite materials. In the present study, hot extrusion of a powder-fiber mixture is applied to realization of unidirectional array of carbon fibers in Al matrix, and the effects of volume fraction of the carbon fibers on the thermal conductivity of the carbon fiber oriented Al-based composite have been investigated. It has been demonstrated that the carbon fibers are unidirectionally oriented in the extrusion direction, and the thermal conductivity in this direction increases with the increase in volume fraction of the carbon fibers. For the composites with more than 30 vol% of carbon fibers, the addition of Al-Si alloy powder or the application of the spark plasma sintering, SPS, before the extrusion was found to be effective for improving the sinterability of the powder-fiber mixture. - Yusuke Tomizawa, Takehito Suzuki, Katsuhiko Sasaki, Ken-Ichi Ohguchi, Daisuke EchizenyaKey Engineering Materials 725 299 - 304 2017年 [査読有り][通常論文]

Recently, Halt (Highly accelerated limit test) is widely employed for evaluation of reliability of electronic products. Halt condition is quite severe. The tested products are subjected to mechanical impacts, thermal shock, and vibration at same time. However, there has not been a reasonable and accurate evaluation method for Halt yet. To construct an accurate evaluation method of Halt, basic deformation mechanism of parts of the electronic products should be clarified from both experimental and theoretical points of view. In this paper, focusing on solder joints of circuit boards of electronic products, ratchetting deformation, especially, biaxial ratchetting deformation of solder joints is revealed from both experimentally and theoretically. The authors have already conducted biaxial ratchetting test combining axial and torsional cyclic loading using a tubular specimen of Type 304 stainless steel. However, as for solders, it is difficult to make tubular specimen. Since size of the solder joints is micron, a small size joint specimen of copper tube and solder is employed in this paper. First, to confirm the quality of the joint specimen such as boundary between copper and solder, both the tensile and cyclic loading tests are conducted at several temperatures using Sn-3Ag-0.5Cu. The basic characteristic of tensile and fatigue failure is obtained from these tests. After the confirmation of the accuracy of the joint specimen, biaxial ratchetting tests are conducted superposing the tensile load on cyclic torsion. The biaxial ratchetting tests are conducted using a biaxial loading testing machine developed for the joint specimens of solder and copper. - Ken-Ichi Ohguchi, Katsuhiko SasakiKey Engineering Materials 725 305 - 310 2017年 [査読有り][通常論文]

The fatigue tests under both loading conditions of the Fast-Slow and the Slow-Fast were conducted to discuss validity of an inelastic strain analysis method which was proposed previously. The development behaviors of plastic and creep strains during the tests were analyzed by employing the stepped ramp wave (SW) loading. Using the analysis results, the difference of the development behaviors of plastic and creep strains between the Fast-Slow condition and the Slow-Fast condition was clarified. Then, the fatigue failure surfaces obtained from the tests were observed by using SEM to clarify the difference of the fracture surface between the Fast-Slow condition and the Slow-Fast condition. By correlating the aspect of fracture surface with the development behavior of plastic and creep strain, the validity of the proposed inelastic strain analysis method was discussed. - Atsuko Takita, Katsuhiko Sasaki, Ken-Ichi Ohguchi, Hiroyuki FujikiKey Engineering Materials 725 293 - 298 2017年 [査読有り][通常論文]

For accurate evaluation of the reliability of electronic package, FEM analyses considering the creep deformation of solder joint in-situ should be conducted. It is well known that the indentation creep test has an advantage to evaluate the creep deformation in microscopic region although there are the problems. Authors already modified the indentation creep test and proposed the method to estimate the steady state creep deformation by the modified test. For lead free solders generally used for the solder joint, the transient creep deformation should be measured by the indentation test in addition to the steady state creep deformation. The transient creep strain occurs in the indentation process. Therefore, it needs to separate the strain into the elastic-plastic strain and the creep strain. In this paper, the method to obtain the stress-strain relation using the indentation test is proposed. New indentation test used the stepped load was proposed to obtained the stress variation during the indenter was pushed and conducted by the numerical test. The suitable measurement point to obtain the relationship between the stress and the strain was identified. The stress variation estimated by proposed area well coincides with the equivalent stress variation of the nodal solution. Therefore, if the method to obtain the strain variation during the indentation process by the indentation in future is developped, it may be possible to estimate the stress-strain curve expressed the uniaxial deformation in the microscopic region. - Yusuke Yanagisawa, Yasuhiro Kishi, Katsuhiko SasakiKey Engineering Materials 725 647 - 652 2017年 [査読有り][通常論文]

The residual stress distributions of the forgings after both water-cooling and air-cooling were measured experimentally. The residual stress occurring during the heat-treatment was also simulated considering the phase transformation and the transformation plasticity. A comparison of the experiments with the simulations showed a good agreement. These results shows that the transformation plastic strain plays an important role in the heat treatment of large forged shafts. - Yusuke Yanagisawa, Takafumi Hosoya, Yasuhiro Kishi, Katsuhiko SasakiMechanical Engineering Journal 4 4 DOI: 10.1299/mej.17-00266 - 00266-17-00266 一般社団法人 日本機械学会 2017年 [査読有り][通常論文]

Transformation plasticity significantly affects the stress distribution of a forging after heat-treatment. In this study, the transformation plasticity in a multi-phase transformation was measured experimentally. Two kinds of low-alloy steels were used: ASME SA508 and JIS SCM420. The materials were heat treated under different conditions to vary the phase fraction of ferrite. Then the transformation plastic strains of bainite were experimentally identified from the deviation between the stress-free total strain value and the strain value with an applied stress. After the tests were finished, an orientation microscopy was performed using EBSD. The grain average misorientation (GAM) values of the bainite phase become higher than those of the ferrite phase due to the bainite sub-unit. The volume fractions of ferrite were defined as the area lower than the threshold value of the GAM. The transformation plastic strain during the bainite transformation decreased with increasing volume fraction of ferrite. Although there is a quantitative difference in the transformation plastic strains between SA508 and SCM420, the normalized values give the same tendency in both materials. Furthermore, the calculated transformation plasticity using a multi-phase model shows a good agreement with the measurements. This result suggests that the transformation plasticity behavior of the bainite transformation is the same as between a single transformation (bainite) and a double transformation (bainite and ferrite).

- Md Kamrul Hasan, Katsuhiko SasakiJOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 30 7 3085 - 3095 2016年07月 [査読有り][通常論文]

Finite element analysis (FEA) has been carried out with the aim of understanding the thermal deformation characteristics of two solar cell configurations. One of the solar cell models is tabbed by lead-free solder, the other model by Conductive film (CF). A high temperature soldering process could weaken the bond and reduce the reliability of the cells because of the residual stress caused by the different thermal expansion coefficients of the materials. Moreover, solar irradiation generates temperature distribution across the surface of the solar cell, and the development of solar cells made of thinner crystalline silicon wafers will lead to the reduction in manufacturing costs. In this study, Finite element analysis (FEA) of the manufacturing process has been carried out using both solder and CF bonding. Three temperature cycles were applied to analyze different environmental operating conditions and understand how thermal cycles affect the residual stress during actual service conditions. This investigation provides a comparison of thermal deformations between solder and CF bonded solar cells in order to understand which offers substantial reliability in the long term. Also this study explores the effects of various thicknesses of the silicon wafer on the residual stress and deformation of the solar cells. - Yusuke Tomizawa, Katsuhiko Sasaki, Akiyoshi Kuroda, Ryo Takeda, Yoshihiko KaitoAPPLIED THERMAL ENGINEERING 98 320 - 329 2016年04月 [査読有り][通常論文]

As mobile devices become more complex and higher in performance despite the smaller size, heat concentration at localized areas has become a problem. In recent years, passive cooling using phase change materials (PCMs) has drawn attention as a thermal management method for mobile devices. PCMs reduce the temperature increase rate due to their latent heat properties. This reduction in the temperature increase rate is called a "delay effect". Moreover, microencapsulated PCMs (MPCMs) are attracting attention because they keep the melted PCMs from leaking. In this study, PCM sheets containing MPCM/polyethylene composite material are investigated for the thermal management of mobile devices. Namely the authors conduct a series of experiments using the PCM sheet with a high thermal conductivity sheet mounted into a simply modeled mobile device. Effects of the mass, the latent heat, the thermal conductivity, the configuration of the PCM sheet, and high thermal conductivity sheet on the temperature of a smart phone simulator are investigated. A finite element analysis (FEA) is also conducted considering the phase change of PCMs to investigate the optimal dimension and shape of PCMs. As a result, the delay effect of PCMs and the effectivity of a copper sheet pasted on the PCMs are verified by experiments. Moreover, FEA shows that using the PCM sheet with high thermal conductivity sheet has an advantage for the thermal management of mobile devices and gives an optimal condition for the PCM sheets. (C) 2015 Elsevier Ltd. All rights reserved. - 片桐 一彰, 佐々木 克彦, 山口 真平, 垣辻 篤機械材料・材料加工技術講演会講演論文集 2016.24 122 一般社団法人 日本機械学会 2016年 [査読無し]

Application of CFRP is spreading from aircrafts to automobiles. The energy reduction in the manufacturing process of CFRP is strongly requested with the increase of CFRP production volume. So, the Vacuum Assisted Resin Transfer Molding (VaRTM) is becoming the mainstream from Autoclave Molding as the manufacturing method of CFRP. However, even in VaRTM, the interfacial strength between carbon fiber and resin must be improved. It is difficult to control the resin flow to fill all the space in CFRP, therefore, the void is remained slightly on the interfacial surface. Recently, the design of CFRP with optimal arrangement of carbon fiber distribution is progressing including curved line as well as straight. It is possible to weave carbon fiber in any shape, however, using VaRTM, the flow of the resin is deteriorated and CFRP becomes inhomogeneous. In this study, the manufacturing method of CFRP by using electrodeposition was developed. CFRP was manufactured with immersing the woven carbon sheet in the epoxy electrodeposition solution. Electrodeposition conditions were investigated and the tension test was conducted on the CFRP. - 久保田 祥, 佐々木 克彦, 柳沢 祐介, 岸 恭弘北海道支部講演会講演概要集 2016 33 - 34 一般社団法人 日本機械学会 2016年
- 鈴木 健仁, 冨沢 祐介, 佐々木 克彦, 越前谷 大介北海道支部講演会講演概要集 2016 35 - 36 一般社団法人 日本機械学会 2016年
- 廣瀬 諒典, 佐々木 克彦, 武田 量北海道支部講演会講演概要集 2016 31 - 32 一般社団法人 日本機械学会 2016年
- 柳沢 祐介, 小枝日出夫, 佐々木克彦日本機械学会論文集A編 DOI:10.1299/transjsme.15-00520 一般社団法人 日本機械学会 2016年 [査読有り][通常論文]

During heat-treatment when forging a large shaft, stress occurs due to temperature change and phase transformation, and special care should be paid to the heat treatment in order to prevent cracking. Therefore it is important to use the finite element method to estimate the stress and deformation resulting from the heat treatment. However, few previous studies treating large forgings in heat treatment simulations include phase transformation. In this report, the residual stress distribution of the test material after water-cooling and air-cooling was measured based on inherent strains, and heat treatment simulations considering the phase transformation and transformation plasticity were performed. It was found that, especially, the transformation plastic strain plays an important role to simulate the residual stress due to the heat treatment of the large shaft. - Toko Tokunaga, Koichi Takahashi, Munekazu Ohno, Katsuhiko Sasaki, Terumitsu Imanishi, Kiyotaka MatsuuraJOURNAL OF THE JAPAN INSTITUTE OF METALS 80 10 640 - 645 2016年 [査読有り][通常論文]

New heatsink materials having higher thermal conductivities have recently been required due to the recent rapid improvements in performance of the central processing unit, CPU, with increasing heat generation from computer devices. As an alternative material to conventional heatsink materials such as Al and Cu, composites containing carbon fibers have recently been gaining much attentions because of their extremely high thermal conductivity. However, the carbon fiber exhibits high thermal conductivity only in its longitudinal direction. Therefore, it is essential to control the orientation of the carbon fibers in the composite materials. In the present study, hot extrusion of a powder-fiber mixture is applied to realization of unidirectional array of carbon fibers in Al matrix, and the effects of volume fraction of carbon fiber on the thermal conductivity of the carbon fiber oriented Al-based composite have been investigated. It has been demonstrated that the carbon fibers are unidirectionally oriented in the extrusion direction, and consequently, the thermal conductivity in this direction increases with the increase in volume fraction of the carbon fiber. For the composites with more than 30 vol% carbon fiber, the addition of Al-Si alloy powder or the application of the spark plasma sintering, SPS, before extrusion was found to be effective for improving the sinterability of the powder. fiber mixture. - A. Takita, K. Sasaki, K. Ohguchi, R. TakedaEXPERIMENTAL MECHANICS 55 6 1081 - 1091 2015年07月 [査読有り][通常論文]

A method to estimate the creep properties by measuring the micro size deformation is required for the FEM analysis considering the creep deformation of the solder joint in-situ. An indentation creep test is one of the effective methods to directly evaluate the creep deformation of solder joint. However, the indentation test does not give the same creep properties as those obtained by the uniaxial creep tests using a bulk specimen. The authors have proposed an indentation test conducted under the constant depth to determine a suitable reference area, which leads to the same creep characteristics as those obtained by the uniaxial creep test. One of the remaining problems of the indentation test is that the reference area cannot be determined without the creep data obtained by the uniaxial creep test using bulk specimens. In this paper, a series of numerical indentation tests under a constant depth were conducted to construct a method to determine a new reference area without creep data obtained from the uniaxial creep test using bulk specimens. The numerical tests were conducted using finite element method (FEM). The numerical tests showed that the distribution of the principal stress plays an important role to determine the reference area of the indentation tests. Finally, it was found that the reference area obtained considering the distribution of the principal stress gives almost the same creep characteristic as those obtained by the uniaxial creep using bulk specimens. - Katsuhiko Sasaki, Ken-Ichi Ohguchi, Atsuko TakitaAdvanced Structured Materials 64 335 - 356 2015年 [査読有り][通常論文]

An indentation creep test is one of the effective methods to directly evaluate the creep deformation of solder joint. However, the indentation test does not give the same creep properties as those obtained by the uniaxial creep tests using a bulk specimen. In this paper, the authors proposes an indentation test conducted under the constant depth to determine a suitable reference area, which leads to the same creep characteristics as those obtained by the uniaxial creep test. A series of numerical micro indentation tests under a constant depth were conducted to construct a method to determine a new reference area without creep data obtained from the uniaxial creep test using bulk specimens. The numerical tests were conducted using finite element method (FEM). The numerical tests showed that the distribution of the principal stress plays an important role to determine the reference area of the indentation tests. Finally, it was found that the reference area obtained considering the distribution of the principal stress gives almost the same creep characteristic as those obtained by the uniaxial creep using bulk specimens. - Achmad Syaifudin, Ryo Takeda, Katsuhiko SasakiBIO-MEDICAL MATERIALS AND ENGINEERING 25 2 189 - 202 2015年 [査読有り][通常論文]

The physical properties of the stent surface influence the effectiveness of vascular disease treatment after stent deployment. During the expanding process, the stent acquires high-level deformation that could alter either its microstructure or the magnitude of surface roughness. This paper constructed a finite element simulation to observe the changes in surface roughness during the stenting process. Structural transient dynamic analysis was performed using ANSYS, to identify the deformation after the stent is placed in a blood vessel. Two types of bare metal stents are studied: a Palmaz type and a Sinusoidal type. The relationship between plaque length and the changes in surface roughness was investigated by utilizing three different length of plaque; plaque length longer than the stent, shorter than the stent and the same length as the stent. In order to reduce computational time, 3D cyclical and translational symmetry was implemented into the FE model. The material models used was defined as a multilinear isotropic for stent and hyperelastic for the balloon, plaque and vessel wall. The correlation between the plastic deformation and the changes in surface roughness was obtained by intermittent pure tensile test using specimen whose chemical composition was similar to that of actual stent material. As the plastic strain is achieved from FE simulation, the surface roughness can be assessed thoroughly. The study found that the plaque size relative to stent length significantly influenced the critical changes in surface roughness. It was found that the length of stent which is equal to the plaque length was preferable due to the fact that it generated only moderate change in surface roughness. This effect was less influential to the Sinusoidal stent. - Atsuko Takita, Katsuhiko Sasaki, Ken-ichi OhguchiJOURNAL OF ELECTRONIC MATERIALS 43 7 2530 - 2539 2014年07月 [査読有り][通常論文]

For the design of high-density electronic packages, finite element method (FEM) analyses to evaluate strength reliabilities of solder joints should be conducted by employing the material parameters which can precisely reflect the creep properties of solder joints in actual electronic equipment. To obtain accurate results of the structural analyses of the solder joints, a method to evaluate the steady-state creep deformation in situ must be developed. The indentation creep test is an effective method to evaluate the creep properties of the solder joints in situ; however, the creep properties obtained by this method do not give the same results as those obtained by tensile creep tests using bulk specimens. In this paper, the indentation creep test at 1 N loading for 9,000 s duration was experimentally conducted to confirm that the steady-state creep deformation obtained by the indentation creep test did not coincide with that by the tensile creep tests using bulk specimens. To identify the reason, the indentation creep simulation was conducted by FEM analysis. As a result, it was found that the reference area used to obtain the creep strain from the indentation creep test should be modified. A method to obtain the new reference area is proposed from comparisons of experiments with simulations. Finally, this paper shows that the creep properties obtained by the indentation creep test using the new reference area coincided with those obtained by tensile creep tests using bulk specimens. - Daisuke Echizenya, Katsuhiko Sasaki2014 INTERNATIONAL CONFERENCE ON ELECTRONICS PACKAGING (ICEP) 14 - 18 2014年 [査読有り][通常論文]

Recently, solar power generation using crystalline silicon wafers has been rapidly growing. It is well known that the mechanical properties of silicon wafers are affected by defects caused by slicing processes of the wafers. However the effect of the defects on the mechanical properties, especially, strength of the crystalline silicon wafers has not been clarified yet. In this paper, to clarify the effect of the defects during slicing process, bending tests are conducted using defects specimens. The specimens are given a defect by indentations referred to the slicing process of wafers. The two indentation loads are chosen to reveal the effect of the defects size on the bending strength. The bending strength is evaluated using based on fracture mechanics. The residual stress and the initial crack affect the bending strength; therefore, the residual stress and Raman spectrometry of the specimens are measured before the bending tests. Fracture surfaces are also observed by Transmission Electron Microscope (TEM). The experiments show that the bending strength depends on the defects size and that there are numerous cracks on the wafer surface caused by the slicing process. Finally, it is found that the minimizing of the mechanical surface defects on wafers gives the high reliability for photovoltaic modules and the increase in the wafer strength. Furthermore the residual stress and Raman spectrometry show that the difference of surface damage mode caused by the slicing processing method. **Viscoplastic Constitutive Model to Divide Inelastic Strain into Time-Independent and Time-Dependent Strains**OHGUCHI Ken-ichi, SASAKI KatsuhikoAdvanced Materials Modelling for Structures, Advanced Structured Materials 19 296 285 2013年 [査読有り][通常論文]- Katsuhiko Sasaki, Akiyuki Kuroda, Kazuaki Katagiri, Norio Takahashi, Akio Nagai, Yohei Ito, Masateru Takahashi, Yasuhiro Tanaka, Atushi Kakitsuji51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013 2012-1007 1 - 9 2013年 [査読有り][通常論文]

Cooling of Insulated Gate Bipolar Transistors (IGBT) is a huge problem to improve the energy efficiency. To improve the cooling efficiency, a material that has the high thermal conductivity is expected to be employed for the cooling system of IGBT. The authors have fabricated an aluminum based composite material containing a network of vapor grown carbon fiber (VGCF) and carbon nanotube (CNT). The composite has the high thermal conductivity more than three times of pure aluminum. The composite also has the thermal anisotropy caused by VGCF. In this paper, the composite fabricated by authors is employed to a cooling system of IGBT. First, the effect of the thermal conductivity on the thermal efficiency of the cooling system of IGBT is investigated by finite element analyses (FEM). The effect of the thermal anisotropy is, especially, focused on to show the important role of the thermal anisotropy for the cooling system. A method to improve the thermal conductivity of the composite is also shown to decrease the fabrication costs by decreasing in the usage of VGCF. The control of alignments of VGCF is chosen for the method. The alignment is controlled by the contraction flow made by a contraction channel. The experiments show that the contraction flow is effective to control the alignment of VGCF. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. All rights reserved. - 山本 賢, 佐々木 克彦, 片桐 一彰, 今西 輝光, 永井 明夫, 伊藤 洋平, 高橋 教雄, 垣辻 篤機械材料・材料加工技術講演会講演論文集 2013 0 _709 - 1_-_709-4_ 一般社団法人 日本機械学会 2013年 [査読有り][通常論文]
- 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐 一彰, 垣辻 篤M&M材料力学カンファレンス 2013 0 _OS0903 - 1_-_OS0903-3_ 一般社団法人 日本機械学会 2013年 [査読有り][通常論文]

Aluminium (Al) based composites containing vapor-growth carbon fibers (VGCF) and carbon nanotubes (CNT) are fabricated by spark plasma sintering (SPS) in this paper. The thermal conductivity of the composite is three times higher than that of Al material. The composite materials will be able to use as a radiation fin of a heat exchanger and a heatsink. To apply the composites to real used conditions, the strengths and thermal conductivities at several temperatures of the composites should be clarified experimentally. In this paper, therefore, pure tensile tests and laser flash methods are conducted to clarify strength and thermal conductivity of the composites at several temperatures. According to the experimental result, the composite has the different thermal effect on the strength from pure Al. And then the composite has better thermal conductivity than pure Al at high temperature. - 山本 賢, 佐々木 克彦, 黒田 明慈, 武田 量, 片桐 -彰北海道支部講演会講演概要集 2013 0 21 - 22 一般社団法人 日本機械学会 2013年 [査読有り][通常論文]
- 佐々木 克彦, 黒田 明慈, 片桐 一彰, 高橋 教雄, 永井 明夫, 伊藤 洋平, 垣辻 篤機械材料・材料加工技術講演会講演論文集 2012 0 _117 - 1_-_117-4_ 一般社団法人 日本機械学会 2012年 [査読有り][通常論文]

There is an urgent demand to enhance the energy efficiency of various instruments. Carbon fiber-containing aluminum composites are expected to improve the ability of heat dissipation of heat exchanger, and heat sink. Especially, both carbon nanotube (CNT) and vapor-grown carbon fiber (VGCF), which is a kind of carbon fiber, have high thermal conductivities in the axial direction, because of its high aspect ratio. Therefore, alignment of carbon fibers is a key factor to fabricate high thermal conductive composites using CNT and VGCF. In this study, macro- and micro-channels were successfully fabricated and the possibility to control the alignments of VGCF using the contraction of the water flow in the channels was confirmed. The method may have a benefit to fabricate high thermal conductive composites containing CNT and VGCF. - 佐々木 克彦, 福地 孝平, 片桐 一彰, 今西 輝光, 垣辻 篤M&M材料力学カンファレンス 2012 0 _OS0119 - 1_-_OS0119-3_ 一般社団法人 日本機械学会 2012年 [査読有り][通常論文]

This paper evaluates the reliability of an aluminum based composite including vapor growth carbon fibers (VGCF) and carbon nanotubes (CNT). The composite is fabricated using spark plasma sintering and has high thermal conductivity. The correlation between the inelastic deformation and thermal conductivity of the composite is discussed. Specimens made from the composite are first subjected to tensile loading until inelastic strain occurs. After the tensile loading, the thermal conductivities of the specimens were measured to establish the differences in the thermal conductivity before and after the tensile loading. The FEM analyses are also conducted to evaluate the reliability of the composites. It was found that the thermal conductivity changed due to the inelastic deformation of the composites and that a FEM analysis considering the damage due to the deformation qualitatively estimates the differences in the thermal conductivity before and after the tensile loading. - 大野木 成, 佐々木 克彦, 黒田 明慈, 張 旭, 片桐 一彰, 高橋 教雄, 永井 明夫, 伊藤 洋平, 垣辻 篤マイクロ・ナノ工学シンポジウム 2012 0 191 - 192 一般社団法人 日本機械学会 2012年 [査読有り][通常論文]

There is an urgent need to enhance the energy efficiency of various instruments. Carbon fiber-containing aluminum composite is expected to improve the ability of heat dissipation of heat exchanger, and heat sink. Especially, both carbon nanotube (CNT) and vapor-grown carbon fiber (VGCF), which is a kind of carbon fiber, have high thermal conductivity in axial direction, because of its high aspect ratio. Therefore, alignment of carbon fibers is a key factor to fabricate high thermal conductive composites using CNT and VGCF. In this study, a micro-channel was successfully fabricated and the possibility to control the alignments of VGCF using the contraction of the water flow in the micro-channel was confirmed. The method may have a benefit to fabricate high thermal conductive composites containing CNT and VGCF. - FUKUCHI Kohei, SASAKI Katsuhiko, IMANISHI Terumitsu, KATAGIRI Kazuaki, KAKITSUJI AtsushiJournal of Solid Mechanics and Materials Engineering 6 7 801 - 813 一般社団法人 日本機械学会 2012年 [査読有り][通常論文]

This paper evaluates the reliability of an aluminum based composite including vapor growth carbon fibers (VGCF) and carbon nanotubes (CNT). The composite is fabricated using spark plasma sintering and has high thermal conductivity. For the reliability evaluation, the correlation between the inelastic deformation and thermal conductivity of the composite is discussed both with experiments and simulation conducted by the finite element method (FEM). Specimens made from the composite are first subjected to tensile loading until inelastic strain occurs. After the tensile loading, the thermal conductivities of the specimens were measured to establish the differences between the thermal conductivity before and after the tensile loading. The FEM analyses are also conducted to evaluate the reliability of the composites. It was found that the thermal conductivity changed due to the inelastic deformation of the composites and that a FEM analysis considering the damage due to the deformation qualitatively estimates the differences in the thermal conductivity before and after the tensile loading. - Katsuhiko Sasaki, Ken-Ichi OhguchiJOURNAL OF ELECTRONIC MATERIALS 40 12 2403 - 2414 2011年12月 [査読有り][通常論文]

Ratchetting deformation occurring at solder joints in electronic packaging is a concern for electronic devices. Therefore, ratchetting deformation due to thermal cycling at solder joints should be simulated by structural analysis employing tools such as the finite-element method (FEM). However, simulation of ratchetting deformation is difficult, and little modeling to simulate ratchetting deformation accurately has been reported. This work experimentally examines uniaxial ratchetting deformation of Pb-free and Pb-containing solder alloys to elucidate the effect of rate on uniaxial ratchetting. An elasto-plastic-creep constitutive model is developed to simulate uniaxial ratchetting deformation. The constitutive model incorporates a method to determine the material constants simply from a small number of pure tensile tests and subsequent stress relaxation tests. Uniaxial ratchetting deformation of solder alloys was successfully simulated using this constitutive model and simple method for material constant determination. - Daisuke Echizenya, Hiroo Sakamoto, Katsuhiko Sasaki11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 1440 - 1445 2011年 [査読有り][通常論文]

