論文 - 上森　武

Crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading

Takeshi UEMORI, Naoya TADA, Junji SAKAMOTO

Mechanical Engineering Journal   12 ( 2 )   24 - 00340   2025年

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Society of Mechanical Engineers  

DOI： 10.1299/mej.24-00340

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Effect of artificial defect on tensile properties of thin titanium alloy wire 査読

Junji SAKAMOTO, Naoya TADA, Takeshi UEMORI, Koyo OISHI

Extended abstract of The Advanced Technology in Experimental Mechanics and International DIC Society Joint Conference 2023 (ATEM-iDICs '23)   11 ( 6 )   24-00129   2024年12月

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

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荷重制御疲労試験時のTi-6Al-4V細線の破壞形態

坂本惇司, 多田直哉, 上森武

チタン   72 ( 3 )   39 - 43   2024年12月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation 査読

Naoya Tada, Hiroaki Ohashi, Takeshi Uemori, Junji Sakamoto

Journal of Physics: Conference Series   2892   012002   2024年11月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1088/1742-6596/2892/1/012002

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Crystal plasticity analysis of fatigue crack initiation site considering crystallographic orientation in Ti–22V–4Al alloy

Jinta Arakawa, Koki Hirazumi, Takeshi Uemori, Yoshito Takemoto

Results in Engineering   23   2024年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.rineng.2024.102405

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Method for Predicting Crack Size Using Amplitude Change in Titanium Alloy under Bending Vibration 査読

坂本惇司, 多田直哉, 上森武

Book of Abstracts: Europian Conference on Fracture 2024 (ECF24)   472   2024年9月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Elucidation of small fatigue crack initiation and propagation behavior on polycrystal Ti-22V-4Al 査読

Jinta Arakawa, Koki Hirazumi, Takeshi Uemori, Yoshito Takemoto

Procedia Structural Integrity   66   38 - 48   2024年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.prostr.2024.11.053.

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アルミニウム合金の曲げ振動下の振動変化とき裂進展

坂本 惇司, 多田 直哉, 上森 武

日本機械学会論文集   90 ( 930 )   23-00246 - 23-00246   2024年

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記述言語：日本語   出版者・発行元：一般社団法人 日本機械学会  

DOI： 10.1299/transjsme.23-00246

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セルロースナノファイバー強化天然ゴムの繰返し引張特性と膨潤試験から得られるバウンドラバー体積分率の関係

奥井 健斗, 多田 直哉, 上森 武, 坂本 惇司, 榊原 圭太

日本機械学会論文集   90 ( 932 )   24-00008 - 24-00008   2024年

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記述言語：日本語   出版者・発行元：一般社団法人 日本機械学会  

DOI： 10.1299/transjsme.24-00008

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Prediction of active slip system for commercially pure titanium sheet by crystal plasticity finite element analysis 査読

Takeshi UEMORI, Naoya TADA, Junji SAKAMOTO, Masatoshi DOI

Extended abstract of The Advanced Technology in Experimental Mechanics and International DIC Society Joint Conference 2023 (ATEM-iDICs '23)   19-G05   2023年10月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Prediction of slip activity of crystal grains around semi-circular and semi-elliptical notches in thin-sheet specimens of pure titanium using formulated macroscopic stress distribution and crystal orientation

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Engineering Failure Analysis   107623 - 107623   2023年9月

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.engfailanal.2023.107623

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Effect of Surface Roughness and Oxidation Treatment on Joint Strength between Aluminum Alloy and High-Density Polyethylene 査読

Naoya TADA, Takeshi UEMORI, Junji SAKAMOTO

2023年8月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Tensile properties and slip deformation behavior of pure titanium thin wire with a small diameter-to-grain-size ratio