Solar power generation using polycrystalline silicon wafers has been rapidly growing in recent years. As a result, it is required to understand the strength characteristics of polycrystalline silicon wafers in order to enhance their quality. Scratches and material defects should be taken into consideration when strength characteristics of polycrystalline silicon are evaluated, since it is a brittle material. In this paper, bending strength of polycrystalline silicon wafers for solar cells were measured, and evaluation regarding the cause of different strength values, which depend on manufacturing conditions of the wafer, was conducted based on fracture mechanics. Residual stress measurements using Raman spectroscopic and observation with TEM (Transmission Electron Microscope) were also conducted. The results clarified the existence of numerous cracks on the wafer surface that are assumed to be generated during slicing process. Thus, it was confirmed that wafer strength depends on the level of machining damage in slicing process. We can establish high reliability for PV modules as a result of modifying the slicing conditions to minimize the mechanical surface damage on wafers and increase the wafer strength. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - Ken-ichi Ohguchi, Katsuhiko Sasaki11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 1139 - 1144 2011年 [査読有り][通常論文]

Finite element analyses for evaluating fatigue strength of solder joints in electronic packages should employ a constitutive model which can describe cyclic deformations precisely. Therefore, the model should be constructed based on detailed information about the inelastic strain generated under the cyclic loading. We previously investigated both the plastic and creep strains of Sn-Ag-Cu (SAC) lead-free solder under cyclic loading experimentally by conducting cyclic loading tests using stepped ramp waves. In this study, we construct an elastic-plastic-creep constitutive model based on the experimental results, such as the stress-plastic strain relations, and the stress-creep strain relations obtained by the above-mentioned tests. The model considers the characteristics of the plastic and creep deformations in cyclic loading where loading direction changes. Simulations of cyclic loading of the SAC solder under several loading conditions are conducted using the proposed model and the results are compared with experiments. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - Kohei Fukuchi, Katsuhiko Sasaki, Kazuaki Katagiri, Terumitsu Imanishi, Atsushi Kakitsuji11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 1440 - 1445 2011年 [査読有り][通常論文]

This paper treats aluminium (Al) based composites containing vapor-grown carbon fibers (VGCF) and carbon nanotubes (CNT) having very high thermal conductivity. To apply the composites to real used conditions, the interaction between thermal and mechanical properties should be clarified. Therefore, tensile tests are conducted to clarify strength of the composites at several temperatures. The thermal conductivities are measured before and after tensile tests to clarify the dependence of the deformation on the thermal conductivity. Theoretical discussion is also conducted using Nan model and finite element method (FEM). The simulations reasonably explain the deformation dependences of the thermal conductivity of composites. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - SHIMANAKA Kazuya, FUKUCHI Kohei, SASAKI Katsuhiko, KATAGIRI Kazuaki, IMANISHI Terumitsu, KAKITSUJI AtsushiAbstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2011 0 _OS16 - 2-4- 一般社団法人 日本機械学会 2011年 [査読有り][通常論文]
- 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐 一彰, 清水 昭之, 垣辻 篤日本機械学会論文集 A編 77 779 1037 - 1040 一般社団法人 日本機械学会 2011年 [査読有り][通常論文]

Aluminium (Al) based composites containing vapor-grown carbon fibers (VGCF) and carbon nanotubes (CNT) are fabricated by spark plasma sintering (SPS) in this paper. The thermal conductivity of the composite is three times higher than that of Al material. The composite materials will be able to use as a radiation fin of a heat exchanger and a heatsink. To apply the composites to real used conditions, the strength at several temperatures of the composites should be clarified experimentally. In this paper, therefore, pure tensile tests are conducted to clarify strength of the composites at several temperatures. According to the experimental result, the composite has the different thermal effect on the strength from pure Al. And then the interfacial strength between the fibers and the matrix is improved at high temperature. - Zhang Xu, Kuroda Akiyoshi, Sasaki Katsuhiko, KATAGIRI Kazuaki, KAKITSUJI Atsushi年次大会 2011 0 _J043011 - 1-_J043011-5 一般社団法人 日本機械学会 2011年 [査読有り][通常論文]

Simulation of alignment of CNTs or VGCFs by the water contraction flow was carried out. The flow was reproduced using ANSYS CFX software and then the dynamic motion of CNTs transported by the flow was calculated. 2D contraction flow with upstream and downstream channel flows was used. And a CNT was modeled as a dumbbell-like element. The orientation angle of the elements at the end of the downstream flow channel was estimated. It is found that the ratio of upstream channel width to downstream channel width is the major factor for the alignment of the elements. And the absolute value of average angle 0.29 degree and minimum standard deviation 4.98 degree were obtained with upstream channel width 25 cm, contraction length 20 cm, downstream channel length 10 cm, and downstream channel width 1 cm. - Ken-ichi Ohguchi, Katsuhiko SasakiJOURNAL OF ELECTRONIC PACKAGING 132 4 0410003-1 - 0410003-7 2010年12月 [査読有り][通常論文]

We previously proposed an elastic-plastic-creep model to estimate the fatigue strength of lead-free solder joints subjected to cyclic thermal loading. The proposed model requires detailed experimental data regarding the time-independent plastic strain and the time-dependent creep strain during cyclic thermal loading. This paper proposes an experimental method for determining the characteristics of both the plastic and creep strains generated during cyclic loading that employs stepped ramp waves. This method is applied to cyclic tension-compression loadings using a Sn-3.0Ag-0.5Cu lead-free solder for several loading conditions. The method can separate between the time-independent plastic strain and the time-dependent creep strain in cyclic inelastic deformation of solder alloys. [DOI: 10.1115/1.4002897] - Ken-ichi Ohguchi, Katsuhiko SasakiJOURNAL OF ELECTRONIC PACKAGING 132 4 041010-1-041010-7 - 041010-7 2010年12月 [査読有り][通常論文]

The fatigue life of a material varies with the strain rate if it has time-dependent deformation. An interesting phenomenon related to the effect of the strain rate on the fatigue life can be observed when a cyclic tension-compression loading of which strain rate in the tensile region is different from that in the compressive region is employed for the fatigue test. Different fatigue lives due to different strain rates in the tensile and compression regions originate from the difference of development behaviors of creep strain generated in the cyclic loading. This paper investigates the effects of creep strain on the difference of fatigue life due to the different strain rate in the tensile and compression regions. The creep strain of the lead-free solder Sn-3.0Ag-0.5Cu subjected to a cyclic loading was investigated using stepped ramp wave loading. The experimental results reveal that the creep strain develops differently in the tensile and compression regions. A new parameter is proposed for estimating fatigue life when the strain rate varies in the loading direction. [DOI: 10.1115/1.4002911] - Tsuyoshi Takahashi, Katsuhiko SasakiFATIGUE 2010 2 1 767 - 776 2010年 [査読有り][通常論文]

To meet several marketing demands, development of new aluminum alloys which can be used for future high-efficiency diesel engines has been widely pursued. Especially, cylinder heads (hereafter referred to as "head(s)") are used at high combustion pressure and very high temperature, which makes it difficult to achieve a structure with light weight and high rigidity. In this study, aluminum alloy A356 (Al-Si-Mg series) which is a major head material, were conducted the thermal fatigue tests. Thus, the authors focused on the changing of material characteristics (hardness and stress-strain curves as for macroscopic characteristic and microstructure as for microscopic characteristic) during the test. This paper deals with the effects of artificial aging on two aluminum alloys A356, which have been often used for engine cylinder heads. The aluminum alloys were artificially aged under several different conditions after T6 heat treatment. The alloys were tested for fatigue characteristics as thermo-mechanical fatigue failure. The microstructure was observed by TEM to see the effects on microstructure in terms of fatigue failure. In addition, we examined the microstructure of an actual head after a durability test, and tried to find out whether material test conditions above mentioned were reasonable. Finally, the relationship between the microstructure changes and the low cycle thermal fatigue is discussed. (C) 2010 Published by Elsevier Ltd. - FUKUCHI Kohei, SASAKI Katsuhiko, IMANISHI Terumitsu, KATAGIRI Kazuaki, KAKITSUJI Atsushi, SHIMIZU AkiyukiJournal of Solid Mechanics and Materials Engineering 4 8 1273 - 1281 一般社団法人 日本機械学会 2010年 [査読有り][通常論文]

In this paper, the evaluation of the strength of the VGCF/Aluminum composites which have high thermal conductivity is reported. VGCF (Vapor Growth Carbon Fiber) is a kind of the Carbon nanotube (CNT) which has very high thermal conductivity as well as CNT. The composites are made by spark plasma sintering. The stress-strain curves of the composites are obtained by the tensile tests and show that the composites have brittle behavior. The brittleness of the composites increases with increase in the volume fraction of VGCF. A numerical simulation based on the micromechanics is conducted to estimate nonlinear behavior in the elastic deformation and plastic deformation of the stress-strain relations of the composites. The theories of Eshelby, Mori-Tanaka, Weibull, and Ramberg-Osgood are employed for the numerical simulation. The simulations give some information of the microstructural change in the composite related to the volume fraction of VGCF. - 福地 孝平, 佐々木 克彦, 今西 輝光, 清水 昭之, 垣辻 篤, 片桐 一彰計算力学講演会講演論文集 2010 0 595 - 596 一般社団法人 日本機械学会 2010年 [査読有り][通常論文]
- 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐 一彰, 清水 昭之, 垣辻 篤機械材料・材料加工技術講演会講演論文集 2010 0 _220 - 1_-_220-3_ 一般社団法人 日本機械学会 2010年 [査読有り][通常論文]
- Ken-Ichi Ohguchi, Katsuhiko SasakiJournal of Electronic Packaging, Transactions of the ASME 132 4 0410003-1-040003-7 2010年 [査読有り][通常論文]

We previously proposed an elastic-plastic-creep model to estimate the fatigue strength of lead-free solder joints subjected to cyclic thermal loading. The proposed model requires detailed experimental data regarding the time-independent plastic strain and the time-dependent creep strain during cyclic thermal loading. This paper proposes an experimental method for determining the characteristics of both the plastic and creep strains generated during cyclic loading that employs stepped ramp waves. This method is applied to cyclic tension-compression loadings using a Sn-3.0Ag-0.5Cu lead-free solder for several loading conditions. The method can separate between the time-independent plastic strain and the time-dependent creep strain in cyclic inelastic deformation of solder alloys. © 2010 American Society of Mechanical Engineers. - 佐々木 克彦エレクトロニクス実装学会誌 12 7 657 - 657 社団法人エレクトロニクス実装学会 2009年11月01日
- Ken-ichi Ohguchi, Katsuhiko Sasaki, Setsuo AsoJOURNAL OF ELECTRONIC PACKAGING 131 2 2009年06月 [査読有り][通常論文]

This paper proposes a method to estimate basic material constants in an elasto-plastic-creep constitutive model for lead-free solders by conducting only a tensile test. The test employs a stepped ramp wave loading, which repeats instantaneous strain and strain maintenance. Time-independent strains are obtained from the stress-strain relations at the instantaneously strained parts, while the time-dependent strains are obtained from the stress-time relations during the strain maintaining periods. Based on the obtained time-independent and time-dependent strains, the values of the material constants in the elasto-plastic-creep model proposed by the authors are determined. Simulations of the viscoplastic deformations of a Sn-3.0Ag-0.5Cu solder alloy are also conducted to verify the validity of the proposed method. - KOBAYASHI Takuji, SASAKI KatsuhikoJournal of Materials Science: Material in Electronics 20 4 343 - 353 2009年04月 [査読有り][通常論文]

This paper discusses uniaxial ratchetting deformation of lead-free solder alloy Sn-3Ag-0.5Cu and lead-containing solder alloy Sn-37Pb, which were subjected to tension-compression loading with several stress amplitudes and stress ratios, minimum stress over maximum stress. First the uniaxial ratchetting tests were conducted with three maximum stresses and four stress ratios. All tests were conducted using cylindrical bulk specimens of the solder alloys at 313 K. The test results show that there are differences in the ratchetting deformation behavior of the two solder alloys; the larger ratchetting strain occurs in the lead-containing solder alloy than in the lead-free solder alloy. The ratchetting deformation was simulated by the dislocation based constitutive model proposed by Estrin et al. (J Eng Mater Technol 118:441, 1996). The evolution equation of the back stress employed in the constitutive model was modified considering a dynamic recovery term. The effect of the modification of the back stress evolution is discussed by comparing the simulations with the corresponding experimental results. The simulations suggest that the recovery term in the kinematic hardening rule plays an important role in fitting the simulation to the experimental results of the ratchetting deformation of the solder alloys. - 今西 輝光, 佐々木 克彦, 片桐 一彰, 垣辻 篤日本機械学会論文集 A編 75 749 27 - 33 一般社団法人 日本機械学会 2009年 [査読有り][通常論文]

In this paper, vapor-grown carbon fiver (VGCF), which is a kind of carbon nanotubes (CNT), is used for the composite materials with aluminum matrix. It is found out that the thermal conductivity of the composites is about 2.5 times higher than that of the pure aluminum of the matrix if the direction of VGCF is aligned. To improve the thermal conductivity of the composites, small amount of CNT were added to the VGCF filler. The effect of the addition of CNT on the thermal conductivity was examined by both the finite element analysis (FEM) and the measurements of the thermal conductivity. Simulations of finite element analysis (FEM) shows that the possibility to improve the thermal conductivity with small amount addition of CNT because of the cross-link (VGCF-CNT-VGCF). Therefore, small amount of CNT are added to the VGCF/aluminum composites. The thermal conductivity of the composites added CNT have about 20% higher thermal conductivity than that of the composites without CNT. The cross-links of VGCF due to the CNT addition is also confirmed by FE-SEM observation. - Shinya Honda, Yoshihiro Narita, Katsuhiko SasakiADVANCED COMPOSITE MATERIALS 18 4 297 - 314 2009年 [査読有り][通常論文]

A design method is proposed to optimize the stacking sequence of laminated composite plates for desired vibration characteristics. The objective functions are the natural frequencies of the laminated plates, and three types of optimization problems are studied where the fundamental frequency and the difference of two adjacent frequencies are maximized, and the difference between the target and actual frequencies is minimized. The design variables are a set of discrete values of fiber orientation angles with prescribed increment in the layers of the plates. The four lamination parameters are used to describe the bending property of a symmetrically laminated plate, and are optimized by a gradient method in the first stage. A new technique is introduced in the second stage to convert from the optimum four lamination parameters into the stacking sequence that is composed of the optimum fiber orientation angles of all the layers. Plates are divided into sub-domains composed of the small number of layers and designed sequentially from outer domains. For each domain, the optimum angles are determined by minimizing the errors between the optimum lamination parameters obtained in the first step and the parameters for all possible discrete stacking sequence designs. It is shown in numerical examples that this design method can provide with accurate optimum solutions for the stacking sequence of vibrating composite plates with various boundary conditions. (C) Koninklijke Brill NV, Leiden, 2009 - 本田真也, 成田吉弘, 佐々木克彦日本機械学会論文集C編 75 753 1244 - 1250 2009年 [査読有り][通常論文]

A new design method is proposed here to maximize the fundamental frequency of laminated composite plates reinforced by curvilinear fibers. Spline functions represent arbitrarily shaped fibers and Ritz solutions generate frequency equations. The optimum curvilinear shapes are searched for the maximum fundamental frequencies using genetic algorithms, and the increments of data points which define the spline shape are used as design variables under the limited range of undulation. Comparison of the present analysis method gives good agreement with the finite element method in terms of natural frequencies and vibration modes, and the optimized results show that the present plate with optimally shaped curvilinear fibers gives higher or equal fundamental frequencies than those of the conventional plate with optimally oriented parallel fibers. - 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐 一彰, 垣辻 篤, 清水 昭之北海道支部講演会講演概要集 2009 0 139 - 140 一般社団法人 日本機械学会 2009年 [査読有り][通常論文]
- 浅野 佑介, 佐々木 克彦, 福地 孝平, 今西 輝光, 片桐 一彰, 垣辻 篤, 清水 昭之北海道支部講演会講演概要集 2009 0 141 - 142 一般社団法人 日本機械学会 2009年 [査読有り][通常論文]
- 福地 孝平, 今西 輝光, 佐々木 克彦, 片桐 一彰, 垣辻 篤M&M材料力学カンファレンス 2009 0 365 - 367 一般社団法人 日本機械学会 2009年 [査読有り][通常論文]

In this paper, the evaluation of the strength of the VGCF/Aluminum (Al) composites which have highly thermal conductivity is conducted. VGCF (Vapor Growth Carbon Fiber) is a kind of the carbon nanotube (CNT) and has highly thermal conductivity and strength. The composites are fabricated by spark plasma sintering (SPS). The stress-strain curves of the composites are obtained by pure tensile tests and show that the composites have brittle behavior. A numerical simulation based on the micromechanics is conducted to estimate nonlinear behavior in the elastic and plastic deformation of the stress-strain relations of the composites. Both Eshelby and Mori-Tanaka theories, Weibull function, and Ramberg-Osgood law are used for the numerical simulation. As a result, it is found that the stress-strain relations of the composites are well simulated by Mori-Tanaka theory, and that the numerical simulations shows the developments of the damage in the matrix with increase in the volume fraction of VGCF. - HONDA Shinya, NARITA Yoshihiro, SASAKI KatsuhikoJournal of System Design and Dynamics 3 6 867 - 876 The Japan Society of Mechanical Engineers 2009年 [査読無し][通常論文]

A new design method is proposed here to maximize the fundamental frequency of laminated composite plates reinforced by curvilinear fibers. Spline functions represent arbitrarily shaped fibers and the Ritz method generates frequency equations. The optimum curvilinear shapes are searched for the maximum fundamental frequencies using a genetic algorithm, and increments of data points which define the spline shape are used as design variables under the limited range of undulation. Comparison of the present analysis method gives good agreement with the finite element method in terms of natural frequencies and vibration modes, and the optimized results show that the present plate with optimally shaped curvilinear fibers gives higher or equal fundamental frequencies than those of conventional plates with optimally oriented parallel fibers. - Tsuyoshi Mayama, Katsuhiko Sasaki, Mitsutoshi KurodaACTA MATERIALIA 56 12 2735 - 2743 2008年07月 [査読有り][通常論文]

This study is a quantitative evaluation of dislocation structures due to cyclic plasticity with small strain amplitudes in austenitic stainless steel 316L. First, dislocation structures in specimens after 100 cycles of cyclic loading with strain amplitudes of 0.251%, 0.75% and 1.0% were observed by transmission electron microscopy (TEM). The observations showed that cyclic loading with larger strain amplitudes results in the organization of more uniform dislocation cell structures. Secondly, an image analysis method for evaluation of the TEM images is proposed. The proposed method quantitatively evaluates the strain amplitude dependency of the organization of dislocation structures. Finally, the accumulation of shear slips on slip systems during cyclic loading is estimated by using crystal plasticity finite element analysis. The distribution of the accumulated shear slips correlates with the organization of dislocation structures. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. - 今西 輝光, 佐々木 克彦, 片桐 一彰, 垣辻 篤日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A 74 741 655 - 661 一般社団法人日本機械学会 2008年05月25日 [査読有り][通常論文]

Composite materials are made of vapor-grown carbon fibers (VGCF) with aluminum based matrices. Two aluminum based matrices such as pure aluminum matrix and matrix added Al-12 Si to pure aluminum are chosen for the composite materials. The thermal conductivities of the composite materials were measured by the method of laser flash, and mechanical properties such as tensile strength and total elongation are measured by pure tensile tests. The test results show that the matrix added-Al-12 Si to the pure aluminum is benefit to increase the thermal conductivity of the composite materials of VGCF. The thermal conductivity of the composite material with the uniform alignment of VGCF is higher than that with the random alignment of the VGCF. However, the tensile strength of the composite of VGCF decreases in both case of the random alignment and the uniform alignment. - Feng Jua, Zihui Xia, Katsuhiko SasakiJOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS 1 1 86 - 95 2008年01月 [査読有り][通常論文]

Finite element method (FEM) has been extensively applied in the analyses of mechanical and biomechanical properties of stents. Geometrically, a closed-cell stent is an assembly of a number of repeated unit cells and exhibits periodicity in both longitudinal and circumferential directions. The objective of this paper is to study the FEM models for the analysis of stents. To this end, three models, termed respectively as the Panel, RUC (repeated unit cell) and RUC, (repeated unit cell with a free end) models, are proposed incorporating rotationally symmetrical, periodic and free edge conditions. The proposed models are applied to the analysis of stents of Palmaz-Schatz and sinusoidal types. The Panel model reduces the size of the numerical model from the full, half or quarter stent to a strip of it without losing the computational accuracy. The RUC model gives satisfactory results for the inner part of the stent except for the two ends. The RUC model, described here for the first time, provides accurate results for both the inner part and the distal ends of the stent. in addition, it allows the prediction of the well-known phenomenon of "dog-boning", in which the balloon is excessively expanded at the two ends of the stent. (c) 2007 Elsevier Ltd. All rights reserved. **シリンダーヘッド用アルミ合金の微視的組織変化と材料挙動**高橋 剛, 佐々木克彦, 飯田真, 豊田武司日本機械学会論文集A編 30 1 113 - 120 2008年 [査読有り][通常論文]- HONDA Shinya, OONISHI Yoshimasa, NARITA Yoshihiro, SASAKI KatsuhikoJournal of System Design and Dynamics 2 1 76 - 86 The Japan Society of Mechanical Engineers 2008年 [査読有り][通常論文]

In the past few decades, composite materials composed of straight fibers and polymer matrix have gained their status as the most promising material for light-weight structures. Technical merit of the composites as tailored material also provided practical advantages in the optimum design process. Recently, it is reported that the fabrication machine has been developed to make curved fibers embedded in the matrix material. Based on such technical advancement, this paper proposes an analytical method to study vibration of composite rectangular plates reinforced along curved lines. The approach is based on the Ritz method where variable fiber direction can be accommodated. For this purpose, the fibers continuously changing their direction are formulated as the variable bending stiffness in the total potential energy. A frequency equation is derived by the Ritz minimizing process, and frequency parameters are calculated as the eigenvlaues in the eigenvalue problem. In numerical results, the accuracy of the method is presented by comparing present results with FEM results. The advantages of present plate are confirmed by comparing natural frequencies and mode shapes with those of conventional composite and isotropic plates, and the effectiveness of the new solution to the most recent problem is demonstrated. - 大口 健一, 佐々木 克彦, 麻生 節夫年次大会講演論文集 2008 199 - 200 一般社団法人日本機械学会 2008年Solder joints in electronic package must employ lead-free solder alloys for environmental concerns. Since the solder joints are often subjected to cyclic loadings, the lead-free solder alloys must have enough fatigue strength. Therefore, the fatigue characteristics of the lead-free solder alloys must be investigated by conducting fatigue tests. Especially, the tests should be conducted considering the strain rate effect on the fatigue life because the deformation of solder alloys always shows remarkable time dependency due to creep deformation under ordinary circumstances. In this study, the fatigue tests using Sn-3.0Ag-0.5Cu lead-free solder were conducted by the cyclic tension-compression loadings whose strain rates were different in each loading direction. The creep strains in the hysteresis loop caused by the cyclic loading were estimated by conducting the cyclic stepped ramp loading test. Also the relationship between the estimated creep strain and the fatigue life was discussed.
- Kohei Fukuchi, Yoshinori Kin, Katsuhiko Sasaki, Terumitsu Imanishi, Kazuaki Katagiri, Atsushi Kakitsuji, Yoshihiro NaritaProgress of Composites 2008 in Asia and Australasia - Proceedings of the 6th Asian-Australasian Conference on Composite Materials, ACCM 2008 60 - 63 2008年 [査読有り][通常論文]

In this paper, the evaluation of the strength of the VGCF/Aluminum composites which have highly thermal conductivity is reported. The composites are made by spark plasma sintering (SPS). The stress-strain curves of the composites are obtained by the tensile tests and show that the composites have brittle behavior. The brittleness of the composites becomes higher with increase in the volume fraction of VGCF. A numerical simulation based on the micromechanics is conducted to estimate nonlinearities of the stress-strain relations of the composites. The theories of Eshelby, Mori-Tanaka, and Weibull are used for the numerical simulation. The stress-strain relations of the composites are well simulated by these theories. - Terumitsu Imanishi, Katsuhiko Sasaki, Kazuaki Katagiri, Atsushi KakitsujiProgress of Composites 2008 in Asia and Australasia - Proceedings of the 6th Asian-Australasian Conference on Composite Materials, ACCM 2008 76 - 79 2008年 [査読有り][通常論文]

The purpose of this paper is to fabricate composites of which the matrix is aluminum, with a high thermal conductive characteristic. It is well known that carbon nanotubes (CNT) and Vapor-Grown Carbon Fiber (VGCF) have a very high thermal conductivity. The composites having the high thermal conductivity were fabricated with the VGCF filler and the aluminum matrix by spark plasma sintering. To improve the thermal conductivity of the composites, small amount of CNT were added to the VGCF filler. The effect of the addition of CNT on the thermal conductivity was examined by both the finite element analysis (FEM) and the measurements of the thermal conductivity. Both the FEM analysis and the measurements of the thermal conductivity showed that the thermal conductivity of the composites added CNT is 8-25 % higher than that of composites without the CNT addition. The FEM analysis and FE-SEM observation show that the higher thermal conductivity due to the CNT addition comes from the VGCF-CNT-VGCF cross-links. - 浅野 佑介, 今西 輝光, 佐々木 克彦, 片桐 一彰, 垣辻 篤, 成田 吉弘年次大会講演論文集 2008 0 277 - 278 一般社団法人 日本機械学会 2008年 [査読有り][通常論文]

Vapor-grown carbon fiver (VGCF)/Aluminum composites, which have high thermal conductivity, are fabricated in this paper. The thermal conductivity of the composites is about 2.5 times higher than that of the pure aluminum of the matrix if the direction of VGCF is aligned. To improve the thermal conductivity of the composite materials, small amount of CNTs are added to the composite materials. The composite materials added CNTs have about 20% higher thermal conductivity than the composite materials without CNTs. Finited Element Method (FEM) and Nan model are used to analyze the effect of the CNT addition. The increase rate of thermal conductivity due to the CNTs addition is analyzed well by the FEM analysis. Thermal conductivity is also calculated by Nan model using the results obtained by the FEM analysis. **A General Finite Element Analysis Method for Balloon Expandable Stents based on Repeated Unit Cell (RUC) Model**Zihui Xia, Feng Jua, Katsuhiko SasakiJournal of Finite Elements in Analysis and Design 1 86 - 95 2008年 [査読有り][通常論文]- Zihui Xia, Feng Ju, Katsuhiko SasakiFINITE ELEMENTS IN ANALYSIS AND DESIGN 43 8 649 - 658 2007年05月 [査読有り][通常論文]

A successful deployment of the stent is dependent on the good understanding of its mechanical properties. This paper presents a general RUC (repeated unit cell) approach for the analysis of balloon expandable stents with various types of closed cells. The application of the unified periodic boundary conditions on the RUC model of the stent is formulated. Numerical analysis is performed by the ABAQUS FEM package. Stents of the Palmaz-Schatz type and NIR (R) type with V- or S-shaped links are analyzed with the RUC models and the numerical results agree well with those obtained by much larger models in available publications. The global deformation pattern and the stress distribution of the entire stent can also be obtained by a geometrical tessellation or assembling of the deformed RUCs. It is found from the numerical analysis that the diameter of the stent during deployment changes slowly at the start and increases drastically when the internal pressure reaches a critical value where yielding hinges are formed. V- and S-stents are much easier to expand than the Palmaz-Schatz stent. However, the fore-shortenings of the V-stent and S-stent are noticeable. The advantages of the RUC approach are that the existing periodicities in the stent structure are better and directly represented by applying the periodic boundary conditions and a much smaller FEM model and less computational efforts are required to achieve the same analysis accuracy as that by larger models adopted in previous publications. (c) 2007 Elsevier B.V. All rights reserved. - Katsuhiko Sasaki, Takuji Kobayashi, Ken-ichi OhguchiJOURNAL OF ELECTRONIC PACKAGING 129 1 82 - 89 2007年03月 [査読有り][通常論文]

Time-dependent deformations such as creep and ratchetting of solder alloys are significant deformation phenomena that need to be understood to ensure the safety and reliability of solder joints in electronic pack-aging. There is much research on creep deformation of solder alloys, but ratchetting deformation, especially the correlation between creep and ratchetting deformation of solder alloys has not been investigated. This paper discusses the correlation between creep and uniaxial ratchetting deformation to establish the differences in the time-dependent deformation of lead-free and lead-containing solder alloys. Uniaxial ratchetting tests were conducted by cyclic tension-compression tests or cyclic tension-unloading tests at several ratios of the maximum to minimum stresses. Additional creep tests following the uniaxial ratchetting were also conducted to observe the effect of the uniaxial ratchetting on creep deformation. An empirical method to select an optimal lead-free solder alloy is discussed by defining a uniaxial ratchetting strain rate. The additional creep tests also show that the uniaxial ratchetting deformation has a strong correlation to the creep deformation and that the correlation is different for lead-free and lead-containing solder alloys. - Ken-ichi Ohguchi, Katsuhiko Sasaki, Setsuo AsoIPACK 2007: PROCEEDINGS OF THE ASME INTERPACK CONFERENCE 2007, VOL 2 131 107 - 113 2007年 [査読有り][通常論文]

This paper proposes a method which can estimate essential material constants of an elasto-plastic-creep constitutive model for lead-free solders by conducting only a tensile test. The test employs a stepped ramp wave loading which repeats instantaneous straining and strain maintaining. The time-independent strains can be evaluated by using the stress-strain relations at the instantaneous straining parts, while the time-dependent strain can be evaluated by using the stress-time relations during the strain maintaining parts. Based on the results of the evaluations, the material constants of the elasto-plastic-creep models are estimated. Simulations of the viscoplastic deformations of Sn-3.0Ag-0.5Cu solder alloy were also conducted to verify the validity of the proposed method. - 福地 孝平, 今西 輝光, 金 義典, 佐々木 克彦, 片桐 一彰, 仲摩 信人, 成田 吉弘北海道支部講演会講演概要集 2007 0 45 - 46 一般社団法人 日本機械学会 2007年 [査読有り][通常論文]
- 今西 輝光, 佐々木 克彦, 片桐 一彰, 佐藤 豊弘, 仲摩 信人, 清水 昭之, 垣辻 篤年次大会講演論文集 2007 0 661 - 662 一般社団法人 日本機械学会 2007年 [査読有り][通常論文]

Composite materials are made of vapor-grown carbon fibers (VGCF) with the aluminum based matrix. Two aluminum based matrix such as pure aluminum matrix and the matrix added Al-12Si to pure aluminum are chosen for the composite materials. The thermal conductivities of the composite materials were measured by the method of leaser flash, and mechanical properties such as tensile strength and total elongation are measured by pure tensile tests. The test results show that the matrix added Al-12Si to the pure aluminum is benefit to increase the thermal conductivity of the composite materials of VGCF. The thermal conductivity of the composite material with the uniform alignment VGCF is higher than that with the random alignment of the VGCF. However, the strength of the composite of VGCF decreases in the both case of the random alignment and the uniform alignment. - T. Kobayashi, K. Sasaki, K. Ohguchi, Y. NaritaKey Engineering Materials 340-341 859 - + 2007年 [査読有り][通常論文]

This paper conducts both experiments and numerical simulations of viscoplastic deformation such as creep and uniaxial ratcheting deformation of solder alloys used for electronic packaging. The correlation between creep and uniaxial ratchetting deformation is firstly discussed to establish the differences in the time-dependent deformation of lead-free and lead-containing solder alloys. Numerical simulations are also carried out using the dislocation based constitutive model [1]. Finally, the effect of the dislocation density on the viscoplastic deformation is discussed. - Tsuyoshi Mayama, Katsuhiko Sasaki, Yoshihiro NaritaPROGRESSES IN FRACTURE AND STRENGTH OF MATERIALS AND STRUCTURES, 1-4 353-358 607 - 610 2007年 [査読有り][通常論文]

The present paper investigates relationships between the macroscopic viscoplasticity and the surface morphological changes at room temperature for commercially pure titanium (CP-Ti) and austenitic stainless steel (SUS316L). Pure tensile test and tension-intermittent creep test are conducted. Both CP-Ti and SUS316L are deformed up to 16% of inelastic strain with a few unloading, and surface conditions are observed during pure tension test and tension-intermittent creep test. Qualitative surface observations and quantitative surface roughness measurements are made for the unloaded specimens. The surface roughness measurement shows that the curves plotted between surface roughness and inelastic strains are almost linear for all the present experiments. The slopes of curves depend, however, on material and type of tests, and this tendency agrees well with the qualitative surface observations by an optical microscope. The experimental results for CP-Ti suggest that different deformation mechanisms during tensile loading and creep contribute to different surface morphological changes. - Tsuyoshi Mayama, Katsuhiko Sasakib, Yoshihiro NaritaEngineering Plasticity and Its Applications from Nanoscale to Macroscale, Pts 1 and 2 340-341 871 - 876 2007年 [査読有り][通常論文]

The relationship between a phenomenological constitutive model and dislocation structures is investigated for type 316L stainless steel in cyclic plasticity. First, the cyclic plastic loading tests are conducted to observe the macroscopic deformation of the stainless steel under constant small strain amplitudes at room temperature, and it is found that different cyclic hardening and softening behaviors exist depending on the strain amplitudes. Secondly, from the microscopic viewpoint, qualitative observation is made to clarify the physical mechanism of the cyclic hardening and softening behaviors by using a transmission electron microscope (TEM). The degree of heterogeneous deformation is estimated by high and low magnification observations in the dislocation structures. These results reveal that the dislocation structures obtained after the sufficiently large number of cyclic loading are almost similar overall, even though the observed grains have different crystal orientations. This fact suggests that there are possibilities to incorporate the evolution of dislocation structure into macroscopic models. Finally a macroscopic constitutive model is proposed by considering the change of the dislocation structures due to the cyclic loading. - Tsuyoshi Mayama, Katsuhiko Sasaki, Yoshihiro NaritaMECHANICAL BEHAVIOR OF MATERIALS X, PTS 1AND 2 345-346 49 - + 2007年 [査読有り][通常論文]

In the present study, a new approach is conducted to evaluate dislocation structure induced by cyclic plasticity. First, cyclic plastic loading tests are carried out up to 100 cycles with three different small strain amplitudes on SUS316L stainless steel at room temperature. The test result presents the dependence of the strain amplitude on cyclic hardening and softening behaviors. Specifically, it is found that the cyclic loading test with strain amplitude of 0.25% shows both cyclic hardening and cyclic softening, while the cyclic loading tests with strain amplitudes of 0.75% and 1.0% show no cyclic softening. Secondly, the dislocation structures of the specimens after cyclic loading are observed by using a transmission electron microscope (TEM), and this observation reveals that the dislocation structure after cyclic loading test depends on the strain amplitude. Finally, a quantitative evaluation method of the dislocation structure is also proposed. The TEM images are converted into binary images and the resolution dependence of the generated binary image is used to visualize the characteristics of the dislocation structure. The relationship between strain amplitudes of cyclic plasticity and dislocation structure organization is clarified by the evaluation method. Finally, the heterogeneity of the dislocation structure is discussed. - T. Kobayashi, K. Sasaki, K. Ohguchi, Y. NaritaMECHANICAL BEHAVIOR OF MATERIALS X, PTS 1AND 2 345-346 97 - + 2007年 [査読有り][通常論文]

This paper discusses ratchetting deformation of lead-free solder Sn/3Ag/0.5Cu and lead-containing solder alloy Sn/37Pb with several stress amplitudes and stress ratios of the maximum stress to the minimum stress. First the uniaxial ratchetting tests are conducted with three maximum stresses and five stress ratios. The all tests are conducted using cylindrical bulk specimens of the solder alloys at 313 K. The test results show that there is the difference in the viscoplastic deformation behavior between two solder alloys. The relationship between ratchetting strain and time is estimated by Biley-Norton law to explain that the uniaxial ratchetting deformation is strongly dominated by the viscous deformation. Finally, the ratchetting deformation is simulated by the dislocation based constitutive model proposed by Estrin [1]. The simulations show that there is a possibility to simulate the uniaxial ratchetting by clarifying the dislocation mechanism of the solder alloys. - Katsuhiko Sasak, Terumitsu Imanishi, Kazuaki Katagiri, Atushi Kakitsuji, Toyohiro Satoh, Akiyuki Shimuza, Nobuhito NakamaPROGRESSES IN FRACTURE AND STRENGTH OF MATERIALS AND STRUCTURES, 1-4 353-358 587 - 590 2007年 [査読有り][通常論文]

In this paper, carbon nanotube (CNT) containing aluminum composite materials, which have good thermal conductivity, are made by the plasma activated sintering. CNT and vapor-grown carbon fiver (VGCF) as a super multi-wall CNT are used for the composite materials. To clarify the deformation and thermal characteristic of the composite materials, Young's modulus and thermal conductivity are measured. Finally, the micromechanical discussion is also conducted using Mori-Tanaka model. - Takuma Kawakami, Yoshihiro Narita, Katsuhiko SasakiADVANCES IN COMPOSITE MATERIALS AND STRUCTURES, PTS 1 AND 2 334-335 93 - + 2007年 [査読有り][通常論文]

Composite materials are frequently used in automobile and other moving vehicle structures. External and internal sounds sometimes cause unpleasant effects on the users and environment, and reduction of such sound is one of the key engineering problems. This study presents an acoustic radiation analysis from forced vibration of laminated rectangular plates and proposes a design approach to reduce the sound pressure from the plates. In the analysis the sound pressure at an arbitrary point over the plate is derived and is used as an object function in the optimization. A set of the fiber orientation angles is used as the design variable, and is optimized to minimize the sound pressure at the designated point. It is shown in numerical examples that the optimum design for sound pressure reduction is possible by the present approach. - Kenichi Murayama, Yoshihiro Narita, Katsuhiko SasakiADVANCES IN COMPOSITE MATERIALS AND STRUCTURES, PTS 1 AND 2 334-335 97 - + 2007年 [査読有り][通常論文]

The effect of plate thickness is studied on the optimum lay-ups of laminated rectangular plates by considering the first-order shear deformation through the thickness. An analytical method is presented to calculate the natural frequencies and mode shapes of the relatively thick plates. Boundary conditions at the plate edges are given by arbitrary sets of free, simply supported and clamped edges. The layerwise optimization (LO) approach is used as an optimization tool to make the fundamental frequencies maximized. Numerical results are successfully presented to clarify the thickness shear effect on the optimum lay-ups of the laminated plates. In general, it is shown that the thickness shear effect causes relatively small changes in the optimum lay-ups while it reduces the natural frequency to a large extent. - T. Mayama, K. Sasaki, H. IshikawaINTERNATIONAL JOURNAL OF PLASTICITY 23 5 915 - 930 2007年 [査読無し][通常論文]

This paper presents a unified constitutive model for cyclic viscoplasticity and changes occurring in subsequent viscoplastic deformation due to the evolution of dislocation structures. The model considers the viscoplastic potential and a modified Rambcrg-Osgood law. Stress is assumed to divide into three components: back stress (the center of the yield surface), flow stress (the radius of the yield surface), and viscous stress (overstress). The modification of the Ramberg-Osgood law is carried out employing memorized back stress. The applicability of the model to monotonic loading, pure creep, tension-compression cyclic loading, subsequent creep, and subsequent stress-relaxation were verified by comparing the predictions with experiments of Type 316L stainless steel at room temperature. The relationships between the internal variables in the model and the dislocation structures organized by cyclic deformations are also discussed. (c) 2006 Elsevier Ltd. All rights reserved. - Takuma Kawakami, Yoshihiro Narita, Katsuhiko SasakiKey Engineering Materials 334-335 89 - + 2007年 [査読有り][通常論文]

Structural plate elements in composite structures are typically fabricated by stacking orthotropic layers, each of which is composed of reinforcing fibers and matrix materials. In this work, three optimum design approaches are compared to clarify the advantages and disadvantages for optimizing the buckling performance of laminated composite plates. The first approach is developed recently by the authors, where the buckling load is maximized with respect to the lamination parameters by a gradient method and then the optimum lay-up design is determined by minimizing the errors between the optimum parameters and parameters for all possible discrete lay-ups. The second approach is the layerwise optimization (LO) approach where the fiber orientation angle in each layer is optimized step-by-step by repeating one dimensional search. The third one is a direct application of a simple genetic algorithm (SGA). In numerical examples, three sets of results are compared to discuss on the methodology for buckling optimization. - Shinya Honda, Yoshihiro Narita, Katsuhiko SasakiADVANCES IN COMPOSITE MATERIALS AND STRUCTURES, PTS 1 AND 2 334-335 89 - + 2007年 [査読有り][通常論文]

Structural plate elements in composite structures are typically fabricated by stacking orthotropic layers, each of which is composed of reinforcing fibers and matrix materials. In this work, three optimum design approaches are compared to clarify the advantages and disadvantages for optimizing the buckling performance of laminated composite plates. The first approach is developed recently by the authors, where the buckling load is maximized with respect to the lamination parameters by a gradient method and then the optimum lay-up design is determined by minimizing the errors between the optimum parameters and parameters for all possible discrete lay-ups. The second approach is the layerwise optimization (LO) approach where the fiber orientation angle in each layer is optimized step-by-step by repeating one dimensional search. The third one is a direct application of a simple genetic algorithm (SGA). In numerical examples, three sets of results are compared to discuss on the methodology for buckling optimization. - Takuji Kobayashi, Katsuhiko Sasaki, Ken-Ichi Ohguchi, Yoshihiro NaritaENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2 340-341 859 - + 2007年 [査読有り][通常論文]

This paper conducts both experiments and numerical simulations of viscoplastic deformation such as creep and uniaxial ratcheting deformation of solder alloys used for electronic packaging. The correlation between creep and uniaxial ratchetting deformation is firstly discussed to establish the differences in the time-dependent deformation of lead-free and lead-containing solder alloys. Numerical simulations are also carried out using the dislocation based constitutive model [1]. Finally, the effect of the dislocation density on the viscoplastic deformation is discussed. - K Sasaki, T TakahashiINTERNATIONAL JOURNAL OF FATIGUE 28 3 203 - 210 2006年03月 [査読無し][通常論文]

Low cycle thermal fatigue tests were conducted using an aluminum alloy AC2B-T6, which is widely used in diesel engines, especially, in cylinder heads. Specimens made of the AC2B-T6 alloy were subjected to thermal fatigue with thermo-mechanical loadings over several temperature ranges, symmetric and asymmetric strain amplitudes, and cycle periods. These test conditions are chosen considering realistic running conditions of diesel engines. A method to predict time to fatigue failure under the test conditions is proposed. The specimens were also observed by transmission electron microscope (TEM) to clarify the effects of temperature, strain amplitude, and cycle period on microstructural changes such as precipitates. Finally, the relationship between the microstructural changes and the low cycle thermal fatigue is discussed. (c) 2005 Elsevier Ltd. All rights reserved. - 眞山 剛, 佐々木 克彦, 成田 吉弘材料力学部門講演会講演論文集 2006 283 - 284 一般社団法人日本機械学会 2006年
- 眞山 剛, 佐々木 克彦, 成田 吉弘年次大会講演論文集 2006 485 - 486 一般社団法人日本機械学会 2006年Strain amplitude dependent cyclic plasticity of SUS316L under room temperature is investigated experimentally and theoretically. Tension-compression cyclic loading tests at a constant strain rate with three different strain amplitudes show that cyclic hardening and softening behavior depends on the strain amplitude. A modified macroscopic constitutive model describes the experimental results successfully. Dislocation structure images observed by using transmission electron microscope (TEM) are evaluated qualitatively and quantitatively. A relationship between material parameters in the model and the evolution of dislocation structure is discussed.
- 小林 琢爾, 佐々木 克彦, 成田 吉弘年次大会講演論文集 2006 733 - 734 一般社団法人日本機械学会 2006年This paper conducts both experiments and numerical simulations of viscoplastic deformation such as creep and uniaxial ratcheting deformation of solder alloys. The correlation between creep and uniaxial ratcheting deformation is firstly discussed to establish the differences in the time-dependent deformation of lead-free and lead-containing solder alloys. The experiments show that the ratcheting deformation of lead-free solder alloy is much smaller than the lead-containing solder alloy. Especially, there is much difference in the effect of the uniaxial ratcheting on the creep deformation between the two solder alloys. Then numerical simulations are also carried out using the dislocation based constitutive model. There is amoderate agreement between experiment and simulation.
- 大口 健一, 佐々木 克彦, 麻生 節夫年次大会講演論文集 2006 731 - 732 一般社団法人日本機械学会 2006年To apply the lead-free solder alloys to the electronic equipment, the strength reliability of the lead-free solder joint must be evaluated by the accurate FEM analysis. Since the deformation behavior of lead-free solder alloys shows the time dependency, the FEM analysis often employs the constitutive models of the elasto-plastic-creep type. To conduct the high-accuracy analysis by using the constitutive model, the characteristics of the elastic, plastic and creep deformations of lead-free solder alloys should be evaluated accurately. Moreover, the evaluation should be conducted immediately because taking a long time for the evaluation delays the practical use of the lead-free solder alloys in the electronic equipment. In this study, we propose a method which can evaluate the characteristics of the elastic, plastic and creep deformations of lead-free solder alloys by conducting only one 1 test. The test was conducted under the stepped ramp wave loading which consists of the instantaneous straining parts and maintaining strain parts using Sn-3.OAg-0.5Cu lead-free solder alloys. The stress-strain relations at the instantaneous straining parts in the test are used for evaluating the elasto-plastic deformation, while the stress-time relations during the maintaining strain parts are used for evaluating the creep deformation.
- 金 義典, 仲摩 信人, 佐々木 克彦, 今西 輝光, 戸田 康隆, 成田 吉弘, 片桐 一彰, 佐藤 豊弘, 清水 昭之, 垣辻 篤北海道支部講演会講演概要集 2006 0 97 - 98 一般社団法人 日本機械学会 2006年 [査読有り][通常論文]
- 佐々木 克彦, 今西 輝光, 片桐 一彰, 佐藤 豊弘, 清水 昭之, 垣辻 篤, 仲摩 信人材料力学部門講演会講演論文集 2006 0 261 - 262 一般社団法人 日本機械学会 2006年 [査読有り][通常論文]
- KI Ohguchi, K Sasaki, M IshibashiJOURNAL OF ELECTRONIC MATERIALS 35 1 132 - 139 2006年01月 [査読無し][通常論文]

A method to separate plasticity and creep is discussed for a quantitative evaluation of the plastic, transient creep, and steady-state creep deformations of solder alloys. The method of separation employs an elasto-plastic-creep constitutive model comprised of the sum of the plastic, transient creep, and steady-state creep deformations. The plastic deformation is expressed by the Ramberg-Osgood law, the steady-state creep deformation by Garofalo's creep law, and the transient creep deformation by a model proposed here. A method to estimate the material constants in the elasto-plastic-creep constitutive model is also proposed. The method of separation of the various deformations is applied to the deformation of the lead-free solder alloy Sn/3Ag/0.5Cu and the lead-containing solder alloy Sn/37Pb to compare the differences in the plastic, transient creep, and steady-state creep deformations. The method of separation provides a powerful tool to select the optimum lead-free solder alloys for solder joints of electronic devices. - T Mayama, K SasakiINTERNATIONAL JOURNAL OF PLASTICITY 22 2 374 - 390 2006年 [査読無し][通常論文]

This paper investigates the effects of cyclic preloading on the subsequent viscoplastic deformation. A series of experiments such as the subsequent creep, subsequent stress relaxation, and cyclic loading with strain rate changes after cyclic preloading were conducted with Type 304 stainless steel at room temperature. The cyclic proportional and non-proportional loadings were conducted as cyclic preloadings. Tension-compression loading was chosen as the cyclic proportional loading, and circular and cruciform loading as the cyclic non-proportional loading. The experimental results showed that the subsequent deformation changes with the number of cycles of cyclic preloading. The differences in the subsequent deformation were examined by transmission electron microscopy (TEM). The observations suggest that changes in the dislocation structure depending on the number of cycles of cyclic preloading affect the subsequent viscoplastic deformation. (c) 2005 Elsevier Ltd. All rights reserved. - 眞山 剛, 中田 光洋, 佐々木 克彦, 石川 博將材料力学部門講演会講演論文集 2005 387 - 388 一般社団法人日本機械学会 2005年The evolution of dislocation structures during cyclic plastic loadings is investigated. The loading paths of cyclic plastic loadings conducted in this study are tension-compression, torsion, cruciform, and circular loading under constant strain amplitudes. The dislocation structures of the specimens after the cyclic loadings are observed by Transmission Electron Microscope (TEM). The meso-structures, the dislocation structures of five neighbourhood grains, are also observed to verify the inhomogeneity of deformation of polycrystalline metals. Finally the relationships between cyclic plastic loadings and the evolution of dislocation structures are discussed.
- 本田 真也, 成田 吉弘, 佐々木 克彦材料力学部門講演会講演論文集 2005 619 - 620 一般社団法人日本機械学会 2005年Fiber Reinforced Plastics (FRP) has been utilized in applications of automobile and aircraft structures because of the high specific strength and stiffness ratios. These FRP composites are typically fabricated by stacking orthotropic laminas, each composed of reinforcing fibers and matrix materials. In this work, an optimum design approach is presented by using the lamination parameters with the gradient method, and is used to optimize buckling behaviors of laminated composite plates. This approach can derive the optimum lay-up design from the calculated values of the parameters, and yields the maximum buckling loads with corresponding optimum lay-ups (fiber orientation angles).
- 小林 琢爾, 佐々木 克彦, 大口 健一, 成田 吉弘年次大会講演論文集 2005 483 - 484 一般社団法人日本機械学会 2005年Ratchetting deformations of solder alloys are significant deformations for the safety and reliability of solder joints of electronic packaging. This paper discusses a correlation between creep and uniaxial ratchetting deformations to clarify the difference in the time-dependent deformations between lead-free and lead-containing solder alloys. Uniaxial ratchetting tests are conducted by cyclic tension-compression and cyclic tension-unloading with the several ratios of maximum to minimum stresses. Additional creep tests are also conducted after the uniaxial ratchetting tests to clarify the effect of the uniaxial ratchetting on the creep deformation. A method to evaluate the uniaxial ratchetting deformation is discussed using the creep curves. The results show that the uniaxial ratchetting deformation correlates to the creep deformation and that the correlation is different between the lead-free and lead-containing solder alloys.
- 眞山 剛, 佐々木 克彦, 成田 吉弘年次大会講演論文集 2005 485 - 486 一般社団法人日本機械学会 2005年A relationship between viscoplastic deformation and dislocation structures is investigated to develope a meso-structure based constitutive model. Experiments conducted in this study are tension-compression cyclic loading and the subsequent stress relaxation tests. The subsequent stress relaxation tests show the dependency of the number of cyclic preloading. Transmission electron microscope observations of specimens after cyclic loading are also conducted. Finally a viscoplastic constitutive model and meso-structural change of material are correlated based on the theoritical calculations.
- 戸田 康隆, 佐々木 克彦, 成田 吉弘, 片桐 一彰, 佐藤 豊弘, 今西 輝光, 仲摩 信人, 垣辻 篤年次大会講演論文集 2005 0 411 - 412 一般社団法人 日本機械学会 2005年 [査読有り][通常論文]

Since carbon nanotubes (CNT) have huge strength, thermal conductivity, and electric conductivity CNT is expected to be used for macroscopic materials. This paper conducted pure tensile tests of CNT-containing aluminum materials to develop a new CNT-containing composite material for thermal converters, which has high thermal conductivity and almost same strength as a pure aluminum. Difficulties to develop the CNT-containing composite material are to control conditions of boundary surfaces between CNT and aluminum. The control is an important factor for the properties of thermal conductivity. To improve the condition of the boundary surfaces the composite materials were subjected to cold rolling. The effects of the rolling on Young's modulus and the ultimate strength were investigated. The total elongation was also investigated because the ductility of the CNT-containing composite materials is important to apply the composite materials to the thermal converters. - Ken-ichi Ohguchi, Katsuhiko SasakiAdvances in Electronic Packaging 2005, Pts A-C 1791 - 1796 2005年 [査読有り][通常論文]

A viscoplastic constitutive model for lead-free solder alloys was proposed. The proposed model is the elasto-plastic-creep type which comprises the sum of the plastic, transient creep, and steady-state creep strains. To determine the material constants employed by the proposed constitutive model, a simple method to estimate the constants was also proposed. The method was applied to the lead-free solder alloy of Sn-3.0Ag-0.5Cu. Then, all the material constants for Sn-3.0Ag-0.5Cu employed by the constitutive model were estimated only by three tensile tests and one subsequent stress relaxation test. Using the constitutive model with the estimated constants, the ratcheting deformations of Sn-3.0Ag-0.5Cu under different strain rates were simulated. As a result, the simulations could predict the strain rate effect on the ratcheting deformation well. Therefore, the FEM analysis employing the constitutive model with the estimation method for material constants must be useful for the faster selection of the optimum lead-free solder alloys for electronic devices mounting because the material constants in the model can be estimated without conducting the long-time creep tests. - Katsuhiko Sasaki, Takuji Kobayashi, Ken-ichi OhguchiAdvances in Electronic Packaging 2005, Pts A-C 1773 - 1778 2005年 [査読有り][通常論文]