Junji Sakamoto, Naoya Tada, Takeshi Uemori

Materials Science and Engineering A   863   2023年1月

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掲載種別：研究論文（学術雑誌）  

To investigate the tensile properties and slip deformation behavior of pure titanium thin wires with a small ratio of the diameter to the grain size, tensile tests and a stepwise tensile test were performed using specimens with a diameter of approximately 170 μm and grain sizes of 17 and 87 μm, corresponding to diameter-to-grain-size ratios of 10 and ∼2, respectively. The specimen with a diameter-to-grain-size ratio of 10 fractured through the growth of voids. The fracture morphology was similar to that of the bulk specimens. On the other hand, for specimens with a diameter-to-grain-size ratio of 2, fracture occurs owing to the local deformation, in which primary slip systems are activated in each grain. The stepwise tensile test of the specimen with a diameter-to-grain-size ratio of 2 indicated that the slip deformation tended to occur from the large grains. Moreover, the activities of the slip systems of grains were evaluated using the Schmid factor (SF) and critical resolved shear stress (CRSS) of each slip system. It was noted that slip systems with the highest SF∙CRSS−1 were activated for 30 out of 33 grains.

DOI： 10.1016/j.msea.2022.144532

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Slip Activity of Crystal Grains around Notch in Thin Sheet Specimen of Pure Titanium

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Books of abstracts, 17th Asia-Pacific Conference on Fracture and Strength and 13th Conference on Structural Integrity and Failure   19 - 19   2022年12月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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複素数階微分法の純チタン板材の結晶塑性解析への適用 査読

上森武, 多田直哉, 坂本惇司

チタン   70 ( 2 )   158 - 163   2022年4月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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Effect of resin lamination on tensile strength characteristics of SUS304 stainless steel thin film 査読

Junji Sakamoto, Naoya Tada, Takeshi Uemori

International Journal of Advanced Manufacturing Technology   116 ( 3-4 )   1081 - 1088   2021年10月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The objective of this study is to clarify the effect of resin lamination on the tensile strength characteristics of SUS304 stainless steel thin films. We conducted tensile and stepwise tensile tests using several types of specimens prepared with 20-μm- and 40-μm-thick SUS304 films, 25-μm-thick polypropylene (PP) film, and 6-μm-thick polyethylene terephthalate (PET) film. Their macroscopic and microscopic tensile deformation behaviors were observed using an optical microscope and a reflection-configured digital holographic microscope, respectively. As a result, laminating the PP or PET films onto the SUS film did not significantly change the macroscopic and microscopic strain changes against the tensile load or microscopic surface changes in the low-strain region. Laminating the PET film onto the SUS film did not reduce the fracture strain, whereas laminating the PP film onto the SUS film did reduce it. One of the reasons may be that burrs formed on the side surface of the PP/SUS laminate. Polishing the side surface of the PP/SUS laminate may suppress the reduction in its fracture strain. The reduction of the fracture strain due to the PP lamination in the 20 μm thick SUS film was larger than that of the 40-μm-thick SUS film. In thin SUS films, small stress concentrators that have almost no effect on macroscopic and microscopic deformation might significantly reduce the fracture strain.

DOI： 10.1007/s00170-021-07510-8

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Prediction of the fracture location by tensile tests of gray cast iron based on the dimensional changes of graphite flakes 査読

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Journal of Pressure Vessel Technology, Transactions of the ASME   143 ( 2 )   2021年4月

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掲載種別：研究論文（学術雑誌）  

© 2021 American Society of Mechanical Engineers (ASME). All rights reserved. Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high performance-To-cost ratio. On the other hand, weak graphite flakes present in gray cast iron serve as stress concentrators and adversely affect the material strength. Therefore, it is crucial to examine the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, tensile tests on gray cast iron were carried out using a plate specimen and observed by scanning electron microscopy, and the microscopic deformation was observed on the specimen surface. Particularly, the change in the size of graphite flakes during the tensile tests was examined, and the observed trend was discussed. The experimental results reveal that the dimensional changes in the graphite flakes vary in the observed area and that the final fracture occurs in an area where a large dimensional change is observed, suggesting that the fracture location or critical parts of gray cast iron can be predicted from the dimensional changes of the graphite flakes at an early stage of deformation.