Ratchetting deformations of solder alloys are significant deformations for the safety and reliability of solder joints of electronic packaging. This paper discusses a correlation between creep and uniaxial ratchetting deformations to clarify the difference in the time-dependent deformations between lead-free and lead-containing solder alloys. Uniaxial ratchetting tests are conducted by cyclic tension-compression and cyclic tension-unloading with the several ratios of maximum to minimum stresses. Additional creep tests are also conducted after the uniaxial ratchetting tests to clarify the effect of the uniaxial ratchetting on the creep deformation. A method to evaluate the uniaxial ratchetting deformation is discussed using the creep curves. The results show that the uniaxial ratchetting deformation correlates to the creep deformation and that the correlation is different between the lead-free and lead-containing solder alloys. - T Mayama, K Sasaki, H IshikawaPROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE 218 9 901 - 908 2004年09月 [査読有り][通常論文]

This paper treats both experiments and simulations of biaxial ratcheting. The experiments are conducted using a tubular specimen of type 304 stainless steel at room temperature. The specimen was subjected to cyclic shear straining under the axial superposed stress. The experiments show that the biaxial ratcheting strain was affected by the cyclic shear strain amplitude, the shear strain rate and the superposed stress level. Larger biaxial ratcheting strain occurred in the case of tensile superposed stress compared with that in the case of the compressive superposed stress. Moreover, even under the zero superposed stress, biaxial ratcheting strain occurred in the axial direction due to the cyclic shearing, straining. Finally, the biaxial ratcheting behaviours were simulated by the unified constitutive model proposed by the authors. The characteristic features of the biaxial ratcheting behaviour, especially the axial strain due to the cyclic shear straining superposed on the zero axial stress, are well simulated by the constitutive model. - K Ohguchi, K Sasaki, M Ishibashi, T HoshinoJSME INTERNATIONAL JOURNAL SERIES A-SOLID MECHANICS AND MATERIAL ENGINEERING 47 3 371 - 379 2004年07月 [査読有り][通常論文]

This paper applies a constitutive model proposed previously by the authors to three lead-free solder alloys of Sn/Ag, Sn/Bi and Sn/Zn. First, the material constants in the constitutive model are determined using the so-called "Plasticity-creep separation method" by simple tests such as pure tensile tests. The constitutive model is incorporated into a general purpose Finite Element Method program ANSYS using the stress integration method. The material constants for the lead-free solders could be simply determined using only the data obtained by the pure tensile tests with three strain rates. The basic mechanical deformation such as creep and cyclic deformation are simulated by the constitutive model using the material constants determined using the "plasticity-creep separation method". Thermal deformation during a reflow process with electronic packaging is also simulated by the constitutive model. - T Takahashi, Y Sugimura, K SasakiJOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME 126 1 25 - 32 2004年02月 [査読有り][通常論文]

Depending on casting methods, aluminum alloy cylinder heads differ greatly in quality and local strength as well as overall strength. Obviously, casting methods largely effect the durability of a cylinder head. Therefore, in order to precisely evaluate the durability of a newly-designed cylinder head by CAE, it is necessary to introduce a new method with the effects of a casting method taken into account. In our research, a method has been devised to be used in CAE in such processes from engineering to manufacturing for evaluation. More specifically, by using the method, metallurgical microstructure of cast aluminum alloy is analyzed by dividing cylinder head into such domains as lower deck, middle and upper deck parts for mechanical properties and a casting defect of porosity. The domain profile information on mechanical properties and porosity has helped us improve accuracy in the structural analysis. - 中田 光洋, 佐々木 克彦, 眞山 剛年次大会講演論文集 2004 301 - 302 一般社団法人日本機械学会 2004年In this paper, a series of tests are conducted to clarify viscoplastic deformation of Ti-6Al-4V Pure tensile tests with several strain rates, creep tests, stress relaxation tests and uniaxial ratchetting tests are chosen for the purpose. Moreover, cyclic tension-compression loading is also performed. The test results show that Ti-6Al-4V has viscoplastic deformation, and large creep, stress relaxation and ratchetting strain occur in spite of the small stress rate effect of the pure tension. Particularly, the large creep strain and ratchetting strain occur though the stress levels for creep tests and maximum stresses for ratchetting tests are lower than the yield stress.
- 眞山 剛, 佐々木 克彦, 中田 光洋年次大会講演論文集 2004 299 - 300 一般社団法人日本機械学会 2004年Commercially pure (CP) titanium is widely used for biomaterials because of its good biocompatibility. Actually used biomaterials for a stent, for example, are subjected to inelastic deformation. However the inelastic deformation of CP titanium has not been clarified yet. In this paper, inelastic deformation, especially, viscoplastic deformation such as strain rate effect, creep, stress relaxation and uniaxial ratchetting are investigated by a series of tests using CP titanium at room temperature. Microscopic observation is also conducted by uniaxial loading tests using a rectangular specimen. The test results show that the CP titanium has large viscoplastic deformation, and especially large creep deformation and stress relaxation cause a problem to use CP titanium for a biomaterial.
- 眞山 剛, 佐々木 克彦材料力学部門講演会講演論文集 2004 423 - 424 一般社団法人日本機械学会 2004年
- 佐々木 克彦, 大口 健一材料力学部門講演会講演論文集 2004 257 - 258 一般社団法人日本機械学会 2004年
- 大口 健一, 佐々木 克彦, 石橋 正博材料力学部門講演会講演論文集 2004 255 - 256 一般社団法人日本機械学会 2004年
- T Mayama, K Sasaki, H IshikawaADVANCES IN ENGINEERING PLASTICITY AND ITS APPLICATIONS, PTS 1 AND 2 274-276 229 - 234 2004年 [査読有り][通常論文]

In this study, subsequent time-dependent deformation after cyclic preloading and a constitutive model is discussed. Stress-strain curves of 10(th) and 3(th) cycle of cyclic loading under the strain rate of 0.01 %/sec with the strain amplitude of 0.5 % using Type 304 stainless steel at room temperature are almost same. However, creep and stress relaxation after the two cyclic loading are different due to the number of cycle of the cyclic preloading. The experimental results are simulated by a unified constitutive model. The model is constructed referring to dislocation observations after 10(th) and 30(th) cycles of cyclic loading by using TEM (Transmission Electron Microscope). The constitutive model shows good agreements with the experimental results of the subsequent creep and the subsequent stress relaxation. - 柳本 陽征, 佐々木 克彦, 石川 博將日本機械学会論文集（Ａ編） 70 689 147 - 154 一般社団法人日本機械学会 2004年 [査読無し][通常論文]

In this paper, experimental and theoretical researches on the viscoplasticity of lead and lead-free solder alloys are conducted. First, experiments such as tension-compression loading with several stress amplitudes and strain rates, creep tests at several stress levels, and stress relaxation tests are conducted using specimens made of Sn-37 Pb as the lead solder alloys and Sn-3 Ag-0.5 Cu as the lead-free solder alloys at several temperatures. The test results show that the lead-free solder alloy has smaller strain rate effects, creep strain and stress relaxation than those of the lead solder alloy. The viscoplastic deformations of both lead and lead-free solder alloys are simulated by a viscoplastic constitutive model. The simulations show that the constitutive model can successfully apply to the pure sension, the cyclic loading, the creep deformation and the stress relaxation of both the lead and the lead-free solder alloys. FEM analysis of the bend of the substrate is also conducted by MSC. Marc, in which the constitutive model for viscoplasticity is incorporated. As a result, it is found that the bend of substrate using the lead-free solder joints has much larger bend than that using the lead solder joints. - K Ohguchi, K SasakiJSME INTERNATIONAL JOURNAL SERIES A-SOLID MECHANICS AND MATERIAL ENGINEERING 46 4 559 - 566 2003年10月 [査読有り][通常論文]

This paper describes a constitutive model for solder alloys and a method to determine the material parameters of the model. First, a constitutive model that divides the inelastic deformation into plastic and creep parts is proposed. Next, a numerical method for the determination of the material parameters used in the model is developed. In this method, the material parameters for the creep part are determined first by pure tensile tests at different strain rates, and the creep strain is calculated next. Subtracting the calculated creep strain from the pure tensile deformation, the stress-strain relation for the time independent strain is obtained. Then, the material parameters for the time independent strain, such as the elastic and plastic strain, are simply determined from the obtained stress-strain relations. Simulations of the stress relaxation after several different preloadings were carried out to verify the accuracy of the proposed model and numerical method. - 佐々木 克彦, 高橋 剛材料力学部門講演会講演論文集 2003 415 - 416 一般社団法人日本機械学会 2003年In this paper, micro and macroscopic observations on the thermomechanical deformation of the aluminum alloys AC2B-T6 used for cylinder heads of automobile engines are conducted to clarify the effects of the precipitates on the thermomechanical deformation and fatigue failure. The thermomechanical loading is out-of-phase triangle waves which are a minimum mechanical strain at the highest temperature and a maximum mechanical strain at the lowest temperature. The precipitates during the thermomechanical deformation are observed by TEM. The correlations of the density of the precipitates with the stress-strain relations and fatigue failure are discussed from the microscopic point of view.
- 佐々木 克彦, 柳本 陽征, 石川 博將年次大会講演論文集 2003 235 - 236 一般社団法人日本機械学会 2003年Deformations of the solder alloys used for solder joints due to cyclic thermal condition is governed by ratchetting deformation. Then simulations of the ratchetting deformation are required for the accurate reliability design of lead-free board level packaging. This paper performed experimental studies of the mechanical ratchetting deformation of lead-free solder alloys. Since the mechanical ratchetting is dominated by viscosity of materials, additional creep tests after the mechanical ratchetting deformation is also discussed. The interaction between mechanical ratchetting and creep deformation is clarified from the difference of the additional creep deformation due to the number of cycles of the primary mechanical ratchetting. Sn-3Ag-0.5Cu is chosen for the lead-free solder alloy, while Sn-37Pb for the lead solder alloy.
- T Mayama, K Sasaki, H IshikawaENGINEERING PLASTICITY FROM MACROSCALE TO NANOSCALE PTS 1 AND 2 233-2 83 - 88 2003年 [査読有り][通常論文]

This paper treats a unified constitutive model for the viscoplastic and creep deformations. First, experimental observations on the correlation between back stress due to plasticity and creep are carried out using Type 304 stainless steel at room temperature. The experimental results show that there is the equivalence of back stress due to plastic and creep deformation. Then considering the equivalence of back stress, a unified constitutive model for plasticity and viscoplasticity is proposed. To verify the applicability of this model, the numerical simulations are conducted by the model, and compared with the experiments. - K. Sasaki, A. Yanagimoto, H. IshikawaKey Engineering Materials 233-2 779 - 784 2003年 [査読有り][通常論文]

In this paper, viscoplastic deformations of Sn-3.5Ag-0.75Cu solder alloy are discussed. First, the following experiments are conducted: (1) Pure tension at several strain rates. (2) Cyclic tension-compression loading with several strain amplitudes at several strain rates. (3) Creep tests at several stress levels. The test results show that the Sn-3.5Ag-0.75Cu solder alloy has large strain rate and temperature effects, and that there is a noticeable transient creep region in the creep curves. A viscoplastic constitutive model for the solder alloy is also discussed. The model is constructed based on the dislocation density based constitutive model proposed by Estrin [6]. The constitutive model well simulates both the time and temperature dependences on the deformation of the lead free solder alloy. Finally, the constitutive model is incorporated into a general purpose FEM program (Marc) to clarify the applicability of the model to the structural analysis. **シリンダーヘッド用アルミ合金の微視的組織および巨視的特性に及ぼす温度の影響**高橋 剛, 佐々木克彦, 永吉 隆, 熊野 正彦自動車技術会論文集 34 1 107 - 114 2003年 [査読有り][通常論文]- 高橋 剛, 佐々木 克彦, 茂泉 健, 飯田 真, 後藤 悦子『日本機械学会論文集（Ａ編）』 69 680 741 - 749 2003年 [査読無し][通常論文]
- 大口 健一, 佐々木 克彦, 野々山 裕芝, 田上 道弘『日本機械学会論文集（Ａ編）』 69 682 980 - 987 一般社団法人日本機械学会 2003年 [査読無し][通常論文]

To select the best solder alloy for the electronic packaging, a constitutive model which can be applied to alternative solder alloys is needed for the reliability evaluation such as estimations of fatigue failure using FEM analysis. In this paper, to apply the plasticity-creep separate method using the constitutive model proposed by authors to the three solder alloys such as Sn-3.5 Ag-0.75 Cu, Sn-7.5 Zn-3.0 Bi and Sn-57 Bi-1.0 Ag, the basic experiments and numerical simulations are conducted. Pure tensile tests are conducted to determine material constants of the constitutive model using the plasticity-creep separate method. The material constants determined from the only pure tensile data are used for the simulation of creep and cyclic tension-compression loading. As a result, the plasticity-creep separate method can be applied to lead-free solder alloys as well as lead solder alloys, and the simulations of the both creep and cyclic loading are successfully conducted using the material constants determined from the pure tension. - 高橋 剛, 佐々木 克彦『日本機械学会論文集（Ａ編）』 69 680 750 - 757 一般社団法人日本機械学会 2003年 [査読無し][通常論文]

The most popular aluminum alloy, AC2B-T6, was tested for thermal fatigue with the center of strain amplitude offset to take realistic engine running conditions into consideration. Test specimens were overaged to study the effects of tempering temperature on life, which turned out to be very effective for lengthening life. In the TEM microstructure observation, attention was focused on precipitates, and the average size and number of precipitates were measured. The effects of temperature, loading period strain amplitude on the characteristics of precipitates were studied to establish relation with fatigue life. As a result, it was found that the average size of a certain type of precipitates has a strong correlation with fatigue life, and was concluded that not only material properties but also microstructure should be studied to develop an aluminum alloy. - 大口 健一, 佐々木 克彦材料力学部門講演会講演論文集 2002 409 - 410 一般社団法人日本機械学会 2002年
- 眞山 剛, 佐々木 克彦, 石川 博將材料力学部門講演会講演論文集 2002 125 - 126 一般社団法人日本機械学会 2002年In this study, a series of subsequent creep tests, microscopic observations, and numerical simulations were carried out. Creep tests after cyclic loading on SUS304 stainless steel at room temperature expressed the dependence of the number of cycle of the cyclic loading. To verify this results microscopic observations were conducted by TEM, which showed that dislocation structures after cyclic loading were different even if stress-strain curves were almost same after the saturation of cyclic hardening. Finally considering dislocation density experimental results were simulated by a unified constitutive model.
- 眞山 剛, 佐々木 克彦, 石川 博將年次大会講演論文集 2002 87 - 88 一般社団法人日本機械学会 2002年In this study, a series of subsequent creep tests and microscopic observations were carried out at room temperature. Creep curves after cyclic preloading on SUS304 stainless steel had the dependence of the cycle number of the cyclic loading. Microscopic observations were also conducted by TEM to confirm the dependence of the creep curves on the cycle number. The microscopic observation showed that dislocation structures changed due to the additional cyclic loading after stress-strain relation stabilized. Finally considering dislocation density creep curves were described by Boyle-Spence type creep law.
- 大口 健一, 佐々木 克彦年次大会講演論文集 2002 431 - 432 一般社団法人日本機械学会 2002年Recently, environmental pollution caused by lead liquation from the solder in wasted electronic machines has become matter of serious concern. Therefore, a great variety of chemical compositions for the 'lead free solder' have been proposed. To use these 'lead free solder' in electronic packaging, the reliability of the solder joints by those solders to the fatigue failure has to be estimated by the FEM analysis. For the accurate analysis, a constitutive model for the lead free solder alloys has been required. The requirement is not only the precision of simulation but also the reduction of the number of experiments to determine the material parameters because the analysis has to be conducted on the proposed various composites of lead free solder joints. In this study, we show the constitutive model that can divide the inelastic deformation into the plastic and creep parts and its numerical determination method for the material constants by only pure tensile tests under several strain rates. The simulations of the creep and cyclic tension-compression loading using Sn/Ag, Sn/Zn and Sn/Bi solder alloys are conducted to verify the applicability of the model and method to the lead free solder alloys.
- Tsuyoshi Takahashi, Ken Moizumi, Makoto Iida, Katsuhiko Sasaki, Somei OhnukiSAE Technical Papers 2002年 [査読有り][通常論文]

The past efforts to develop aluminum alloy engine parts were focused on the formulation of chemical composition rather than the heat treatment conditions of aluminum alloys. Only a few studies have been made on optimizing heat treatment conditions. This paper deals with the effects of artificial aging on two aluminum alloys, A356 and A319, which have been often used for engine cylinder heads. The aluminum alloys were artificially aged under several different conditions after T6 heat treatment. The alloys were tested for such mechanical properties as pure tension, cyclic loading resistance and thermo-mechanical fatigue failure. The microstructure was observed by TEM to see the effects on microstructure in terms of mechanical properties. Copyright © 2002 Society of Automotive Engineers, Inc. - Tsuyoshi Takahashi, Takashi Nagayoshi, Masahiko Kumano, Katsuhiko SasakiSAE Technical Papers 276 - 284 2002年 [査読有り][通常論文]

Critical for the use of aluminum alloys for cylinder heads are strength and durability. In our study, the mechanism of the low cycle fatigue and creep was clarified based on the mechanical properties of aluminum alloys, such as tensile, compressive, thermal fatigue and creep characteristics, which were determined by conducting tests on test pieces. The behavior of a cylinder head under cyclic thermal condition was represented by using a high-precision analysis method with cyclic creep taken into consideration. Moreover, the high-precision analysis method turned out to be effective in estimating a low cycle fatigue life under the cyclic thermal condition. Copyright © 2002 Society of Automotive Engineers, Inc. - 佐々木 克彦, 石川 博將『日本機械学会論文集（Ａ編）』 68 665 169 - 174 一般社団法人日本機械学会 2002年 [査読無し][通常論文]

This paper treated a series of experiments and simulations concerned with biaxial ratcheting behavior. The biaxial ratchetting tests were conducted using SUS304 stainless steel subjected to cyclic torsion with superposed axial tensile or compressive stresses. Experimental results showed that (1) the axial strain occurred due to even zero superposed axial stress, and (2) biaxial ratchetting strain due to the tensile superposed stress was larger than that due to the compressive superposed stress. The biaxial ratchetting behavior was simulated by a constitutive model based on a viscoplastic potential related to dislocation density. To explain the axial strain due to zero or nonzero superposed stresses, a constitutive model was proposed, where the effect of the latent hardening on the back stress was considered in the evolution equation of the back stress. The constitutive model successfully simulated the axial strain due to zero or nonzero superposed stresses. The difference of the biaxial ratchetting strain due to the tensile and compressive superposed stresses was also well explained by the constitutive model. **エンジンシリンダヘッドの熱弾塑性クリープ解析**高橋 剛, 佐々木克彦, 永吉 隆, 辻村 明自動車技術会論文集 33 1 49 - 55 2002年 [査読有り][通常論文]- 大口 健一, 佐々木 克彦『日本機械学会論文集（Ａ編）』 68 673 1328 - 1335 2002年 [査読無し][通常論文]

For the accurate finite element analysis of solder joints in electronic packaging, a constitutive model which can describe the large time dependent deformation has been required. The requirement is not only the proposal of such a constitutive model but also the establishment of the determination method for the material parameters used in the model. In this study, we discussed on the constitutive model for solder alloys and the determination method of the material parameters for the model. First, the constitutive model that can divide the inelastic deformation into the plastic and creep parts is proposed. Next, we show the numerical method for the determination of the material parameter used in the model. In this method, the material parameters for creep part are determined firstly by pure tensile tests under several strain rates, and the creep strain is calculated. Subtracting the calculated creep strain from the pure tensile deformation, the stress-strain relation for the time independent parts is obtained. Then, the material parameters for the time independent parts such as elastic and plastic deformation are easily determined from the obtained stress-strain relations. The simulations of the stress relaxation after several different preloading are carried out to verify the applicability of the proposed model and numerical method. © 2002, The Japan Society of Mechanical Engineers. All rights reserved. - 眞山 剛, 佐々木 克彦, 石川 博將『日本機械学会論文集（Ａ編）』 68 676 1737 - 1743 一般社団法人日本機械学会 2002年 [査読無し][通常論文]

In this paper, to verify the applicability of the viscoplastic constitutive model, which was previously proposed by the authors, to the viscoplastic deformation at the high temperatures, a series of tests such as cyclic tension-compression loading with the constant strain amplitude under the constant strain rate and creep tests are carried out at the high temperatures by using oxygen-free copper (OFC). A cyclic tension-compression tests under variations of temperature is also conducted. The experimental results show that the temperature history does not affect stress-strain relations under cyclic tension-compression loading regardless of variations of temperature. Using the material constants determined by the cyclic tension-compression test at isothermal condition, creep and cyclic deformations under variations of temperature can be well simulated by the viscoplastic model. - 高橋 剛, 佐々木克彦, 熊野正彦, 通山 哲日本機械学会論文集（Ａ編） 68 668 660 - 667 一般社団法人日本機械学会 2002年 [査読有り][通常論文]

Past efforts for aluminum alloys used for engines were focused on chemical compositions rather than heat treatment conditions of the aluminum alloys. Then, there are a few studies on optimizations of the heat treatment conditions. This paper treats artificial aging effects on two aluminum alloys such as AC 4 C and AC 2 B used for cylinder heads of engines. The aluminum alloys are subjected to additional heat treatments during several time periods after T 6 heat treatments. The effects of the aging time on the mechanical behaviors such as pure tension, cyclic loading, and thermo-mechanical fatigue failure are observed by a series of tests. The microstructural observation is also carried out by TEM to clarify the effects of microstructural change of the aluminum alloys on the mechanical behaviors. - 眞山 剛, 佐々木 克彦, 石川 博將『日本機械学会論文集（Ａ編）』 68 675 1582 - 1587 一般社団法人日本機械学会 2002年 [査読無し][通常論文]

In this work, a series of biaxial ratchetting tests and numerical simulations are carried out. Experimental results obtained using the tubular specimen of SUS 304 stainless steel subjected to cyclic shear staining under the superposed axial stress show the dependence of the amount of superposed axial stress, the cyclic shear strain amplitude and the shear strain rate. Even under zero superposed stress, the ratchetting strain is induced in the axial direction. Finally, the unified constitutive model proposed by authors is used for the predictions of these biaxial ratchetting. The characteristic features of biaxial ratchetting are well described by the numerical simulation. - 高橋 剛, 佐々木克彦, 杉村 良男, 飯田 真, 峯 憲一郎日本機械学会論文集（Ａ編） 68 676 1744 - 1752 2002年 [査読有り][通常論文]
- K Sasaki, KI Ohguchi, H IshikawaJOURNAL OF ELECTRONIC PACKAGING 123 4 379 - 387 2001年12月 [査読有り][通常論文]

This study first proposes a simple constitutive model for viscoplasticity, which includes the elastic, plastic,, and creep strains independently. The plastic strain is evaluated by the flow rule employing back stresses evolved with a Ziegler Ape of hardening rule. The creep strain is evaluated by the modified Norton's law, The applicability of this constitutive model is evaluated with pure tensile tests, creep tests and cyclic tension-compression loading tests, to demonstrate the progress of viscoplastic deformation of 40Pb/60Sn solder alloys. The tests were conducted over both several temperature ranges and strain rates. As a result, it was found that the material constants used in the constitutive model could be determined by simple tests such as pure tensile and cyclic tension-compression loading tests. The simulation by the Constitutive model explains accurately the viscoplastic, deformation of the 40Pb/60Sn solder alloys. - 佐々木 克彦, 石川 博將, 柳本 陽征材料力学部門講演会講演論文集 2001 383 - 384 一般社団法人日本機械学会 2001年
- 大口 健一, 佐々木 克彦, 野々山 裕芝, 田上 道弘年次大会講演論文集 1 435 - 436 一般社団法人日本機械学会 2001年For the elastic-plastic-creep finite element analysis of solder joints in electronic devises, the determination of the material parameters used in the analysis is very difficult because the solder alloy shows the large time dependent deformation. In this study, a simple method to determine the material parameters is proposed with dividing the deformation into the time dependent and time independent parts. First, the material parameters for creep deformation are determined by pure tensile tests under several strain rates, and the creep deformation is calculated. Subtracting the calculated creep deformation from the pure tensile deformation, the stress-strain relation for the time independent parts is obtained. Then, the material parameters for the time independent parts such as elastic and plastic deformation are easily determined from the stress-strain relations removed the creep deformation.
- 真山 剛, 佐々木 克彦, 石川 博將『日本機械学会論文集（Ａ編）』 67 663 1768 - 1775 2001年 [査読無し][通常論文]

In this paper, a series of experiments, which showed the interaction between plasticity and creep, were carried out and the unified constitutive model was proposed. First, experiments such as pure tension, pure creep, cyclic loading, intermittent creep during cyclic loading and subsequent creep after cyclic loading were conducted using Type 304 stainless steel at room temperature. Then considering the equivalence of back stresses in plastic and creep deformations, the unified constitutive model was constructed and using the proposed model the experimental results were well simulated. - K Ohguchi, K SasakiJSME INTERNATIONAL JOURNAL SERIES A-SOLID MECHANICS AND MATERIAL ENGINEERING 44 1 82 - 88 2001年01月 [査読有り][通常論文]

This paper shows the temperature effect on the deformation of 60 Sn-40 Ph solder alloys and a simulation using a constitutive model for viscoplasticity. First, a series of tests, such as creep, pure tension, and cyclic tension-compression loading were conducted to clarify the temperature effect on the deformation of 60 Sn-40 Pb solder alloys. The test results showed that the deformation of the solder alloys has a large temperature dependence. Simulations of the temperature effect on the deformation were also conducted by a constitutive model previously proposed. The parameters used in the model can be determined simply from pure tension and cyclic tension-compression loading tests at several temperatures. It was also found that the constitutive model describes not only the temperature effect on the pure tension and the cyclic tension-compression loading but also the creep curves after cyclic tension-compression preloading. - 大口 健一, 佐々木 克彦, 石川 博將, 柳本 陽征材料力学部門講演会講演論文集 2000 519 - 520 一般社団法人日本機械学会 2000年
- 佐々木 克彦, 大口 健一, 柳本 陽征, 石川 博將材料力学部門講演会講演論文集 2000 517 - 518 一般社団法人日本機械学会 2000年
- 大口 健一, 佐々木 克彦, 石川 博將, 田上 道弘年次大会講演論文集 2000 175 - 176 一般社団法人日本機械学会 2000年In this paper, we discussed on the inelastic deformation of Sn-3.5Ag-0.75Cu solder alloys and its constitutive model. A series of basic tests, such as a pure tension, cyclic tension compression loading, and creep tests were carried out using Sn-3.5Ag-0.75Cu solder alloys. The test results showed that the inelastic deformation of the Sn-3.5Ag-0.75Cu solder alloys are affected by the strain rate and temperature. The applicability of the constitutive model previously proposed by authors to Sn-3.5Ag-0.75Cu solder alloys was also discussed by the comparison of experiments with simulation based on the constitutive model. As a result, it was found that the constitutive model can simulate the characteristics of deformation behavior of Sn-3.5Ag-0.75Cu solder alloys accurately.
- 佐々木 克彦, 石川 博將年次大会講演論文集 2000 179 - 180 一般社団法人日本機械学会 2000年In this paper, detailed experimental observation on the biaxial ratcheting behavior is conducted using a tubular specimen made of Type 304 stainless steel at room temperature. The test results show that the biaxial ratcheting strain occurs in spite of the zero superposed stress. We also constructed a constitutive model employing viscoplastic potential based on the dislocation density model (Estrin et al. [1996]). To explain the biaxial ratcheting deformation with the zero superposed stress, the latent hardening of an annealed material is considered in the evolution equation of the back stress.
- 柳本 陽征, 石川 博將, 佐々木 克彦年次大会講演論文集 2000 57 - 58 一般社団法人日本機械学会 2000年In this paper, FEM analysises of microelectronics solder joints subjected to cyclic thermal deformation were conducted. Pb free solder alloys (Sn-3.5Ag-0.75Cu) were chosen for the analysis, because of the regulation of using Pb/Sn solder alloys in near future. Results of Pb free solder alloys were compared with that of Pb/Sn solder alloys. Elasto-plastic, elasto-creep, and elasto-plastic-creep analysis were employed in this paper. As a result, it was found that the equivalent stress of Sn-3.5Ag-0.75Cu is much larger than that of Pb/Sn solder alloys, and that the elasto-plastic-creep analysis takes advantage of the simulation both of Pb free and Pb/Sn solder alloys.
- 高橋 剛, 佐々木 克彦, 永吉 隆, 辻村 明年次大会講演論文集 2000 517 - 518 一般社団法人日本機械学会 2000年Customers demand light-weight engines in addition to high power/torque and low fuel consumption. This is why aluminum alloys have been more often used for cylinder heads. Critical for the use of aluminum alloys for cylinder heads are strength and durability. Aluminum alloys, however, have complicated inelastic behavior under cyclic thermal condition, which prevents us from precise numerical analysis in estimating life. In our study, the mechanism of the low cycle fatigue and creep was clarified based on the mechanical properties of aluminum alloys, such as tensile, compressive, thermal fatigue and creep characteristics, which were determined by conducting tests on test pieces. The behavior of a cylinder head under cyclic thermal condition was reproduced by using a high-precision analysis method with cyclic creep taken into consideration.
- 佐々木 克彦, 眞山 剛, 石川 博將『日本機会学会論文集Ａ編』 66 649 1666 - 1673 2000年 [査読無し][通常論文]

Interaction between plastic and creep deformation is an important matter to construct a constitutive model for viscoplasticity. Particularly, equivalence of back stress affecting plastic deformation and affecting creep deformation takes an important role to descreibe cyclic viscoplastic deformation by a constitutive model. In this paper, to clarify the eqivalence, a serise of tests such as (1) Creep tests during pure tension and cyclic tension-compression loading, ( 2 ) cyclic tension-compression loading tests after both creep and pure tensile deformation, and (3 ) subsequent creep tests at a maximum stress after cyclic tension-compression loading, were carried out using Type 304 stainless steel at room temperature. The test results of (1) and ( 2 ) showed that the back stresses affecting plasticity and affecting creep have a same value. However, the difference subsequent creep curves were observed due to number of cycle of loading after the stress-strain relation were stabilized, irrespective of the same value of back stresses. Then, we tried to explaine the difference of the continuous creep curves using Bailey-Norton's transient creep law employed an activation energy. - K Sasaki, T Takahashi, H NumaoPROGRESS IN MECHANICAL BEHAVIOUR OF MATERIALS (ICM8), VOL 1 79 - 84 1999年 [査読有り][通常論文]
- 大口 健一, 佐々木 克彦日本機会学会論文集Ａ編 65 636 1795 - 1801 1999年 [査読無し][通常論文]

In this paper, we show the temperature effect on the deformation of 60 Sn-40 Pb solder alloys and its simulation using constitutive model for viscoplasticity. First, we investigate the temperature effect on the deformation of 60 Sn-40 Pb solder alloys from a series of tests, such as creep, pure tension and cyclic tension-compression loading tests. The larger temperature dependence of the solder alloys is found out. Applicability of the constitutive model that has been proposed previously to the temperature dependence of the solder alloys is verified. As a result, the parameters used in the model can be easily determined from the pure tension and the cyclic tension-compression loading test at several temperatures. It also can be found that the constitutive model can describe not only the temperature effect on the pure tension and the cyclic tension-compression loading but also the creep curves after preloading of cyclic tension-compression loading. - 佐々木 克彦ニホン キカイ ガッカイ ロンブンシュウ Aヘン 65 632 747 - 755 一般社団法人日本機械学会 1999年 [査読無し][通常論文]

Constitutive models for cyclic plasticity have been developed for about two decades. However, there are few constitutive models which can explain uniaxial ratchetting behavior accurately because of lack of knowledge of the correlation between uniaxial ratchetting and viscosity of materials. In this paper, to clarify the correlation, a series of experiments and numerical simulations are carried out. First, creep tests after the primary cyclic loading are conducted using Type 304 stainless steel at room temperature. Both uniaxial ratchetting and cyclic tension-compression loading controlled with strain amplitude are chosen for the primary cyclic loading. After the primary loading, subsequent creep tests are conducted at the maximum stress of the primary loading. Different creep curves are observed due to loading history of the primary loading, inspite of the same stress level of the subsequent creep tests. Moreover, the corresponding strain to creep during ratchetting deformation can be found out. Finally, the effect of the primary loading on the subsequent creep is also studied with the simulation using the dislocation based constitutive model. - Tsuyoshi Takahashi, Asao Koike, Katsuhiko SasakiSAE Technical Papers 107 454 - 461 1998年 [査読有り][通常論文]

Many methods for estimating the fatigue life of an aluminum alloy have been proposed in order to save development time and cost as demand for durable and light-weighted material grows strong. None of them, however, are practical enough to estimate the life of an engine component because thermal and mechanical loads on the engine component change as time elapses. Firstly, this paper deals with a method for clarifying the inelastic characteristics of an aluminum alloy, especially the effects of strain amplitude, ductile period (compression-tension cycle time) and temperature range on inelastic deformation, by making experiment where both thermal and mechanical loads were applied in the inverted phase('out-of phase'). Secondly the paper discusses a possibility of improving accuracy in determining the fatigue life of the material by introducing a new index of 'plastic work density per second', which is based on the conventional concept of plastic strain energy density. Copyright © 1998 Society of Automotive Engineers, Inc. - K Sasaki, H IshikawaMETALS AND MATERIALS-KOREA 4 3 533 - 536 1998年 [査読有り][通常論文]

Experimental observation and numerical simulation are conducted to clarify the effect of viscosity on deformation of materials. First, creep tests after the primary uniaxial ratcheting are carried out using Type 304 stainless steel. Specimens are subjected to cyclic tension-unloading with step and triangular waves during 20000 seconds as the primary ratcheting. After the ratcheting the subsequent creep test at the maximum stress is conducted during 20000 seconds. The experimental results show that the values of the subsequent creep strain after the ratcheting depend on the wave type and the time period of the ratcheting. The shorter time period of the ratcheting leads to the larger subsequent creep strain. Numerical simulations are also carried out using the constitutive model based on dislocation density [Estrin et al.]. As a result, the equivalent value of the ratcheting strain to creep strain is found out from the simulations and experiments. - 佐々木 克彦, 高橋 剛, 小池 朝夫『日本機会学会論文集A編』 64 617 58 - 65 一般社団法人日本機械学会 1998年 [査読無し][通常論文]

In this paper, out-of-phase thermo-mecahnical fatigue tests are performed on the aluminum alloy that is used for engines of automobiles. The tests are conducted with three constant total strain amplitudes, three periods of cycle of loading and three temperature renges. These test conditions are chosen taking account of actual use of the alloy in engines. First, the detailed observation on the inelastic deformation due to thermo-mechanical loading is done, and we show the effect of strain amplitude, period of cycle of loading and temperature range on the deformation of the alloy. Second, the method to estimate number of cycle to fatigue failure is discussed. As a result, the relationship between the plastic work density per unit time, which is based on the concept of the plastic strain energy density, and number of cycle to fatigue failure is expressed by a formula irrespective of the test condition. Then, it is found that the plastic work density per unit time has an advantage to estimate number of cycle to fatigue failure due to the thermo-mechanical loading. - H Ishikawa, K SasakiINTERNATIONAL JOURNAL OF PLASTICITY 14 7 627 - 646 1998年 [査読無し][通常論文]

Plastic-deformation induced anisotropy and memorization of back stress due to preloading affect the current loading. These phenomena are examined with tension and/or torsion tests, using SUS 304. Considering both anisotropy, and movement and memorization of back stress, equi-plastic surfaces are predicted. This explains the dependence of current loading on preloading well. Simulated strain paths during radial loading after shear straining show good agreement with experiments. (C) 1998 Elsevier Science Ltd. All rights reserved. - 佐々木 克彦情報の科学と技術 47 5 238 - 244 一般社団法人 情報科学技術協会 1997年企業図書館のアウトソーシングは本当に可能なのだろうか. アウトソーシングの導入を難しくしている原因を探り, 新しい方向性として, 書店をパートナーとしたマルチソーシングの提案を行う.
- 大口 健一, 佐々木 克彦, 石川 博將『日本機械学会論文集A』 63 609 954 - 961 一般社団法人日本機械学会 1997年 [査読無し][通常論文]

In this paper, we discuss the viscoplastic deformation and the constitutive model of 60Sn-40Pb solder alloys which is used for the connection of electronic packaging. The constitutive model is developed with the concept that the deformation includes the elastic, plastic, and creep deformation. which is caused from the strain rate effect on the deformation of the solder alloys. Namely, the constitutive model proposed in this paper combines the cyclic plastic model for the time independent part of deformation with the Norton's creep one for the time dependent part. The applicability of the model is verified from the comparison of the simulations based on the model for a series of tests, such as a pure tension and a cyclic loading under several strain rates. As a result, the constitutive model can predict the essential futures of the time dependent deformation of 60Sn-40Pb solder alloys. - 佐々木 克彦『材料』 46 3 295 - 301 1997年 [査読無し][通常論文]

In this paper, both the AE (Acoustic Emission) measurement and the microscopic observation of CFRP[±45°]4 subjected to cyclic tension-compression loading with a constant strain amplitude under a constant strain rate are conducted to verify the method to predict fatigue failure of CFRP, which was previously proposed by the present author from the microscopic change of the specimen. The method is based on the number of cycles to fatigue failure defined by using the relationship between the inelastic strain energy per cycle and cycle of loading. As a result, it is found that the relationship between the damage variable observed microscopically and cycle of loading is correlative with the relationship between the accumulated AE event count and cycle of loading. Moreover, it is also found that the number of cycles to fatigue failure determined by the proposed definition is coincide with the unique number of cycles observed from the relationship between the accumulated AE event count and cycle of loading. Thus, the method is considered verified from the microscopic structural change of CFRP[±45°]4. - H Ishikawa, K Sasaki, K OhguchiJOURNAL OF ELECTRONIC PACKAGING 118 3 164 - 169 1996年09月 [査読有り][通常論文]

This paper treats the prediction of fatigue life of 60Sn-40Pb solder alloy using the plastic strain work density per unit time calculated from the proposed constitutive model for cyclic viscoplasticity. Ar first, in order to verify the applicability of the proposed constitutive model to the deformation of 60Sn-40Pb solder alloy, a series of basic experiments, such as creep rests and cyclic tension-compression loading tests are performed at 303k: 323S 343K. Then, the proposed constitutive model is used to predict fatigue failure of the solder alloy. As a result, it is clarified that the proposed constitutive model is applicable to explain the viscous deformation of the solder alloy, and that its fatigue failure can be predicted using the plastic strain work density per unit time. - 1996年 [査読無し][通常論文]
**H. Ishikawa, K. Sasaki and K. Ohguchi : "Prediction of Fatigue Failure of 60Sn-40Pb Solder Using Constitutive Model for Cyclic Viscoplasticity", Trans. ASME, J. Electronic Packaging, 118(3) : 164-169 (1996)＊** - 大口 健一, 佐々木 克彦, 石川 博將『日本機械学会論文集Ａ編』 62 594 500 - 506 一般社団法人日本機械学会 1996年 [査読無し][通常論文]

In this paper, we propose a constitutive equation for cyclic viscoplasticity in which the viscoplastic potential function, the modified Prager-Ziegler kinematic hardening rule, and the Ramberg-Osgood law are incorporated. The applicability of the proposed constitutive equation to the deformation of 60Sn-40Pb solder alloys is Verified by a series of basic experiments, including a creep test and cyclic tension-compression test, which are performed at 303K, 323K and 343K. Moreover, fatigue tests are conducted at 303K, 323K and 343K to obtain the relation between the plastic strain work density per unit time and the number of cycles to fatigue failure. As a result, it is found that the fatigue failure of the 60Sn-40Pb solder can be successfully predicted using the plastic strain work density per unit time obtained from the simulation based on the constitutive equation. - K Sasaki, H IshikawaMATERIALS SCIENCE RESEARCH INTERNATIONAL 1 4 232 - 237 1995年12月 [査読有り][通常論文]

Fiber reinforced composite materials are widely used in many structures. It is well known that composite materials inelastically deform. Although there are some researches on fatigue failure, damage and crack propagation of composite materials, cyclic inelastic behavior of composite materials subjected to cyclic loading whose direction is different from that of the fiber has not been investigated in detail. In this paper, in order to investigate the cyclic inelastic behavior and the fatigue failure of composite materials, cyclic tension-compression loading under several conditions are carried out using laminated graphite/epoxy tubular specimens. The definition of fatigue failure is also discussed based on the test results. It is found that the CFRP subjected to cyclic loading shows the characteristic cyclic inelastic deformation. Moreover, using the concept of the plastic strain energy density and the concerned definition of fatigue failure, the relationship between the number of fatigue failure and the plastic strain energy density can be expressed by a formula. - K SASAKI, H ISHIKAWAJSME INTERNATIONAL JOURNAL SERIES A-MECHANICS AND MATERIAL ENGINEERING 38 2 265 - 272 1995年04月 [査読有り][通常論文]

A unified constitutive model which can predict cyclic plasticity, uniaxial and biaxial ratchetting, creep, and stress relaxation is required by designers of aeronautic equipment, nuclear reactors and so on. Detailed experimental observation of considering viscoplastic behavior of materials must be carried out to construct a unified constitutive model. In this paper, uniaxial and biaxial ratchetting tests and creep tests were carried out at room temperature and at 550 degrees C using SUS 304 stainless steel. As a result, it is clarified that uniaxial ratchetting behavior is affected by the viscous deformation of the material, and that biaxial ratchetting behavior is affected by both the viscous deformation of the material and the deformation caused by nonproportional loading. - Katsuhiko Sasaki, Hiromasa IshikawaJournal of the Society of Materials Science, Japan 44 232 - 237 1995年 [査読有り][通常論文]

Fiber reinforced composite materials are widely used in many structures. It is well known that composite materials inelastically deform. Although there are some researches on fatigue failure, damage and crack propagation of composite materials, cyclic inelastic behavior of composite materials subjected to cyclic loading whose direction is different from that of the fiber has not been investigated in detail. In this paper, in order to investigate the cyclic inelastic behavior and the fatigue failure of composite materials, cyclic tension-compression loading under several conditions are carried out using laminated graphite/epoxy tubular specimens. The definition of fatigue failure is also discussed based on the test results. It is found that the CFRP subjected to cyclic loading shows the characteristic cyclic inelastic deformation. Moreover, using the concept of the plastic strain energy density and the concerned definition of fatigue failure, the relationship between the number of fatigue failure and the plastic strain energy density can be expressed by a formula. © 1995, The Society of Materials Science, Japan. All rights reserved. - Katsuhiko Sasaki, Hiromasa IshikawaJSME International Journal, Series A: Mechanics and Material Engineering 38 2 265 - 272 1995年 [査読有り][通常論文]

A unified constitutive model which can predict cyclic plasticity, uniaxial and biaxial ratchetting, creep, and stress relaxation is required by designers of aeronautic equipment, nuclear reactors and so on. Detailed experimental observation of considering viscoplastic behavior of materials must be carried out to construct a unified constitutive model. In this paper, uniaxial and biaxial ratchetting tests and creep tests were carried out at room temperature and at 550°C using SUS 304 stainless steel. As a result, it is clarified that uniaxial ratchetting behavior is affected by the viscous deformation of the material, and that biaxial ratchetting behavior is affected by both the viscous deformation of the material and the deformation caused by nonproportional loading. - 佐々木克彦, 石川博將材料 44 505 1261 - 1266 1995年 [査読有り][通常論文]

This paper treats construction of the constitutive equation for inelastic behavior of CFRP, in which the damage effect is incorporated. At first, the authors propose an inelastic constitutive equation for CFRP subjected to cyclic loading. The constitutive equation is based on the constitutive model for cyclic plasticity proposed by the authors previously. Namely, the constitutive equation employs a damaged loading function that is similar to the loading function for metal alloys, the Ziegler type assumption to represent the movement of the damaged loading surface, and the Ramberg-Osgood stress-strain relation. To verify the applicability of the constitutive equation to the inelastic behavior of CFRP, a series of experiments, such as the cyclic tension-compression loading tests with several constant strain amplitudes, are carried out using laminated graphite/epoxy tubular specimens. The specimens have ±45 degree of fibers measured from the axial direction of the specimens. The predictions of the constitutive equation are compared with the experiments. As a result, it is found that the proposed constitutive equation can exactly predict the characteristic inelastic behavior of CFRP subjected to the cyclic loading, and that the damage variables are related to the strain amplitude of loading. © 1995, The Society of Materials Science, Japan. All rights reserved. - 佐々木克彦, 石川博將材料 44 498 332 - 337 1995年 [査読有り][通常論文]

Fiber reinforced composite materials are widely used in many structures. It is well known that composite materials inelastically deform. Although there are some researches on fatigue failure, damage and crack progagation of composite materials, the cyclic inelastic behavior of composite materials subjected to cyclic loading whose direction is different from that of the fiber has not been investigated in detail. In this paper, in order to investigate the cyclic inelastic behavior and the fatigue failure of composite materials, cyclic tension-compression loading under several conditions are carried out using laminated graphite/epoxy tubular specimens. The definition of fatigue failure is also discussed based on the test results. It is found that the CFRP subjected to cyclic loading shows the characteristic cyclic inelastic deformation. Moreover, using the concept of the plastic strain energy density and the concerned defintition of fatigue failure, the relation between the number of fatigue failure and the plastic strain energy density can be expressed by a formula. © 1995, The Society of Materials Science, Japan. All rights reserved. - H ISHIKAWA, K SASAKI, T NAKAGAWAJSME INTERNATIONAL JOURNAL SERIES A-MECHANICS AND MATERIAL ENGINEERING 37 4 347 - 354 1994年10月 [査読有り][通常論文]

One of the difficult problems in the study of the constitutive equation for cyclic plasticity is the prediction of ratchetting behavior that is induced by the superposition of a cyclic secondary load to a constant primary load in a biaxial case, or by the mean stress in a uniaxial case. This paper shows the constitutive equation in which the memorization of the back stress is considered for ratchetting behavior, especially for biaxial ratchetting behavior. To verify the applicability of the constitutive equation to ratchetting behavior, a biaxial ratchetting test was carried out using SUS 304 stainless steel at room temperature. As a result, it was found that the simulations based on the constitutive equation have good agreement with the tests. - CREEP, STRESS-RELAXATION AND BIAXIAL RATCHETTING OF TYPE-304 STAINLESS-STEEL AFTER CYCLIC PRELOADINGH ISHIKAWA, K SASAKIJOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME 116 2 133 - 141 1994年04月 [査読有り][通常論文]

A series of tests for creep, stress relaxation, and biaxial ratchetting of type 304 stainless steel after cyclic preloading were carried out to investigate their interaction. The interesting fact was pointed out that back stress in cyclic plasticity played an important role to describe creep, relaxation, and biaxial ratchetting following cyclic preloading. Then, the lest results showed that the material behavior due to creep after cyclic preloading could be represented by the modified Bailey-Norton law with stress levels evaluated from the current center of the yield surface, i.e., back stress which was determined by the hybrid constitutive model for cyclic plasticity proposed by the authors. In addition, biaxial ratchetting of axial strain induced by cyclic shear straining after cyclic preloading was expressed by the shear stress amplitude, the number of cycle and the axial stress level from the current center. - Hiromasa Ishikawa, Katsuhiko Sasaki, Takao NakagawaJSME International Journal, Series A: Mechanics and Material Engineering 37 4 347 - 354 1994年 [査読有り][通常論文]

One of the difficult problems in the study of the constitutive equation for cyclic plasticity is the prediction of ratchetting behavior that is induced by the superposition of a cyclic secondary load to a constant primary load in a biaxial case, or by the mean stress in a uniaxial case. This paper shows the constitutive equation in which the memorization of the back stress is considered for ratchetting behavior, especially for biaxial ratchetting behavior. To verify the applicability of the constitutive equation to ratchetting behavior, a biaxial ratchetting test was carried out using SUS 304 stainless steel at room temperature. As a result, it was found that the simulations based on the constitutive equation have good agreement with the tests. - F ELLYIN, Z XIA, K SASAKIINTERNATIONAL JOURNAL OF PLASTICITY 9 8 951 - 959 1993年 [査読有り][通常論文]

A series of uniaxial and biaxial cyclic tests with Proportional or nonproportional loading path and with different strain-rate histories are conducted on thin-walled circular cylindrical specimens of type 304 stainless steel. The results of these tests show that once a material is stabilized under a lower strain rate, the stress-strain response is not appreciably affected by a jump to a higher strain rate. A rate-dependent constitutive model recently proposed by ELLYIN and XIA [1991] has been extended to predict the above-mentioned strain-rate history effect. A comparison between the predictions of the extended model and the test results shows that most of the rate-dependent features of the material can be simulated by the model. - 石川博將, 佐々木克彦, 中川貴雄日本機械学会論文集（Ａ編） 59 569 1451 - 1457 1993年 [査読有り][通常論文]
- 石川博將, 佐々木克彦, 中川貴雄日本機械学会論文集（Ａ編） 59 558 360 - 366 一般社団法人日本機械学会 1993年 [査読有り][通常論文]

One of the difficult problems in the study of the constitutive equation for cyclic plasticity is the prediction of ratchetting behavior which is induced by the superposition of a cyclic secondary load to a constant primary load in the biaxial case, or by the mean stress in a uniaxial case. This paper shows the constitutive equation in which the memorization of the back stress was considered for ratchetting behavior, especially for biaxial ratchetting behavior. To verify the applicability of the constitutive equation to ratchetting behavior, biaxial ratchetting tests were carried out using type 304stainless steel at room temperature. As a result, it was found that the simulations based on the constitutive equation had good agreement with the tests. - H ISHIKAWA, K SASAKIJOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME 114 2 172 - 179 1992年04月 [査読有り][通常論文]

In order to study the applicability of the proposed hybrid constitutive model for cyclic plasticity to nonproportional loading, type 304 stainless-steel specimens subjected to sinusoidal loading that could change the degree of nonproportionality of the strain path were examined in detail. The subsequent yield surface during the loading was discussed in advance because the plastic deformation induced anisotropy coefficient tensor in the yield function had to be determined from the yield surface obtained by the experiment. From the experimental results, the subsequent yield surfaces during the loading could be assumed to be of the quadratic form of stress. The simulations based on the model gave a good description of the sinusoidal loading, irrespective of the degree of nonproportionality of the strain path. - K SASAKI, H ISHIKAWAPROCEEDINGS OF THE VII INTERNATIONAL CONGRESS ON EXPERIMENTAL MECHANICS, VOLS 1 AND 2 633 - 638 1992年 [査読有り][通常論文]
- F ELLYIN, Z XIA, K SASAKIANISOTROPY AND LOCALIZATION OF PLASTIC DEFORMATION 439 - 442 1991年 [査読有り][通常論文]
- 石川博將, 佐々木克彦, 大場 亮日本機械学会論文集（Ａ編） 57 544 2942 - 2948 一般社団法人日本機械学会 1991年 [査読有り][通常論文]

A series of tests for creep and biaxial ratchetting during cyclic loading were carried out to investigate the interaction between cyclic plasticity and creep or ratchetting of SUS 304 stainless steel. Specimens were subject to intermittent creep or biaxial ratchetting at several stress levels during cyclic tension-compression loading with the constant strain amplitude under the constant stress rate. The test results showed that the creep curve during cyclic loading could be explained by the so-called Bailey-Norton law, with stress levels measured from the current center of the yield surface which was determined by the hybrid constitutive equation for cyclic plasticity proposed by authors. Axial ratchet strain induced by cyclic shear stressing was expressed by the shear stress amplitude, the number of cycles and the axial stress level measured from the current center of the yield surface. - H ISHIKAWA, K SASAKIJOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME 112 4 471 - 476 1990年10月 [査読有り][通常論文]
- 佐々木克彦, 石川博將日本機械学会論文集（Ａ編） 56 532 2536 - 2542 一般社団法人日本機械学会 1990年 [査読有り][通常論文]

The recent study of the constitutive model for cyclic plasticity aims at the adequate description of additional hardening due to nonproportional cyclic loading, especially circular loading or, generally, sinusoidal loading. There is no constitutive equation which can describe additional hardening of nonproportional cyclic loading accurately. The authors have previously proposed the constitutive model for nonproportional cyclic loading, which could be called the hybrid constitutive model because the construction of the model is completed using the experimental results and the numerical simulation complementarily. In this study, additional hardening due to sinusoidal loading was carefully examined using SUS304 stainless steel, and the proposed model was applied to it. As a result, computer simulation based on this hybrid constitutive model can accurately describe the sinusoidal loading. - 石川博將, 佐々木克彦, 鈴木聖秀日本機械学会論文集（Ａ編） 56 532 2457 - 2463 一般社団法人日本機械学会 1990年 [査読有り][通常論文]