DOI： 10.1115/1.4048063

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Effect of Mechanical Surface Treatment and Post-treatment Polishing on Tensile Strength and Fatigue Life of High-speed Tool Steel 査読

N.Karunathilaka, N.Tada, T.Uemori, J.Sakamoto, R.Hanamitsu, M.Fujii, Y.Omiya, M.Kawano

International Journal of Peening Science and Technology   2 ( 1 )   35 - 60   2021年

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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Finite Element Study of the Effect of Internal Cracks on Surface Profile Change due to Low Loading of Turbine Blade 査読

Junji Sakamoto, Naoya Tada, Takeshi Uemori, Hayato Kuniyasu

Applied Sciences   10 ( 14 )   4883 - 4883   2020年7月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties of the material were detected before and after the load using a digital holographic microscope and a digital height correlation method. In this study, this technique was applied in combination with finite element analysis using a 2D and 3D model simulating the turbine blades. Analysis clarified that the change in the surface properties under a small load varied according to the presence or absence of a crack, and elucidated the strain distribution that caused the difference in the change. In addition, analyses of the 2D model considering the material anisotropy and thermal barrier coating were conducted. The difference in the change in the surface properties and strain distribution according to the presence or absence of cracks was elucidated. The difference in the change in the top surface height distribution of the materials with and without a crack was directly proportional to the crack length. As the value was large with respect to the vertical resolution of 0.2 nm of the digital holographic microscope, the change could be detected by the microscope.

DOI： 10.3390/app10144883

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Evaluation of strength of stainless steel bolt without heat treatment considering Bauschinger effect during manufacturing process 査読

S. Narita, K. Hayakawa, T. Uemori, Y. Kubota

Journal of Materials Processing Technology   278   116481 - 116481   2020年4月

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.jmatprotec.2019.116481

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引張および疲労負荷を受ける純チタン細線の破壊予測に向けた直流電位差および直径分布の変化の分析 査読

坂本 惇司, 高木 佑輔, 上森 武, 多田 直哉

日本機械学会論文集   86 ( 882 )   19 - 00351   2020年2月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本機械学会  

<p>Pure titanium thin wires have been used for medical fields. It is important to investigate the possibility of non-destructive inspection of pure titanium thin wires for the safety utilization of them. In order to investigate a fracture prediction method for a pure titanium thin wire, we performed tensile and fatigue tests and a finite element analysis to analyze the changes of direct current potential difference and diameter distribution of the pure titanium thin wire during tensile and fatigue tests. It was found that a direct current potential difference method may be available for evaluating the tensile and fatigue damages of the pure titanium thin wire. In the tensile and fatigue tests, the normalized direct current potential difference increased almost linearly with an increase in the nominal strain, and a sign of an increase of the normalized direct current potential difference was observed when the fatigue crack propagated. Therefore, the nondestructive inspection could be conducted by setting a tolerance value of the normalized direct current potential difference, or detecting a sign of an increase in the normalized direct current potential difference. In addition, a method of predicting the fracture location from the diameter distribution change of the pure titanium thin wire was studied. The method could be applied to tensile and fatigue fractures.</p>

DOI： 10.1299/transjsme.19-00351

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Microscopic deformation of thin sheet of polycrystalline pure titanium under tension 査読