In this paper, the time-independent constitutive model of cyclic plasticity proposed previously is extended to the model of cyclic viscoplasticity, considering the motion of the center of the loading surface and plastic deformation-induced anisotropy. To construct the model, the effect of the variation in strain rate upon the stress-strain relationships is investigated by performing the tension -compression test with SUS304 stainless steel. The Ramberg-Osgood law is applied to each cycle with respect to the current center of the loading surface and the material constants in this model are determined from the test as a function of strain rate and strain amplitude. As a result, this model could accurately describe the cyclic viscoplastic behavior of the material. - H. Ishikawa, K. SasakiJournal of Engineering Materials and Technology, Transactions of the ASME 111 4 417 - 423 1989年 [査読有り][通常論文]

To formulate the constitutive equation for nonproportional cyclic loading, the influence of preloading on subsequent loading should be investigated experimentally. In this paper, both the stress-strain relation and the equi-plastic strain surface of subsequent loading after cyclic preloading have been examined carefully from combined tension-compression and torsion test with SUS304 stainless steel. The equiplastic strain surface could be represented by the quadratic form of stress when it was probed from the current center of the yield surface after cyclic preloading. Then, all the stress-strain curves of subsequent radial loading from the center were confirmed to be represented by the modified Ramberg-Osgood law. As a result, the modified Ramberg-Osgood law obtained shows availability to derive the constitutive equations of cyclic plasticity. © 1989 by ASME. - 石川博將, 佐々木克彦日本機械学会論文集（Ａ編） 55 516 1856 - 1864 一般社団法人日本機械学会 1989年 [査読有り][通常論文]

To formulate the constitutive equations for nonproportional cyclic loading, the influence of the preloading on the subsequent loading should be investigated experimentally. In this paper, the stress-strain relations and the equiplastic strain surfaces of the subsequent loading after the cyclic preloading were examined carefully from a combined tension-compression and torsion test with SUS304 stainless steel. Considering the movement of the center of the yield surface after the cyclic preloading, the equiplastic strain surfaces, which have been utilized for the determination of the material constant in the constitutive equations proposed previously, could be represented by the quadratic form of stress. As a result, the computer simulation based on this constitutive equation could accurately describe not only the stress-strain relations, but also the strain paths. - 石川博將, 佐々木克彦, 中島 清日本機械学会論文集（Ａ編） 55 513 1126 - 1132 一般社団法人日本機械学会 1989年 [査読有り][通常論文]

This paper deals with the cyclic plastic problem of a strip with a hole subjected to cyclic loading at the ends. For the numerical analysis, the constitutive model, in which the motion of the center of the yield surface is incorporated, is implemented in a finite element method. The distribution of strain and stress, and the development of the subsequent yield surface during cyclic loading are discussed in detail both for the zero and nonzero mean value of cyclic load. To verify the results of the computer simulations, the experiment of a strip with a hole of type 304 stainless steel is carried out. As a result, even the cyclic loading with nonzero mean value of cyclic load, strain at the bottom of the circular hole is ratchetted with increase of cycle, and stress and the subsequent yield surface approach to those due to the zero mean value of cyclic load. - H ISHIKAWA, K SASAKIJSME INTERNATIONAL JOURNAL SERIES I-SOLID MECHANICS STRENGTH OF MATERIALS 32 1 81 - 87 1989年01月 [査読有り][通常論文]
- H ISHIKAWA, K SASAKIJOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME 110 4 364 - 371 1988年10月 [査読有り][通常論文]
- 石川博將, 佐々木克彦日本機械学会論文集（Ａ編） 53 491 1432 - 1439 一般社団法人日本機械学会 1987年 [査読有り][通常論文]

In this paper a constitutive model for cyclic plasticity incorporating the motion of the center of the loading surface and the plastic deformation-induced-anisotropy has been proposed. The Ramberg-Osgood law is applied to each cycle with respect to the current center of the loading surface. The computer simulation based on this model is verified by virtue of several kinds of experiments on type 304 austenitic stainless steel. As a result, this model is confirmed to be adequate for describing the essential features of proportional and nonproportional cyclic straining.

- 佐々木 克彦 (担当:分担執筆範囲:Chapter 15, A Method to Evaluate Creep Properties of Solder Alloys Using Micro Indentation)
**From Creep Damage Mechanics to Homogenization Methods**

Springer 2015年01月 - 佐々木 克彦 (担当:分担執筆範囲:Viscoplastic Constitutive Model to Divide Inelastic Strain into Time-Independent and Time-Dependent Strains)
**Advanced Materials Modelling for Structures**

Springer 2013年10月 - 片桐一彰, 佐々木克彦, 垣辻篤 (担当:分担執筆範囲:第３章第９節カーボンナノチューブを用いた高熱伝導性材料による放熱技術)
**スマートフォン・タッチパネル部材の最新技術便覧**

技術情報協会 2013年 - 片桐一彰, 佐々木克彦, 垣辻篤 (担当:分担執筆範囲:第６章第１節カーボンナノチューブを配合した放熱材料～軽さを活かしたLED照明への応用～)
**これからの蓄・省エネルギー材料の開発における機能性付与技術**

技術情報協会 2013年 - 森北出版 2012年
**例題で学ぶ 品質管理** - 片桐一彰, 佐々木克彦, 垣辻篤 (担当:分担執筆範囲:第４章軽薄短小化に伴う「放熱対策」第４節カーボンナノチューブを用いた高熱伝導性材料の軽量化)
**新製品開発における軽薄短小化への新技術～スマートフォン，タブレットＰＣ，ディスプレイ，デジカメ，次世代自動車～）**

技術情報協会 2012年 - 佐々木 克彦 (担当:分担執筆範囲:pp.161-180)
**機械工学実用便覧第7版**

日本機械学会 2011年11月 - 片桐一彰, 佐々木克彦, 垣辻篤 (担当:分担執筆範囲:第７章 第６節 CNT／アルミニウム合金複材料)
**新版 複合材料・技術総覧，監修複合材料・技術総覧，監修複合材料・技術総覧，監修複合材料・技術総覧，監修複合材料・技術総覧**

2011年 - H. Ishikawa, K. Sasaki, T. Mayama (担当:分担執筆範囲:Equivalence of Back Stress during Plastic and Creep Deformation)
**IUTAM Symposium on Creep in Structure**

Kluwer Academic Publishers 2011年 - 佐々木 克彦 (担当:分担執筆範囲:材料力学)
**機械工学便覧 基礎編α３**

日本機械学会 2005年 - 佐々木 克彦 (担当:分担執筆)
**はんだのクリープ疲労試験法標準**

日本材料学会 2004年 - 佐々木 克彦 (担当:分担執筆)
**はんだのクリープ試験法標準**

日本材料学会 2004年 - H. Ishikawa, K. Sasaki (担当:分担執筆範囲:Section 4.7: Kinematic Hardening Rule for Biaxial Ratcheting)
**Handbook of Materials Behavior Models**

Academic Press 2001年

- 片桐 一彰, 佐々木 克彦, 粂 和弘, 山口 真平, 永廣 卓哉, 園村 浩介, 尾崎 友厚, 長谷川 泰則, 奥村 俊彦, 南 沙也加, 本田 真也M&M材料力学カンファレンス 2018年 一般社団法人 日本機械学会

Carbon fiber reinforced plastics (CFRP) has high strength and light weight properties. However, for impact load, an improvement has been required since resin matrix is weak. For CFRP manufacturing, the authors have developed the electro-activated deposition resin molding (EDRM) method to impregnate the resin, and the strength of CFRP for the static load was increased by the application of CNF without hydrophobic treatment. In this study, applying EDRM method, the impact strength of CFRP was improved by using cellulose nanofiber (CNF) without hydrophobic treatment. The electro-activated deposition solution contains polymer with epoxy group. The method was to apply the mixture of CNF dispersion and electro-activated deposition solution to the prepreg. After thermal curing, the CFRP which has CNF layer on the surface was obtained. The three-point bending test was carried out to confirm the static strength, and the impact strength was also confirmed by the Charpy impact testing.

- 片桐 一彰, 川北 園美, 木村 貴広, 武村 守, 吉岡 弥生, 佐々木 克彦, 本田 真也, 南 沙也加, 金 大貴, 山口 真平, 永廣 卓哉, 園村 浩介, 尾崎 友厚年次大会 2018年 一般社団法人 日本機械学会

For an efficient manufacturing method of CFRP, the electro-activated deposition molding method was developed. In this method, the carbon fiber fabric with curvilinear carbon fiber arrangement could be easily manufactured. The arbitrary arrangement of carbon fiber fabric can be woven by using embroidery machine, and was immersed in an electrodeposition solution containing an epoxy group and energized. Resin could be impregnated, after heat curing, CFRP was obtained. Impregnation is occurred in liquid, therefore, pressurizing process can be eliminated. So, autoclave became unnecessary, neither vacuum packing nor vacuum resin injection like VARTM (Vacuum assisted Resin Molding) method was required. In this study, tensile strength tests were conducted on the three kinds of CFRP specimens, with straight carbon fiber without hole, with hole in the center of specimen, and with controlling carbon fiber direction along principle stress. As a result, the maximum stress of the specimen with hole decreased to 82% of without hole. In case of the specimen with controlling carbon fiber direction along principle stress, the maximum stress recovered to 91% of without hole.

- 茅野皓輝, 本田真也, 片桐一彰, 佐々木克彦, 武田量 Dynamics & Design Conference (CD-ROM) 2021 2021年
- 上田修生, 本田真也, 佐々木克彦, 武田量, 鈴木逸人, 戸羽篤也, 鶴谷知洋 日本材料学会学術講演会講演論文集(CD-ROM) 70th 2021年
- 瀧澤拓, 本田真也, 片桐一彰, 佐々木克彦, 武田量 構造強度に関する講演会講演集 63rd 2021年
- 片桐一彰, PARK Tunsch, 山口真平, 本田真也, 佐々木克彦, 玉山雅人 飛行機シンポジウム講演集(CD-ROM) 58th 2020年
- CHEN Junnan, 佐々木克彦, 本田真也, 武田量, 大島伸行, 黒田明慈, 横山博一, LI Chenyu, 高嶋英厳 日本機械学会計算力学講演会論文集(CD-ROM) 32nd 2019年
- 佐藤史弥, 武田量, 佐々木克彦, 本田真也, 大島伸行, 横山博一 日本機械学会年次大会講演論文集(CD-ROM) 2019 2019年
- 片桐一彰, 山口真平, 川北園美, 奥村俊彦, 本田真也, 佐々木克彦, 粂和弘 日本機械学会M&M材料力学カンファレンス(CD-ROM) 2019 2019年
- 片桐一彰, 山口真平, 永廣卓哉, 川北園美, 園村浩介, 尾崎友厚, 舘秀樹, 吉岡弥生, 武村守, 南沙也加, 本田真也, 佐々木克彦 構造強度に関する講演会講演集 60th 2018年
- 片桐一彰, 山口真平, 永廣卓哉, 園村浩介, 尾崎友厚, 川北園美, 武村守, 吉岡弥生, 本田真也, 佐々木克彦, 南沙也加, 金大貴 日本複合材料合同会議(Web) 9th 2018年
- 片桐一彰, 山口真平, 永廣卓哉, 川北園美, 武村守, 吉岡弥生, 佐々木克彦, 本田真也, 南沙也加, LIGINE Florian 飛行機シンポジウム講演集(CD-ROM) 56th 2018年
- 片桐一彰, 山口真平, 永廣卓哉, 園村浩介, 尾崎友厚, 長谷川泰則, 奥村俊彦, 南沙也加, 本田真也, 佐々木克彦, 粂和弘 日本機械学会M&M材料力学カンファレンス(CD-ROM) 2018 2018年
- 片桐一彰, 佐々木克彦, 本田真也, 冨沢祐介, 中島晶, 南沙也加, 山口真平, 尾崎友厚, 園村浩介, 垣辻篤 構造強度に関する講演会講演集 59th 2017年
- 片桐一彰, 山口真平, 永廣卓哉, 尾崎友厚, 園村浩介, 吉岡弥生, 垣辻篤, 後藤凌平, 戸谷剛, 南沙也加, 本田真也, 佐々木克彦 宇宙科学技術連合講演会講演集(CD-ROM) 61st 2017年
- 片桐一彰, 山口真平, 永廣卓哉, 尾崎友厚, 園村浩介, 吉岡弥生, 垣辻篤, 南沙也加, 本田真也, 佐々木克彦 飛行機シンポジウム講演集(CD-ROM) 55th 2017年
- 木島雄大, 武田量, 横山博一, 黒田明慈, 大島伸行, 佐々木克彦 日本機械学会バイオフロンティア講演会講演論文集(CD-ROM) 28th 2017年
- 平野 裕貴, 武田 量, 奥住 啓介, 佐々木 克彦 バイオエンジニアリング講演会講演論文集 2016 (28) "1F31 -1"-"1F31-5" 2016年01月09日The objective of this study was to clarify the contribution of the anterior cruciate ligament (ACL) on the knee joint stability. The ACL consists of three ligament bundles, each with their own different function. Based on the ACL triple bundle theory, a porcine stifle joint with the anteromedial bundle (AMB), intermediate bundle (1MB) and posteromedial bundle (PLB) was prepared. The knee joint was placed in a material testing machine capable of releasing/constraining 5 DoFs of the knee. The load contribution of each bundle was estimated by, sequentially cutting each bundle from the knee joint and measuring the load during an anterior-posterior drawer test. As a result, large decrease in the load contribution was observed when 1MB and PLB were cut, however only a small contribution was seen for the AMB.
- Tomizawa Yusuke, Sasaki Katsuhiko, Kuroda Akiyoshi, Kaito Yoshihiko Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2015 (14) 210 -210 2015年10月04日
- 武田 量, 奥住 啓介, 佐々木 克彦 バイオフロンティア講演会講演論文集 2015 (26) 95 -96 2015年10月01日
- Takeda Ryo, Okuzumi Keisuke, Kawaguchi Yasuyuki, Sasaki Katsuhiko Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 307 -307 2015年09月16日
- Yu Lu, Okuzimi Keisuke, Takeda Ryo, Sasaki Katsuhiko Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 292 -292 2015年09月16日
- Syaifudin Achmad, Takeda Ryo, Sasaki Katsuhiko Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 265 -265 2015年09月16日
- Tomooka Yukiko, Sasaki Katsuhiko, Takeda Ryo Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 272 -272 2015年09月16日
- 星野 あまね, 黒田 明慈, 佐々木 克彦, 武田 量 年次大会 : Mechanical Engineering Congress, Japan 2015 "S0220304 -1"-"S0220304-5" 2015年09月13日Stenting is a common treatment of stenosis. One of problems of stent treatment is restenosis. Local hemodynamic factor such as low wall shear stress (WSS) is one of the reasons for restenosis. Therefore, blood flow analyses have been performed to clarify the restenosis mechanism. Fluid-Structure Interaction (FSI) is used for blood flow analysis to consider the interaction between fluid pressure and structure deformation. In this research, the effects of the deformed vessel by stenting and pulsating flow are analyzed using FSI. The stent expansion analysis was performed to obtain the deformed shape using FEM analysis software ANSYS Mechanical APDL. FSI analysis was performed to examine the effect of a pulsating vessel using ANSYS Workbench. An initial stent model was made based on the shape of before the expansion. The expanded stent model was also made based on the shape of the expanded stent. To reveal the effect of pulsatile on the blood flow after the stenosis, two boundary conditions were employed; rigid wall and FSI. Inlet flow rate was assumed to be expressed by a periodic function to reproduce the pulsating flow in the carotid artery. The results of velocity, pressure difference and WSS are shown for each model and condition. In the case of rigid wall, WSS at the stenting site is reduced by the expansion of the vessel.
- 瀧田 敦子, 佐々木 克彦, 大口 健一 年次大会 : Mechanical Engineering Congress, Japan 2015 "J0410205 -1"-"J0410205-5" 2015年09月13日To evaluate the strength reliability of the electronic substrate accurately, the deformation behavior, especially, the creep deformation of the solder joint should be estimated in-situ. The indentation creep test is one of the effective test to evaluate the creep deformation in the microscopic region. However, this test has the problem that the stress is overestimated by employing the contact area between the indenter and the specimen as the reference of the stress evaluation. To solve the problem, methods to determine the suitable area for the indentation test and to evaluate the creep deformation by using the suitable area were numerically proposed by the authors. In the proposed method, the principal stress plane approximated by the spherical surface is defined as the reference area to calculate the stress assuming that the specimen is homogeneous. In this paper, the indentation process is simulated by using the inhomogeneous model of the specimen to confirm that the principal stress plane is assumed as the spherical surface. The actual indentation test with a constant depth process is also conducted using Sn-3.0Ag-0.5Cu solder specimens to verify the applicability of the proposed method to the actual indentation test.
- 宮下 貴行, 吹谷 嵩文, 佐々木 克彦, 柳沢 祐介, 茅野 林造 年次大会 : Mechanical Engineering Congress, Japan 2015 "J0410204 -1"-"J0410204-5" 2015年09月13日Heat treatment is ordinarily conducted to reduce residual stress caused by plastic work. Also to improve physical properties of steel, such as tensile strength, heat treatment is conducted. For example, an appropriate way of quenching leads to compressive stress to improve of fatigue strength. To obtain an optical condition of the heat treatment, it is important to understand the phase transformation during the heat treatment. In the case of large forging, especially, the scale effect induces temperature difference inside the steel and it makes difficult to consider the phase transformation due to the heat treatment. Therefore a method to quantitatively evaluate the residual stress after hear treatment of large forging steal is required. In this paper, in the aim at reduction of heat treatment processes of a large size forged steel, finite element method (FEM) is conducted to find an optical condition of the heat treatment. The analysis considers the effects of both transformation plasticity and creep deformation. Furthermore, the transformation plastic deformation are also considered. Finite element analysis software ANSYS14.5 is used with user subroutine "Usermat".
- 多田 明央, 廣瀬 諒典, 佐々木 克彦, 今西 輝光, 伊藤 洋平 年次大会 : Mechanical Engineering Congress, Japan 2015 "J0410506 -1"-"J0410506-5" 2015年09月13日This paper presents the mechanical property of Aluminum based composites containing of carbon fibers (CF), carbon nano-tubes and graphite. Recently there are many researches on the reinforcement using these fibers from the view point of saving energy and resource because of their remarkable strength and thermal performances; thermal conductivity, tensile strength, specific strength, and so on. Especially, aluminum based composites of carbon fibers are expected to be applied to heat exchangers and heat sink, for example. To reveal the strength properties of the composite materials, tensile tests are conducted. The results show that Graphite makes composite brittle, CF makes Young's modulus of composite a little bit higher if the volume fraction of CF is from 30 to 50 vol%.
- 于 路, 奥住 啓介, 武田 量, 佐々木 克彦 年次大会 : Mechanical Engineering Congress, Japan 2015 "J1630201 -1"-"J1630201-4" 2015年09月13日Patients suffering from knee joint damage are generally only provided with subjective, qualitative feedback form physicians. This research sets the foundation for providing a quantitative, non-invasive feedback for knee joint damage by finding the center of rotation (CoR) of the knee joint. Knee joint motion analysis is usually performed through camera based optical tracking systems. Although these standard technologies allow a complete 3-D kinematics of knee, they require a dedicated laboratory. In this research a novel method of utilizing IMUs to obtain knee CoR is proposed. The merits of utilizing IMUs derives from its compact size, short diagnose time, thus putting less burden on patients. With IMU, acceleration and angular velocity can be measured. IMUs were fixed to the thigh and shank to measure the instantaneous CoR of the knee. Since the instantaneous CoR of the knee is different during normal and damaged condition, by obtaining the instantaneous CoR of the knee, one can quantitatively evaluate the conditions of the knee and provide outcome evaluation after surgery. It was found that for extension motion, good correlation coefficient was obtained from IMU and camera. However flexion motion showed much larger result than camera. This is assumed as the effect of inertia. In addition, calculating a 3D motion in a 2D plane may be a crucial reason effecting results. However it can be concluded that utilizing IMUs to diagnose knee function is adoptable in clinical fields for its easy accessibility and less burdens on patients.
- 友岡 由紀子, 佐々木 克彦, 武田 量 年次大会 : Mechanical Engineering Congress, Japan 2015 "S0220305 -1"-"S0220305-5" 2015年09月13日This paper describes an effect of using new ferrous polycrystalline shape-memory alloy showing huge superelasticity and higher stiffness as a self-expanding stent material. In this research, stent deployment analysis was conducted by using finite element analysis (FEM) software ANSYS 15.0. Nitinol self-expanding stents are widely used for artery stenosis treatments due to their high flexibility. However, the radial stiffness of self-expanding stents is low compared to balloon-expanding stents. Stent, artery, plaque, and sheath models were made for FEM analyses and the analytical results after deployment of nitinol and ferrous alloy stents were compared. In addition, two methods of the unsheathing were studied: (1) the conventional method where a stent comes out from one end of the sheath and (2) a new method in which stent comes out from the center of the sheath. FEM results showed that the radial force of the stent made of the new ferrous alloy was higher than those of nitinol. Meaning that the ferrous alloy stent displaces the plaque more than the nitinol stent. Furthermore, the plaque was displaced more using the new method of unsheathing, and the ends of the artery without the plaque showed smaller displacement. These results suggest the effectiveness of using the ferrous alloy for self-expanding stent.
- 瀧田 敦子, 佐々木 克彦, 大口 健一 計算力学講演会講演論文集 2014 (27) 870 -872 2014年11月22日
- 冨沢 祐介, 黒田 明慈, 佐々木 克彦, 海藤 義彦, 松田 和幸 熱工学コンファレンス講演論文集 2014 "B121 -1"-"B121-2" 2014年11月08日As smart phones become more complex, higher in performance and smaller in size, heat concentration at localized areas is becoming a problem. Phase change materials (PCM) have drawn attention as passive thermal management. In this study, simple experiments using PCM were conducted. The results showed that the saturation time increased with increase in the mass of PCM, and a relationship between the saturation time and the mass of PCM was a linear relation. Furthermore, the saturation time increased with decrease in the melting temperature of PCM. As a result, PCM is effective for the thermal management of smart phones.
- 奥住 啓介, 武田 量, 于 路, 佐々木 克彦 バイオフロンティア講演会講演論文集 2014 (25) 115 -116 2014年10月02日
- 高橋 和希, 佐々木 克彦, 瀧田 敦子, 大口 健一 北海道支部講演会講演概要集 2014 (53) 23 -24 2014年09月27日
- SYAIFUDIN Achmad, 佐々木 克彦, 武田 量 年次大会 : Mechanical Engineering Congress, Japan 2014 "S0220204 -1"-"S0220204-4" 2014年09月07日The changes in physical surface condition after expansion of balloon expandable stent are known as the primary cause of some serious problem following narrowed arteries treatment. The shape of a balloon in the treatment of eccentric plaque, which is majority form of plaque, is hypothesized influencing stent surface roughness. In this paper, the influence of the balloon shape on the changes in surface roughness will be observed using finite element method. Transient nonlinear structural analyses of eccentric plaque are built to identify the deformation. General-purpose software of finite element method such as ANSYS is used for the structural analyses. Material properties utilized in the simulation are 316 stainless steel for the stent; polyethylene terephthalate (PET) for the balloon; hypo cellular for the plaque; and carotid artery for the vessel wall. 3D symmetrical model will be developed in order to reduce computational time. Type Palmaz stent is determined for modeling in the structural analysis. Type cylindrical and offset balloon shape is chosen in the analysis, which one gives better treatment for eccentric plaque. The eccentric plaque is designed having a slight longer length than the stent, which is covering almost 75% blood vessel hole so that covers in one side of vessel wall surface and another side is allowed free from plaque disruption. The material models are defined as multilinear isotropic for stent and hyperelastic for the balloon, plaque, and arterial wall. The finite element analysis indicated that offset balloon shape succeeds to reduce stress intensity area on the vessel wall and helps to improve foreshortening and dogboning effects. Nevertheless, several structural developments of Palmaz stent should be conducted to adapt the expansion direction of offset balloon because its directional expansion also increase plastic deformation of another stent struts.
- 瀧田 敦子, 佐々木 克彦, 大口 健一 年次大会 : Mechanical Engineering Congress, Japan 2014 "J0410301 -1"-"J0410301-4" 2014年09月07日Estimation methods for the creep properties by measuring the micro size deformation is required for finite element method (FEM) analysis considering the creep deformation of the solder joint in-situ. The indentation creep test is one of the effective methods to directly evaluate the creep deformation of solder joint. However, the indentation test cannot give the same creep properties as the creep properties obtained by the uniaxial creep tests using a bulk specimen. The authors proposed an indentation test conducted under a constant depth to determine a suitable reference area, which leads to the same creep characteristics as those obtained by the uniaxial creep test. One of the remaining problems of the indentation test is the reference area cannot be determined without the creep data obtained by the uniaxial creep test. In this paper, a method to determine the reference area without the uniaxial creep tests using a bulk specimen is proposed. For the determination of the new reference area, numerical indentation tests under a constant depth process for four kinds of solder alloys were conducted by FEM. The numerical simulation showed that the reference area obtained considering the distribution of the principal stress gives the almost same creep characteristic as that obtained by the uniaxial creep using bulk specimens.
- HASAN Md. Kamrul, 佐々木 克彦 年次大会 : Mechanical Engineering Congress, Japan 2014 "G0310103 -1"-"G0310103-5" 2014年09月07日Transformation of conventional energy systems to renewable energy can limit the climate change to a safe level. Among the sources of renewable energy, solar energy is more convenient and easy to access. However, high cost of silicon wafer is a problem for photovoltaic solar cells. Therefore, manufacturers need to the development of solar cells made of thinner crystalline silicon wafer as a way to reduce costs. Silicon is brittle, and thinner silicon is easier to break due to residual stress induced during soldering process under high temperature. The solar cell conductive film (CF) can bonds the solar cell with metal ribbon at lower temperature than soldering. After the manufacturing process when the solar panel is subsequently exposed to sunlight for its operation, the temperature distribution redistributes the residual stress. Therefore, it is necessary to know how silicon wafers of different thicknesses are deformed for the two bonding materials, solder and CF in order to find out a reliable bonding option for thinner silicon. This study used the finite element method (FEM) to analyze the thermal deformation during the manufacturing and using processes of solar cells with different thicknesses of silicon wafer. It was found that varying the thickness of silicon wafer has long term effects on the deformation and residual stress. Sn-3.5Ag solder and CF were employed as the bonding interface to carry out a comparison of the thermal deformation characteristics.
- 武田 量, 于 路, 奥住 啓介, 佐々木 克彦 年次大会 : Mechanical Engineering Congress, Japan 2014 "G0210104 -1"-"G0210104-4" 2014年09月07日This paper proposes a novel method for estimating the knee joint center of rotation (CoR) using inertial sensors. The inertial sensors used in this work contain tri-axial accelerometers and gyroscopes. The inertial sensors are attached to the femur and tibia segments of the leg and are capable of measuring the acceleration and angular in all 3 axes simultaneously. The angular velocity data was used to calculate the rotation angle around the CoR and the centrifugal acceleration was used to calculate the distance from the inertial sensor to the CoR. Experiments were carried out in two stages: preliminary pendulum experiment and measuring the flexion-extension motion of the human knee. In both experiments the accuracy of the sensor's distance to the CoR was evaluated. The preliminary pendulum experiment showed correlation coefficient (CC) of over 0.99 whereas the human flexion-extension motion showed lower CC and the average absolute error was about 5.1 cm. Improvements such as a countermeasure for attachment errors/skin motion and consideration for other rotational motions such as internal-external rotation and varus-valgus rotation should be considered to further increase the accuracy of the proposed method.
- HASAN Md. Kamrul, 佐々木 克彦 M&M材料力学カンファレンス 2014 "OS0508 -1"-"OS0508-3" 2014年07月19日Aiming at understanding the thermal deformation characteristics of two solar cell configurations, finite element thermal stress analysis is carried out in this investigation. This study covers the manufacturing process and operating conditions including three thermal cycles of different environments in order to determine the long term effects of residual stresses. While the first solar cell model is tabbed by lead-free solder, the second model by conductive film (CF). A high temperature soldering process causes stress of the solar cell due to the different thermal expansion coefficients of materials; stress could weaken the bond and reduce reliability of the cell. Also when a photovoltaic (PV) module is placed under the sun, solar irradiation will generate a temperature distribution across its surface. The conductive film requires lower temperature for its bonding with beautifully finished bonded areas. In this study, first, finite element analysis (FEA) was carried out for manufacturing process using both solder and CF bonding. Then, three temperature cycles considering different environmental operating conditions were applied to the analysis to understand how thermal cycles affect the residual stress developed during manufacturing process of solar cell. Using times of six months for solder and one month for CF bonded cell were considered for the analysis. This investigation provides a comparison of thermal stress between solder and CF as bonding materials of solar cells in order to determine which offers best reliability in the long term.
- 瀧田 敦子, 佐々木 克彦, 大口 健一 M&M材料力学カンファレンス 2014 "OS0507 -1"-"OS0507-2" 2014年07月19日To evaluate the strength reliability of electronic substrate by the accurate structural analysis, the method to evaluate the creep deformation of in-situ solder joints must be developed. The Indentation creep test is one of effective method to evaluate the creep deformation in microscopic specimen. It is required that the result obtained by the indentation creep test is should be expressed by the constitutive equation for the creep deformation under the uniaxial stress evaluated by the tensile creep test In this paper, the indentation creep test at IN loading for 9000s duration is conducted by experiment and the result obtained by the indentation creep test is compared with that obtained by the tensile creep test using the bulk specimen. As the result, the result obtained by the indentation creep test did not coincide with that obtained by the tensile creep test To explain the difference, the numerical indentation creep test is conducted. Finally, the method to determine the suitable reference area for calculating uniaxial stress of the indentation test is proposed. The reference area determined by the new indentation test is the effective to obtain the reasonable creep curves by the indentation test.
- 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐一彰, 垣辻篤 釧路工業高等専門学校紀要 (47) 123 -126 2013年12月 [査読無し][通常論文]
- 山本 賢, 佐々木 克彦, 片桐 一彰 機械材料・材料加工技術講演会 M&P 21 4p 2013年11月08日 [査読無し][通常論文]
- 冨沢 祐介, 黒田 明慈, 佐々木 克彦, 海藤 義彦, 松田 和幸 熱工学コンファレンス講演論文集 2013 255 -256 2013年10月18日As smart phones become more complex, higher in performance and smaller in size, heat concentration at localized areas is becoming a problem. Therefore, the aim of this paper is to examine the effect of high thermal conductive materials for heat dissipation in order to solve this problem. The thermal conductivity of the outer case of the smart phone was changed using finite element method (FEM) to simulate high thermal conductive materials or composite materials with anisotropy. The maximum temperature gradually decreased and the minimum temperature gradually increased with increasing the thermal conductivity of the outer case. Moreover, the thermal conductivity in the longer direction of the smart phone was important for lowering the maximum temperature. In this paper, it is found that applying high thermal conductive materials to the outer case is effective for uniforming the heat dispersing.
- 吹谷 嵩文, 佐々木 克彦, 黒田 明慈, 武田 量 北海道支部講演会講演概要集 2013 (52) 23 -24 2013年09月28日
- 佐々木 克彦, 片桐 一彰, 永井 明夫 マイクロエレクトロニクスシンポジウム論文集 23 17 -20 2013年09月12日 [査読無し][通常論文]
- 瀧田 敦子, 佐々木 克彦, 大口 健一 年次大会 : Mechanical Engineering Congress, Japan 2013 "J042022 -1"-"J042022-3" 2013年09月08日To accurately evaluate the strength reliability of solder joint by FEM analysis, the method to evaluate the creep distribution of solder joints in-situ must be developed. The indentation creep test is an effective method to evaluate the creep distribution of solder joints in-situ. However, the stress calculated using this method is overestimated when compared with that obtained by tensile creep test using bulk specimen. In this paper, a new indentation test to evaluate the creep deformation using a new reference area was proposed. The proposed method provided the same stress as that obtained by tensile creep test This method consists of two kinds of indentation tests. The first test is maintaining the indentation depth constant at different depths and the second is an indentation creep test where a constant load is maintained for various loads. Assuming the specimen of this research is Sn-3.0Ag-0.5Cu solder alloy, the feasibility of this method was confirmed using FEM analysis. As a result, a new reference area appropriate for the indentation creep test was defined. At the same time, the same evaluation result as that obtained by tensile creep test was provided by the indentation creep test considering new reference area. Hence, it will be possible to evaluate the steady-state creep deformation of the new material by this evaluation method.
- 奥住 啓介, 劉 〓, 武田 量, 佐々木 克彦 年次大会 : Mechanical Engineering Congress, Japan 2013 "J164012 -1"-"J164012-5" 2013年09月08日This paper presents a method of measuring knee joint motion for clinical diagnostic procedures. MRI or optical tracking methods are examples of existing methods to quantify diagnostic procedures for assessing knee joint ligament injury. However, these methods require a large amount of space and are quite expensive. An alternative method is to use multifunctional sensors which contain tri-axial accelerometers and gyroscopes. Accelerometers can measure the tilt angle against the gravity vector and estimate the translational acceleration. Gyroscopes can measure the angle of rotary motion. An angle obtained by a gyroscope is normally influenced by noise; causing a bias in angle. This work presents a system using a Kalman filter to remove the bias angle obtained by the gyroscope. Experiments that measure three rotary motions and a translational motion of the knee joint were conducted. Sensors are mounted on the Tibia and Femur bone of a knee joint model. It was found that the bias of the gyroscope's output was minimized in all three rotary motions by applying the proposed system. In addition, translational distance was calculated by integrating the accelerometer's output. However, distance obtained by acceleration is significantly influenced by noises due to double integration. A method to process the acceleration data and obtain translational distance is also proposed.
- 菊池 久里馬, 福田 尚之, 佐々木 克彦, 小枝 日出夫, 柳沢 祐介 年次大会 : Mechanical Engineering Congress, Japan 2013 "G031043 -1"-"G031043-3" 2013年09月08日Choosing the appropriate heat treatment condition of large forging is important for reducing production cost and to guarantee the quality. This is due to the fact that the strength and the accuracy of large forging are greatly influenced by the residual stress. The residual stress is the stress that remains after the heat treatment and is the cause of cracks and reduces the lifetime of materials. The stress is brought about by strain that occurs due to phase transformation and unbalanced temperature distribution. The unbalanced temperature distribution is caused by the difference in cooling rates within the material. A method for quantitative evaluating the residual stress of large forging has not been fully established. In this research, the analytical cooling curves are determined by optimizing heat transfer coefficient between steel and the circumferential fluid, so the difference to the experimental cooling curves are minimized. Using the obtained cooling curves, residual stress is analyzed. Finite element analysis software ANSYS 13.0 is using. The parameters using in the analyses are temperature dependent considering phase transformation of austenite to bainite. The analytical results of the residual stresses compared to the experimental ones, and the validity is examined.
- 山田重和, 松浦清隆, 大野宗一, 佐々木克彦, 垣辻篤, 片桐一彰 日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2012 2013年
- 柳沢 祐介, 小枝 日出夫, 佐々木 克彦 機械材料・材料加工技術講演会講演論文集 2012 (20) "612 -1"-"612-4" 2012年11月30日
- 瀧田 敦子, 大口 健一, 佐々木 克彦 年次大会 : Mechanical Engineering Congress, Japan 2012 "J061034 -1"-"J061034-5" 2012年09月09日For design of high-density electronic package, FEM analyses evaluate strength reliabilies of solder joint should be conducted considering the distribution of the creep deformation in the solder joints. To obtain accurate results of the structural analyses of the solder joints, a method to evaluate the steady-state creep deformation in-situ must be developed. Indentation creep test is one of the effective method to evaluate the creep distribution of the solder joints, however, the tests have some problem such as that the creep strain obtained by the method does not gives the same results as that obtained by pure tensile tests using balk specimens. In this paper, FEM analyses of indentation creep test at IN loading for 9000s duration were conducted to confirm that the steady creep deformation obtained by the indentation creep test does not coincide with that by the pure tensile tests using the bulk specimen. A new method to evaluate the steady-creep deformation of solder joints using the indentation creep tests is proposed. The method employs a reference surface of an indenter to clarify the correlation between the creep deformation obtained by a bulk specimen and that by the indentation. As results, it is found that the steady creep deformation obtained by the new method of the indentation creep test coincides with that by the pure tensile test using the bulk specimen.
- 佐々木克彦, 黒田明慈, 片桐一彰, 片桐一彰, 高橋教雄, 高橋教雄, 永井明夫, 永井明夫, 伊藤洋平, 伊藤洋平, 垣辻篤 Thermophysical Properties 33rd 2012年
- 伊藤洋平, 伊藤洋平, 片桐一彰, 片桐一彰, 高橋教雄, 高橋教雄, 永井明夫, 永井明夫, 垣辻篤, 佐々木克彦 Thermophysical Properties 33rd 2012年
- 佐々木克彦, 片桐一彰, 高橋教雄, 永井明夫, 伊藤洋平, 垣辻篤 日本複合材料合同会議(CD-ROM) 3rd 2012年
- 安藤 佑, 佐々木 克彦 学術講演会講演論文集 61 219 -220 2012年
- Katsuhiko Sasaki, Kazuaki Katagiri, Norio Takahashi, Akio Nagai, Yohei Ito, Atushi Kakitsuji 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition AIAA 2012-1007 2012年 [査読無し][通常論文]

Improvements of thermal conductivity of aluminum based composites containing CNT-VGCF networks, which may be used for the cooling device of Insulated Gate Bipolar Transistors (IGBT) for aerospace, are discussed in this paper. The composite is fabricated by Spark Plasma Sintering (SPS) from aluminum powder and vapor grown carbon fiber (VGCF). It has been found that the small amounts of CNT addition to the composites increase in the thermal conductivity of the VGCF-aluminum composites because the VGCF-CNT network is constructed. To improve the thermal conductivity of the VGCF/CNT-aluminum composites, CNT is subjected to additional heat treatments using SPS. The measurements of Raman spectrophotometry shows that the defect band dramatically decreases and that the unit surface and G/D ratio are improved by heat treatment. The observation of scanning electron microscope (SEM) also shows that CNT is bundled by the heat treatment. Finally, it is found that the composites containing the heat-treated CNT have the larger thermal conductivity than the composite containing the non-heat-treated CNT. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. - 安藤 佑, 佐々木 克彦, 黒田 明慈 北海道支部講演会講演概要集 2011 (50) 53 -54 2011年10月01日
- 中村 孝, 奈良林 直, 菊地 優, 佐々木 克彦, 成田 吉弘, 松浦 清隆 工学教育研究講演会講演論文集 23 (59) 318 -319 2011年08月22日
- 佐々木 克彦, 福田 尚之, 高橋 和彦 M&M材料力学カンファレンス 2011 "OS1503 -1"-"OS1503-3" 2011年07月16日In this paper, surface roughness of stainless steel SUS316NG used for piping systems of nuclear power plants is measured after the stainless steel is subjected to a several amounts of plastic deformation up to 18%. The two types of surface roughness such as line(1D) roughness and area(2D) roughness are measured by using the 3D color laser microscope. The 2D roughness in a crystal is also measured. The measurements show that there is a difference in 1D roughness due to the location of measurements of the specimen after deformation, while the value of the 2D roughness does not vary due to the location. It can be also found that the 2D roughness is well proportional to the plastic deformation. The linear relationship between the 2D roughness and plastic deformation can be also seen in small strain range under a few percents, which suggests that a possibility to estimate the plastic deformation using measured surface roughness.
- 垣辻篤, 佐々木克彦, 伊藤洋平, 永井明夫, 片桐一彰 日本金属学会講演概要(CD-ROM) 149th 2011年
- 福田 尚之, 佐々木 克彦, 高橋 和彦 学術講演会講演論文集 60 287 -288 2011年
- SHIMANAKA Kazuya, FUKUCHI Kohei, SASAKI Katsuhiko, KATAGIRI Kazuaki, IMANISHI Terumitsu, KAKITSUJI Atsushi Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2011 (0) _OS16 -2-4- 2011年 [査読無し][通常論文]
- Daisuke Echizenya, Hiroo Sakamoto, Katsuhiko Sasaki 11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 1440 -1445 2011年 [査読無し][通常論文]

Solar power generation using polycrystalline silicon wafers has been rapidly growing in recent years. As a result, it is required to understand the strength characteristics of polycrystalline silicon wafers in order to enhance their quality. Scratches and material defects should be taken into consideration when strength characteristics of polycrystalline silicon are evaluated, since it is a brittle material. In this paper, bending strength of polycrystalline silicon wafers for solar cells were measured, and evaluation regarding the cause of different strength values, which depend on manufacturing conditions of the wafer, was conducted based on fracture mechanics. Residual stress measurements using Raman spectroscopic and observation with TEM (Transmission Electron Microscope) were also conducted. The results clarified the existence of numerous cracks on the wafer surface that are assumed to be generated during slicing process. Thus, it was confirmed that wafer strength depends on the level of machining damage in slicing process. We can establish high reliability for PV modules as a result of modifying the slicing conditions to minimize the mechanical surface damage on wafers and increase the wafer strength. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - Kohei Fukuchi, Katsuhiko Sasaki, Kazuaki Katagiri, Terumitsu Imanishi, Atsushi Kakitsuji 11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 912 -917 2011年 [査読無し][通常論文]

This paper treats aluminium (Al) based composites containing vapor-grown carbon fibers (VGCF) and carbon nanotubes (CNT) having very high thermal conductivity. To apply the composites to real used conditions, the interaction between thermal and mechanical properties should be clarified. Therefore, tensile tests are conducted to clarify strength of the composites at several temperatures. The thermal conductivities are measured before and after tensile tests to clarify the dependence of the deformation on the thermal conductivity. Theoretical discussion is also conducted using Nan model and finite element method (FEM). The simulations reasonably explain the deformation dependences of the thermal conductivity of composites. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - Ken-ichi Ohguchi, Katsuhiko Sasaki 11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) 10 1139 -1144 2011年 [査読無し][通常論文]

Finite element analyses for evaluating fatigue strength of solder joints in electronic packages should employ a constitutive model which can describe cyclic deformations precisely. Therefore, the model should be constructed based on detailed information about the inelastic strain generated under the cyclic loading. We previously investigated both the plastic and creep strains of Sn-Ag-Cu (SAC) lead-free solder under cyclic loading experimentally by conducting cyclic loading tests using stepped ramp waves. In this study, we construct an elastic-plastic-creep constitutive model based on the experimental results, such as the stress-plastic strain relations, and the stress-creep strain relations obtained by the above-mentioned tests. The model considers the characteristics of the plastic and creep deformations in cyclic loading where loading direction changes. Simulations of cyclic loading of the SAC solder under several loading conditions are conducted using the proposed model and the results are compared with experiments. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 - Proceedings of 49th AIAA Aerospace Sciences Meeting AIAA 2011-254-1-9 2011年 [査読無し][通常論文]
**High Thermal Conductive Composite Containing a Network of Vapor Grown Carbon Fiber and Carbon Nanotube in Aluminum Matrix** - 日本機械学会 2011年 [査読無し][通常論文]
**機械実用便覧** - 福地 孝平, 佐々木 克彦, 今西 輝光, 清水 昭之, 垣辻 篤 学術講演会講演論文集 59 327 -328 2010年
- 高橋 和彦, 佐々木 克彦 学術講演会講演論文集 59 199 -200 2010年
- 嶋中 和哉, 福地 孝平, 佐々木 克彦, 今西 輝光, 清水 昭之, 垣辻 篤 学術講演会講演論文集 59 329 -330 2010年
- 南 貴士, 黒田 明慈, 坂 健太郎, 佐々木 克彦 学術講演会講演論文集 59 453 -454 2010年
- Proceedings of The 7th Asian-Australasian Conference on Composite Material(ACCM-7) CD-ROM, Wed-SE27-02 2010年 [査読無し][通常論文]
**Analytical and experimental study for vibration of laminated VGCF/Al circular plate** - Tsuyoshi Takahashi, Katsuhiko Sasaki FATIGUE 2010 2 (1) 767 -776 2010年 [査読無し][通常論文]

To meet several marketing demands, development of new aluminum alloys which can be used for future high-efficiency diesel engines has been widely pursued. Especially, cylinder heads (hereafter referred to as "head(s)") are used at high combustion pressure and very high temperature, which makes it difficult to achieve a structure with light weight and high rigidity. In this study, aluminum alloy A356 (Al-Si-Mg series) which is a major head material, were conducted the thermal fatigue tests. Thus, the authors focused on the changing of material characteristics (hardness and stress-strain curves as for macroscopic characteristic and microstructure as for microscopic characteristic) during the test. This paper deals with the effects of artificial aging on two aluminum alloys A356, which have been often used for engine cylinder heads. The aluminum alloys were artificially aged under several different conditions after T6 heat treatment. The alloys were tested for fatigue characteristics as thermo-mechanical fatigue failure. The microstructure was observed by TEM to see the effects on microstructure in terms of fatigue failure. In addition, we examined the microstructure of an actual head after a durability test, and tried to find out whether material test conditions above mentioned were reasonable. Finally, the relationship between the microstructure changes and the low cycle thermal fatigue is discussed. (C) 2010 Published by Elsevier Ltd. - 中川 博史, 佐々木 克彦, 眞山 剛 北海道支部講演会講演概要集 2009 (48) 129 -130 2009年11月28日
- 古家 直明, 佐々木 克彦, 成田 吉弘 Dynamics & Design Conference 2009 "251 -1"-"251-5" 2009年08月03日Composite materials, containing carbon nanotubes or vapor-growth carbon fibers, provide excellent thermal conductivity and specific intensity, and the thermal characteristics of the materials have been studied intensively in recent years. In the present report, a method of vibration analysis is proposed to obtain natural frequencies and mode shapes of circular plates composed of VGCF and aluminum layers. The Ritz method is used to derive a frequency equation. The finite element analysis is also made to calculate frequencies of the plates for comparison, and the accuracy of the Ritz solution is established.
- 佐々木 克彦, 小林 琢爾, 眞山 剛 M&M材料力学カンファレンス 2009 741 -743 2009年07月24日For downsizing of electronic devices, flip-chip bonding method using BOA (Ball Grid Array) solder joints is widely used. It is known that there are a few crystal grains in a solder ball made of Sn-3Ag-0.5Cu, and therefore, grain orientations of BOA solder balls affect thennal defonnation of electronic packaging. In this paper, the fmite element method of the crystal plasticity is used to clarify the difference in the deformation of the solder balls due to the crystal orientations. As a result, the effect of the crystal orientations of grains on the defonriation is clarified. Moreover, bending deformation is simulated by structural analyses of electronic packaging considering the crystal orientation of the solder balls.
- 長谷川 健太, 佐々木 克彦, 成田 吉弘 バイオエンジニアリング講演会講演論文集 2008 (21) 223 -224 2009年01月22日
- 今西輝光, 片桐一彰, 佐藤豊弘, 仲摩信人, 佐藤安彦, 清水昭之, 佐々木克彦, 垣辻篤 粉体粉末冶金協会講演概要集 2009 2009年
- 佐々木 克彦, 小林 琢爾, 吉田 明生, 眞山 剛 学術講演会講演論文集 58 139 -140 2009年
- 福地 孝平, 佐々木 克彦, 今西 輝光, 片桐 一彰, 桓辻 篤 学術講演会講演論文集 58 305 -306 2009年 [査読無し][通常論文]
- 今西 輝光, 佐々木 克彦, 片桐 一彰, 垣辻 篤 日本機械学会論文集 A編 75 (749) 27 -33 2009年 [査読無し][通常論文]

In this paper, vapor-grown carbon fiver (VGCF), which is a kind of carbon nanotubes (CNT), is used for the composite materials with aluminum matrix. It is found out that the thermal conductivity of the composites is about 2.5 times higher than that of the pure aluminum of the matrix if the direction of VGCF is aligned. To improve the thermal conductivity of the composites, small amount of CNT were added to the VGCF filler. The effect of the addition of CNT on the thermal conductivity was examined by both the finite element analysis (FEM) and the measurements of the thermal conductivity. Simulations of finite element analysis (FEM) shows that the possibility to improve the thermal conductivity with small amount addition of CNT because of the cross-link (VGCF-CNT-VGCF). Therefore, small amount of CNT are added to the VGCF/aluminum composites. The thermal conductivity of the composites added CNT have about 20% higher thermal conductivity than that of the composites without CNT. The cross-links of VGCF due to the CNT addition is also confirmed by FE-SEM observation. - Transactions of JSME, Serise A 75 (749) 27 -33 2009年 [査読無し][通常論文]
**Thermal Conductivity of VGCF/Aluminum Composites With CNT Addition** - 本田 真也, 成田 吉広, 佐々木 克彦 最適化シンポジウム講演論文集 2008 (8) 185 -190 2008年11月26日A new design method is proposed here to maximize the fundamental frequency of laminated composite plates reinforced by curvilinear fibers. Spline functions represent arbitrarily shaped fibers and Ritz solutions generate frequency equations. The optimum curvilinear shapes are searched for the maximum fundamental frequencies using genetic algorithms, and the increments of data points which define the spline shape are used as design variables under the limited range of undulation. Comparison of the present analysis method gives good agreement with the finite element method in terms of natural frequencies and vibration modes, and the optimized results show that the present plate with optimally shaped curvilinear fibers gives higher or equal fundamental frequencies than those of the conventional plate with optimally oriented parallel fibers.
- 長谷川 健太, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2008 (47) 11 -12 2008年09月27日
- 吉田 明生, 佐々木 克彦, 眞山 剛, 黒田 充紀, 成田 吉弘 M&M材料力学カンファレンス 2008 "OS0601 -1"-"OS0601-2" 2008年09月16日Sn-Ag系の鉛フリーはんだを用いたBGA (Ball Grid Array)接続部内部の結晶粒数は,数個であることが知られており,BGAの変形に対し結晶方位が大きく影響を与えると考えられる.そこで,本研究ではSn-3Ag-0.5CuのBGAはんだの結晶塑性モデルを用い,結品粒数や結晶方位などの条件を変え,BGAにせん断変形が加えられた時の応力,ひずみ分布について検討した.その結果,BGA内部の応力・ひずみ分布は結晶方位の影響を大きく受けること,結晶界面には結晶方位の違いにより特異の応力分布となることを明らかにした.
- 青木 亮爾, 申 義燮, 成田 吉弘, 佐々木 克彦 Dynamics & Design Conference 2008 "167 -1"-"167-6" 2008年09月02日A method of analysis is presented for determining the free vibration frequencies of twisted laminated panels under general edge conditions, and is implemented in a layerwise optimization (LO) scheme to determine the optimum fiber orientation angles for the maximum fundamental frequency. Based on the classical lamination theory, a method of Ritz is used to derive a frequency equation where in the displacement functions are modified to accommodate arbitrary sets of edge conditions for both in-plane and out-of-plane motions. In numerical examples, natural frequencies and mode shapes are presented for a wide range of geometric parameters, and the maximum fundamental frequencies are determined by the LO design approach.
- 加藤 大翔, 成田 大祐, 成田 吉弘, 佐々木 克彦 Dynamics & Design Conference 2008 "153 -1"-"153-6" 2008年09月02日This study proposes an optimization method to deal with free vibration of shallow shells with generally curved surfaces expressed in terms of cubic polynomial functions. Such shell structures with variable curvature are recently found in automobile and other design-oriented structural applications. In the first example, the fundamental frequency is maximized as the object function with respect to the curvature. The second example is given to maximize the difference of the lowest two frequencies, and the third one is to find the best curvature design to fit to any desired vibration frequency within the physically possible range. The optimization technique employed here is a part of functions in ADS program that is based on mathematical programming.
- 大渡 康介, 申 義燮, 成田 吉弘, 佐々木 克彦 Dynamics & Design Conference 2008 "166 -1"-"166-6" 2008年09月02日The fundamental frequencies of symmetrically laminated composite plates with irregular shapes are maximized with respect to fiber orientation angles in the layers. Based on the first-order shear deformation theory (FSDT), the eight-node quadrilateral isoparametric element is developed, and a layerwise optimization (LO) approach is extended to be combined with this finite element. In numerical examples, trapezoidal plates with different side ratios and square plates with different position of circular holes are analyzed for six different boundary conditions. Finally, the significant effects of different shapes on the maximized fundamental frequencies and the best fiber orientation are demonstrated.
- 矢澤 宗厚, 成田 吉弘, 佐々木 克彦 Dynamics & Design Conference 2008 "351 -1"-"351-6" 2008年09月02日Drink bottle shapes are considered in this study from the viewpoint of Kansei engineering. Nine different bottle models, that imitate PET bottles widely used for soft drinks, were fabricated and are used in the test. The impressions over the bottle model surfaces are targeted by surveying and collecting human reactions on the twelve sets of word (adjective) pairs from examinees. After applying some statistical treatments, such as the semantic differential and factor analysis methods, the general tendency of human emotional reactions to the bottle shapes are discussed.
- 佐々木 克彦, 今西 輝光, 片桐 一彰, 浅野 佑介, 垣辻 篤 学術講演会講演論文集 57 271 -272 2008年 [査読無し][通常論文]
- 日本機械学会論文集（A編） 74 655 -661 2008年 [査読無し][通常論文]
**CNTを添加したVGCF/アルミニウム複合材料の熱伝導特性** - JSAE Transaction 39 (1) 113 -120 2008年 [査読無し][通常論文]
**The Change of Microstructure and Material Behavior of Aluminum Alloy of Cylinder Head** - Transactions of JSME, Serise A 74 655 -661 2008年 [査読無し][通常論文]
**Thermal Conductivity and Stength of Aluminum Composites Containing VGCF** - 佐々木 克彦 塑性と加工 = JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY 48 (561) 916 -917 2007年10月25日
- 吉田 明生, 小林 琢爾, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2007 (46) 67 -68 2007年09月29日
- 高橋 剛, 佐々木 克彦, 豊田 武司, 飯田 真 北海道支部講演会講演概要集 2007 (46) 115 -116 2007年09月29日
- 眞山 剛, 黒田 充紀, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2007 (46) 53 -54 2007年09月29日
- 本田 真也, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2007 (46) 105 -106 2007年09月29日
- 金井 俊起, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2007 (46) 43 -44 2007年09月29日
- 村山 健一, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2007 (46) 31 -32 2007年09月29日
- 眞山剛, 大橋 鉄也, 佐々木 克彦, 成田 吉弘 機講論 7 715 -716 2007年
- Katsuhiko Sasaki, Takuji Kobayashi, Ken-ichi Ohguchi IPACK 2007: PROCEEDINGS OF THE ASME INTERPACK CONFERENCE 2007, VOL 2 99 -105 2007年 [査読無し][通常論文]

Ratchetting deformations of solder alloys are significant deformations for the safety and reliability of solder joints of electronic packaging. In this paper, the microstructural change of the solder alloys due to the uniaxial ratchetting deformation is evaluated to clarify the effect of the microstructure on the viscous deformation of solder alloys. The microstructures are observed after the specimens are subjected to the uniaxial ratchetting deformation during several cycle numbers. The change of the size of grains or lamella structures is used to evaluate the uniaxial ratchetting deformation of solder alloys. The observation clarifies that the differences in the microstructural change due to the uniaxial ratchetting deformation between the lead-free and lead-containing solder alloys. The uniaxial ratchetting deformation and the additional creep deformation after the ratchetting deformation is also simulated by the dislocation based constitutive model. The simulation suggests that the material parameters used in the constitutive model may be correlated to the microstructural change of the solder alloys. - Ken-ichi Ohguchi, Katsuhiko Sasaki, Setsuo Aso IPACK 2007: PROCEEDINGS OF THE ASME INTERPACK CONFERENCE 2007, VOL 2 107 -113 2007年 [査読無し][通常論文]

This paper proposes a method which can estimate essential material constants of an elasto-plastic-creep constitutive model for lead-free solders by conducting only a tensile test. The test employs a stepped ramp wave loading which repeats instantaneous straining and strain maintaining. The time-independent strains can be evaluated by using the stress-strain relations at the instantaneous straining parts, while the time-dependent strain can be evaluated by using the stress-time relations during the strain maintaining parts. Based on the results of the evaluations, the material constants of the elasto-plastic-creep models are estimated. Simulations of the viscoplastic deformations of Sn-3.0Ag-0.5Cu solder alloy were also conducted to verify the validity of the proposed method. - 本田 真也, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2006 (45) 105 -106 2006年09月25日
- 小林 琢爾, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2006 (45) 113 -114 2006年09月25日
- 高橋 剛, 佐々木 克彦, 豊田 武司, 飯田 真 北海道支部講演会講演概要集 2006 (45) 91 -92 2006年09月25日
- 眞山 剛, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2006 (45) 115 -116 2006年09月25日
- 村山 健一, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2006 (45) 107 -108 2006年09月25日
- 川上 琢麿, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2006 (45) 143 -144 2006年09月25日
- 佐々木克彦, 片桐一彰, 垣辻篤, 佐藤豊弘, 今西輝光, 仲摩信人, 清水昭之 FRPシンポジウム講演論文集 35th 2006年
- 眞山 剛, 中田 光洋, 佐々木 克彦, 成田 吉弘 学術講演会講演論文集 55 403 -404 2006年
- 眞山 剛, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2005 (44) 34 -35 2005年10月08日In this study, material parameters of inelastic constitutive model are identified by using the steepest decent method (SDM) and random search (RS). For parameter identification the difference between the experimental results and the simulated data is minimized. Both of the two methods show good adaptability for cyclic plasticity experiment of pure titanium. A random number generator including multi-pseudo-random number generators is used in RS and the dependency of number of pseudo-random number generators is confirmed.
- 小林 琢爾, 佐々木 克彦, 成田 吉弘 北海道支部講演会講演概要集 2005 (44) 32 -33 2005年10月08日
- 中田 光洋, 佐々木 克彦, 成田 吉弘, 眞山 剛 北海道支部講演会講演概要集 2005 (44) 10 -11 2005年10月08日
- 菊池 真, 成田 吉弘, 佐々木 克彦 北海道支部講演会講演概要集 2005 (44) 166 -167 2005年10月08日
- 眞山 剛, 魚原 進吾, 佐々木 克彦, 成田 吉弘 設計工学・システム部門講演会講演論文集 2005 (15) 88 -89 2005年08月02日A numerical method is proposed for deformation analysis of the balloon-expandable stents. An inelastic constitutive model is made from the experimental data of tension-compression tests and is incorporated into the commercial FEM code (MSC Marc/Mentat) to realize accurate prediction. Simulation study is made for the expanding behaviors of the stent made of SUS316L or pure titanium with a balloon mounted inside, and the effects of using different materials are discussed on the mechanical characteristics of the stents.
- 眞山 剛, 佐々木 克彦, 成田 吉弘 学術講演会講演論文集 54 361 -362 2005年
- 2005年 [査読無し][通常論文]
**Honda,S., Narita,Y., and Sasaki,K.:"Discrete Optimization for Vibration Design of Composite Plates by Using Lamination Parameters", Proceedings of International Conference for Mechanical and Automotive Technologies:171-76( 2005)** - 2005年 [査読無し][通常論文]
**Mayama,T., Sasaki,K., and Narita,Y.:"Effects of Cyclic Plasticity Induced Meso-Structures on Subsequent Viscoplastic Deformations", Proceedings of International Conference for Mechanical and Automotive Technologies:267-271(2005)** - 2005年 [査読無し][通常論文]
**Ohguchi,K. and Sasaki,K.:"A Viscoplastic Constitutive Model and Estimation Method of Material Constants for Lead-Free Solder Alloys", Proceedings of ASME InterPACK'05[(CD-ROM)No. IPACK2005-73103](2005)*** - 2005年 [査読無し][通常論文]
**Toda,Y., Sasaki,K., Narita,Y., Katagiri,K., Satoh,T., Imanishi,T., Nakama,N., and Kaketsuji,A.:"Mechanical Properties of Carbon Nanotube-Containing Aluminum Materials", Proceedings of International Conference for Mechanical and Automotive Technologies:・・・**

Toda,Y., Sasaki,K., Narita,Y., Katagiri,K., Satoh,T., Imanishi,T., Nakama,N., and Kaketsuji,A.:"Mechanical Properties of Carbon Nanotube-Containing Aluminum Materials", Proceedings of International Conference for Mechanical and Automotive Technologies:71-75(2005) - 2005年 [査読無し][通常論文]
**Sasaki,K., Takahashi,T.:"Artificial Aging Effect on Strength and Fatigue Failure of an Aluminum Alloy for Engines”, Proceedings of International Conference for Mechanical and Automotive Technologies:65-69(2005)** - 2005年 [査読無し][通常論文]
**Sasaki,K., Ohguchi,K., and Kobayashi,T:"Correlation between Creep and Uniaxial Ratchetting of Sn/37Pb and Sn/3Ag/0.5Cu Solder Alloys", Proceedings of ASME InterPACK'05[(CD-ROM)No. IPACK2005-73054](2005)*** - 2005年 [査読無し][通常論文]
**Kobayashi,T., Sasaki,K., and Narita,Y.:"Viscoplastic Deformation of Sn/37Pb and Sn/3Ag/0.5Cu Solder Alloys", Proceedings of International Conference for Mechanical and Automotive Technologies:263-266(2005)** - 材料力学 2005年 [査読無し][通常論文]
**機械工学便覧,基礎編α３<日本機械学会編（分担執筆）>** - 眞山 剛, 佐々木 克彦, 成田 吉弘 計算力学講演会講演論文集 2004 (17) 725 -726 2004年11月17日
- 大口 健一, 佐々木 克彦, 石橋 正博 計算力学講演会講演論文集 2004 (17) 785 -786 2004年11月17日
- 日本材料学会 2004年 [査読無し][通常論文]
**はんだのクリープ試験法標準** - 日本材料学会 2004年 [査読無し][通常論文]
**はんだのクリープ疲労試験法標準** - 眞山 剛, 佐々木 克彦 計算力学講演会講演論文集 2003 (16) 547 -548 2003年11月22日
- 眞山 剛, 佐々木 克彦 北海道支部講演会講演概要集 2003 (43) 24 -25 2003年09月28日
- Ohguchi Ken-ichi, Sasaki Katsuhiko Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003 (2) "OS10W0188 -1"-"OS10W0188-6" 2003年09月10日In this paper, a viscoplastic constitutive model was proposed considering both the determination method of the material constants and the implementation method for a general purpose FEM program. The model was incorporated into FEM code "ANSYS" and its applicability to the lead-free solder alloys was verified by the simulations of the viscoplastic deformation. As a result, the proposed model was successfully incorporated into "ANSYS", and then it could accurately describe the creep and cyclic loading of three lead-free solder alloys using the material constants determined from only the pure tensile tests.
- Mayama Tsuyoshi, Sasaki Katsuhiko, Ishikawa Hiromasa Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003 (2) "GSW0044 -1"-"GSW0044-6" 2003年09月10日In this study, the interaction between plasticity and creep deformation is observed from both macro and microscopic point of view using Type 304 stainless steel at room temperature. The experiments conducted in this study are as follows: (1) subsequent creep after tension-compression cyclic preloading with a constant strain amplitude under a constant strain rate; (2) subsequent torsional creep after cyclic torsional preloading with a constant strain amplitude under a constant strain rate; (3) subsequent stress relaxation tests after tension-compression cyclic preloading with a constant strain amplitude under a constant strain rate; (4) tension-compression cyclic loading with the change of the strain rate. These experimental results show that the subsequent time-dependent deformations are depending on the number of cycles of the preloading even though the stress-strain curves of the preloading are almost same. To verify the difference from microscopic point of view transmission electron microscope (TEM) observations are conducted. The dislocation structures observed are clearly different due to the number of cycle of the preloading.
- 眞山 剛, 佐々木 克彦, 石川 博將 学術講演会講演論文集 52 117 -118 2003年
- 佐々木 克彦, 眞山 剛, 石川 博將 計算力学講演会講演論文集 2002 (15) 131 -132 2002年10月30日
- 眞山 剛, 佐々木 克彦, 石川 博將 北海道支部講演会講演概要集 2002 (42) 148 -149 2002年10月05日In this study, a series of tests such as cyclic tension-compression loading with the constant strain amplitude under the constant strain rate and creep tests are carried out at high temperature by using oxygen-free copper (OFC) A cyclic loading tension-compression tests under variations of temperature is also conducted. The experimental results show that the temperature history does not affect stress-strain relations under cyclic tension-compression loading regardless of variations of temperature. Using the material constants determined by the cyclic tension-compression test at isothermal condition, creep and cyclic deformations under variations of temperature can be well simulated by the viscoplastic model.
- 柳本 陽征, 石川 博將, 佐々木 克彦 北海道支部講演会講演概要集 2002 (42) 144 -145 2002年10月05日In this paper, to clarify behavior of bending of electronic devices dur to tmperature change during a reflow process, basic experiments and simulations are carried out using lead solder alloy (Sn-379Pb) and lead free solder alloy (Sn-3.5Ag-0.75Cu). The pure tension, creep, and stress relaxation tests are performed as the basic experiments. Also FEM analysis is conducted using a viscoplastic constitutive model into which the concept of dislocation density is incorporated. Finally the difference of the bending process of lead and lead free solder alloys is clarified.
- 高橋 剛, 佐々木 克彦, 石川 博将, 杉村 良男 北海道支部講演会講演概要集 2002 (42) 146 -147 2002年10月05日
- 渡邉 祐輔, 佐々木 克彦, 石川 博將, 眞山 剛 北海道支部講演会講演概要集 2002 (42) 196 -197 2002年10月05日Is this paper, development of slip bands during plastic deformation is observed by pure tensile tests with specimens made of tough pitch copper. The slip are microscopically observed at several strain range during the tensile loading. The microscopical observation shows that the number of the slip bands increases with increase in the strain range. The stress-strain relations caused by the pure tension are also simulated by a constitutive model based on dislocation density. Finally, the correlation between the number of slip bands and the dislocation density simulated by the model is discussed.
- 2002年 [査読無し][通常論文]
**Takahashi, T., Sasaki, K., Nagayoshi, T., Tsujimura, A.:“Thermal Plastic-Elastic Creep Analysis of Engine Cylinder Head”, SAE2002 World Congress & Exposition, Paper No. 2002-01-0585 (2002)*** - 2002年 [査読無し][通常論文]
**Takahashi, T., Moizumi, K., Iida, M., Sasaki, K.：“Effect of Thermal Fatigue Phenomena of Aluminum Alloy by Artificial Ageing”, SAE2002 World Congress & Exposition, Paper No. 2002-01-0584 (2002)*** - 佐々木 克彦, 石川 博將 計算力学講演会講演論文集 2001 (14) 81 -82 2001年11月27日
- 大口 健一, 野々山 裕芝, 佐々木 克彦, 田上 道弘 計算力学講演会講演論文集 2001 (14) 495 -496 2001年11月27日
- 柳本 陽征, 石川 博將, 佐々木 克彦 計算力学講演会講演論文集 2001 (14) 497 -498 2001年11月27日In this paper, viscoplastic constitutive model for deformation of Pb free solder alloys was proposed. FEM analysises of microelectronics solder joints was also conducted using the viscoplastic constitutive model. For the FEM analysis, basic experiments, such as pure tension, cyclic loading and creep tests were conducted using Sn-3.5Ag-0.75Cu solder alloy at several tests conditions. As a result, it was found that the thermal deformation of the solder alloy was successfully simulated by the FEM analysis, into which the constitutive model was incorporated.
- 大口 健一, 佐々木 克彦 計算力学講演会講演論文集 2001 (14) 493 -494 2001年11月27日
- 佐々木 克彦, 柳本 陽征, 石川 博將 機械材料・材料加工技術講演会講演論文集 2001 (9) 193 -194 2001年11月02日This paper treats experimental observation on mechanical behavior such as viscoplastic deformation of both Pb and Pb free solder alloys. The tests conducted in this work are pure tension, cyclic tension-compression loading, creep and stress relaxation. The test results show that the Pb solder alloy has larger time dependent deformation comparing with Pb free solder alloys. The stress relaxation of the Pb solder alloys is, especially, larger than that of the Pb free solder alloy. The smaller stress relaxation of the Pb free solder alloy leads to bending of the substrate. The method to simulate the deformation of Pb free solder alloys is also discussed.
- 眞山 剛, 佐々木 克彦, 石川 博將 機械材料・材料加工技術講演会講演論文集 2001 (9) 287 -288 2001年11月02日In this study, a series of biaxial ratchetting tests and numerical simulations are carried out. Experimental results obtained on SUS304 stainless steel subjected to biaxial ratchetting showed the dependence of superposed stress and the dependence of direction of load. Moreover biaxial ratchetting superposed zero stress induced steady ratchetting strain in tensile direction. Finally a unified constitutive equation was used for computer simulation. The simulation could describe characteristic features of biaxial ratchetting.
- 柳本 陽征, 石川 博將, 佐々木 克彦 北海道支部講演会講演概要集 2001 (41) 26 -27 2001年09月25日In this paper, viscoplastic constitutive model for deformation of Pb free solder alloys was proposed. FEM analysises of microelectronics solder joints was also conducted using the viscoplastic constitutive model. For the FEM analysis, basic experiments, such as pure tension, cyclic loading and creep tests were conducted using Sn-3.5Ag-0.75Cu solder alloy at several tests conditions. As a result, it was found that the thermal deformation of the solder alloy was successfully simulated by the FEM analysis, into which the constitutive model was incorporated.
- 眞山 剛, 佐々木 克彦, 石川 博將 北海道支部講演会講演概要集 2001 (41) 4 -5 2001年09月25日In this study, a series of experiments and numerical simulations are carried out. Experimental results obtained on SUS304 stainless steel subjected to biaxial ratchetting showed the dependence of strain amplitude and the dependence of strain rate. A unified constitutive equation was used for computer simulation. The simulation could describe characteristic features of biaxial ratchetting.
- 眞山 剛, 佐々木 克彦, 石川 博將 学術講演会講演論文集 50 31 -32 2001年
- 2001年 [査読無し][通常論文]
**H. Ishikawa, K. Sasaki and T. Mayama,“Equivalence of Back Stress during Plastic and Creep Deformation”:391-400 (S. Murakami & N. Ohno eds.:IUTAM Symposium on Creep in Structure, Kluwer Academic Publishers, USA), (2001).** - 2001年 [査読無し][通常論文]
**H. Ishikawa and K. Sasaki,“Section 4.7 Kinematic Hardening Rule for Biaxial Ratcheting”(J. Lemaitre eds.:Handbook of Materials Behavior Models, Academic Press, USA)(2001).** - 2001年 [査読無し][通常論文]
**K. Sasaki, K. Ohguchi, A. Yanagimoto, H. Ishikawa, “Viscoplastic Deformation of Sn-3.5Ag-0.75Cu Solder Alloys,” Material Science Research International, Special Technical Publication, 2: 397-402 (2001).** - 柳本 陽征, 石川 博將, 佐々木 克彦 北海道支部講演会講演概要集 2000 (40) 6 -7 2000年09月25日In this paper, FEM analysises of microelectronics solder joints subjected to cyclic thermal deformation were conducted. Pb free solder alloys (Sn-3.5Ag-0.75Cu) were chosen for the analysis, because of the regulation of using Pb/Sn solder alloys in near future. Results of Pb free solder alloys were compared with that of Pb/Sn solder alloys. Elasto-plastic, elasto-creep, and elasto-plastic-creep analysis were employed in this paper. As a result, it was found that the equivalent stress of Sn-3.5Ag-0.75Cu is much larger than that of Pb/Sn solder alloys, and that the elasto-plastic-creep analysis takes advantage of the simulation both of Pb free and Pb/Sn solder alloys.
- 眞山 剛, 佐々木 克彦, 石川 博將 学術講演会講演論文集 49 347 -348 2000年
- 佐々木 克彦, 石川 博將 学術講演会講演論文集 49 351 -352 2000年
- 瓜生 淳一, 佐々木 克彦, 石川 博將, 大口 健一 学術講演会講演論文集 49 437 -438 2000年
- 2000年 [査読無し][通常論文]
**Sasaki, K. and Ishikawa, H.:"Simulation of Ratchetting Behavior Using Constitutive Model Based on Dislocation Density",Plastic and Viscoplastic Response of Materials and Metal Forming, 1:372-374 (2000)** - 2000年 [査読無し][通常論文]
**Ohguchi, K. Sasaki K. and Ishikawa H.:"Constitutive Modeling for Sn-3.5Ag-0.75Cu Solder Alloys", Plastic and Viscoplastic Response of Materials and Metal Forming,1: 366-368 (2000)** - 高橋 剛, 佐々木 克彦 いすず技報 (101) 62 -70 1999年06月
- 1999年 [査読無し][通常論文]
**Ishikawa, H., and Sasaki K.:"Constitutive Model of Plasticity for Finite Deformation",Proceedings Asia Pacific Conference for Fracture and Strength, 【1/1(CD-ROM) SM0-1-SM0-6】 (1999).** - 1999年 [査読無し][通常論文]
**Sasaki, K., and Ishikawa, H.:"Correlation Between Uniaxial Ratchetting and Viscous Deformation - Observation Using Dislocation Based Constitutive Model -", Proceedings Asia Pacific Conference for Fracture and Strength, 【1/1(CD-ROM) SM8-1-SM8-6】 (1999).** - 1999年 [査読無し][通常論文]
**Ohguchi K., Sasaki K. and Ishikawa H.:"Fatigue Life and Its Estimation for Pb/Sn Solder Alloy", Proceedings Asia Pacific Conference for Fracture and Strength, 【1/1(CD-ROM) PK01-1-PK01-6】 (1999).** - 1999年 [査読無し][通常論文]
**Sasaki, K. and Ishikawa, H.:"Observation on Interaction Between Ratchetting and Creep Deformation for Constitutive Modeling", Proceedings of Fifth International Conference on Constitutive Laws for Engineering Materials, 1:139-142 (1999).** - Tsuyoshi Takahashi, Asao Koike, Katsuhiko Sasaki SAE Technical Papers 1998年 [査読無し][通常論文]

Many methods for estimating the fatigue life of an aluminum alloy have been proposed in order to save development time and cost as demand for durable and light-weighted material grows strong. None of them, however, are practical enough to estimate the life of an engine component because thermal and mechanical loads on the engine component change as time elapses. Firstly, this paper deals with a method for clarifying the inelastic characteristics of an aluminum alloy, especially the effects of strain amplitude, ductile period (compression-tension cycle time) and temperature range on inelastic deformation, by making experiment where both thermal and mechanical loads were applied in the inverted phase('out-of phase'). Secondly the paper discusses a possibility of improving accuracy in determining the fatigue life of the material by introducing a new index of 'plastic work density per second', which is based on the conventional concept of plastic strain energy density. Copyright © 1998 Society of Automotive Engineers, Inc. - 佐々木 克彦, 高橋 剛, 石川 博將, 小池 朝夫 学術講演会講演論文集 46 177 -178 1997年
- 佐々木 克彦, 石川 博將 学術講演会講演論文集 43 71 -72 1994年
- 佐々木 克彦 日本林学会北海道支部論文集 (36) 140 -142 1988年03月01日
- 佐々木 克彦 日本林学会北海道支部論文集 (35) 68 -70 1987年03月10日

- 佐々木 克彦他
**特願2015-179760:鋼の熱処理シミュレーション方法および鋼の熱処理シミュレーションプログラム**2018年04月12日 - 片桐一彰, 佐々木克彦, 垣辻篤
**特願5569839:炭素繊維配向シート製造方法**2014年11月 - 佐々木克彦
**特願5288441:高熱伝導複合材料とその製造方法**2013年09月11日

- 2016年 日本機械学会機械材料・材料加工部門 部門一般表彰（優秀講演論文部門）

受賞者: 佐々木 克彦 - 2008年 日本機械学会機械材料・材料加工部門 部門一般表彰（優秀講演論文部門）
- 1996年04月 日本機械学会 日本機械学会賞 研究奨励賞

受賞者: 佐々木 克彦 - 1992年12月 米国機械学会 米国機械学会冬季講演会優秀論文賞(米国機械学会電子パッケージ部門)

受賞者: 佐々木 克彦

**塑性変形の局所化を考慮した最適設計によるカスタムメードステントの開発**天田財団：研究助成研究期間 : 2018年11月 -2020年03月代表者 : 佐々木 克彦**金属焼結３Dプリンターによるカスタムメードステントの開発**御器谷科学技術財団：研究助成研究期間 : 2018年04月 -2019年03月代表者 : 佐々木 克彦**要素レベル解析のFEM適用検証およびはんだ試験データ取得**三菱電機株式会社：共同研究研究期間 : 2013年04月 -2018年03月代表者 : 佐々木 克彦**塑性変形不均一構造を取り入れたカスタムメード・ステントの開発**天田財団：研究助成研究期間 : 2015年12月 -2017年03月代表者 : 佐々木 克彦**血管へのダメージの少ないバルーン拡張ステントの最適構造設計**日本学術振興会：科学研究費補助金研究期間 : 2014年04月 -2017年03月代表者 : 佐々木 克彦**携帯電話の熱拡散構造および振動制御構造の研究｣**富士通株式会社：共同研究研究期間 : 2013年04月 -2015年03月代表者 : 佐々木 克彦**金属中に均一に分散する技術の開発**技術研究組合 単層ＣＮＴ融合新材料研究開発機構：共同研究研究期間 : 2010年04月 -2015年03月代表者 : 佐々木 克彦**カーボンナノチューブ複合材料の開発**住友精密株式会社：共同研究研究期間 : 2003年08月 -2010年03月代表者 : 佐々木 克彦**超高密度電子実装基板の等価複合モデルによる最適構造解析**電子回路基板技術振興財団：研究助成研究期間 : 2007年04月 -2008年03月代表者 : 佐々木 克彦**純チタンの微視的組織変化を考慮したマイクロステントの変形解析**日本学術振興会：科学研究補助金研究期間 : 2005年04月 -2007年03月代表者 : 佐々木 克彦- 研究期間 : 2005年
**Microstructural Change of Stent due to Expansion** **Thermal and Mechanical Properties of CNT Composite Materials**Cooperative Research研究期間 : 2004年**電子デバイス接続部の鉛フリー化のための変形制御構成モデルに関する研究**日本学術振興会：科学研究費補助金研究期間 : 2000年04月 -2002年03月代表者 : 佐々木 克彦**表面張力を利用した3次元マイクロ構造物の力学特性に関する研究**文部省：科学研究補助金研究期間 : 1998年04月 -2000年03月代表者 : 佐々木 克彦**Thermal and Mechanical Deformation of Multi-Layered Electronic Packaging**Cooperative Research研究期間 : 1999年**複合負荷を受ける先進複合材料のダメージと巨視的力学特性の相互関係に関する研究**文部省：科学研究補助金研究期間 : 1995年04月 -1996年03月代表者 : 佐々木 克彦**ラチェットと塑性変形の相互作用に関する研究**文部省：科学研究補助金研究期間 : 1992年04月 -1993年03月代表者 : 佐々木 克彦**クリープと塑性変形の相互作用に関する研究**文部省：科学研究費補助金研究期間 : 1991年04月 -1992年03月代表者 : 佐々木 克彦**Viscoplastic Constitutive Model for Bio and Electronic Materials Considering Micro Structural Change**Cooperative Research研究期間 : 1989年

- メディカルデバイス・マテリアル特論開講年度 : 2021年課程区分 : 修士課程開講学部 : 工学院キーワード : 医療器械、生体材料、機械工学、材料力学、粘弾性材料
- 人間機械システムデザイン特別演習開講年度 : 2021年課程区分 : 修士課程開講学部 : 工学院
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