Naoya Tada, Kentaro Kishimoto, Takeshi Uemori, Junji Sakamoto

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   3   2020年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Copyright © 2020 ASME. Commercial pure titanium has been widely used in aerospace, chemical, and biomedical industries for its lightweight, high corrosion resistance, high strength, high heat resistance and good biocompatible properties. The market of pure titanium thin sheets is expected to increase in medical, dental, civil engineering, and acoustical engineering fields. On the other hand, pure titanium takes hexagonal closed-pack structure with anisotropic elasticity and plasticity. Inhomogeneous microscopic deformation always occurs by mechanical loading from the elastic condition. The inhomogeneity brings about various damages such as localized plastic deformation, microcracking, necking, and so on. Since the inhomogeneity is significant in thin sheets, it is important to investigate its deformation behavior. In this study, a tensile test was carried out using a thin sheet specimen of polycrystalline pure titanium, and the microscopic deformation of grains was measured by the digital holographic microscope. During the test, the height distribution of grains was measured in a fixed area on the front and back surfaces of the specimen at each tensile load step and the results at different load steps were compared. It was found from the measurement results that inhomogeneous deformation began at the small load due to anisotropic elasticity of crystal grains and expanded with the load by their anisotropic plasticity. Grain heights at grain center and those along grain boundaries were related with each other, and the grain heights on the front surface were inversely correlated with those on the back surface.

DOI： 10.1115/PVP2020-21715

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Slip Deformation of Crystal Grains in Semi-Circular Notched Thin Sheet Specimen of Pure Titanium during Tensile Test 査読

Takashi Ishida, Naoya Tada, Takeshi Uemori, Junji Sakamoto

Proceedings of the International Conference on Advanced Technology in Experimental Mechanics 2019 (ATEM ‘19)   2019年10月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Prediction of Fracture Location in Tensile Test of Short-Fiber-Self-Reinforced Polyethylene Composite Plates 査読

Naoya Tada, Ming Jin, Takeshi Uemori, Junji Sakamoto

Conference Papers, ASME 2019 Pressure Vessels and Piping Conference (PVP2019)   3   2019年7月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1115/pvp2019-93546

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Effect of Lubrication and Forging Load on Surface Roughness, Residual Stress, and Deformation of Cold Forging Tools 査読

Karunathilaka, Tada, Uemori, Hanamitsu, Fujii, Omiya, Kawano

Metals   9 ( 7 )   783 - 783   2019年7月

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掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59–61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions.

DOI： 10.3390/met9070783

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純チタン薄板における微視的な不均一変形が表面あれに及ぼす影響に関する結晶塑性有限要素解析 査読

材料   68 ( 6 )   478 - 484   2019年6月

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担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2472/jsms.68.478

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Springback Suppression of AZ31 Magnesium Alloy Sheet in Draw Bending at Elevated Temperature 査読

片平卓志, 上森武, 吉田哲哉, 瀧口三千弘, Komgrit Lawanwong, 吉田総仁

Key Engineering Materials   Vol.794   127 - 132   2019年2月

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Microscopic Elastic and Plastic Inhomogeneous Deformations and Height Changes on the Surface of a Polycrystalline Pure-Titanium Plate Specimen under Cyclic Tension 査読

Naoya Tada, Takeshi Uemori

Applied Sciences   8 ( 10 )   1907 - 1907   2018年10月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

A cyclic tensile test was carried out using a plate specimen of commercial pure titanium on a digital holographic microscope stage. Microscopic deformation of the grains was observed, and their height distribution was measured on the specimen surface. Each grain showed nanoscopic movement up and down, as well as reverse movement corresponding to specimen loading and unloading. We suggest that the different grain-specific changes in height were caused by microscopic inhomogeneities in the material, such as differences in the crystal orientation and geometries of both the surface and subsurface grains. Changes in grain height increased with tensile load, and a strong relationship was found between the height changes that occurred under elastic and plastic conditions. This suggests that microscopic plastic deformation is predictable from microscopic elastic deformation. In order to investigate the plastic deformation of grains in more detail, slip-line angles were measured after the tensile test. We found slip lines with similar angles in neighboring grains, suggesting that the plastic deformation of grains was not independent, but rather was related to that of surrounding grains and influenced by the deformation of subsurface grains.

DOI： 10.3390/app8101907

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Effect of Contact Pressure Applied on Tool Surface during Cold Forging on Fatigue Life of Tool Steel 査読

Nuwan Karunathilaka, Naoya Tada, Takeshi Uemori, Ryota Hanamitsu, Masahiro Kawano

Procedia Manufacturing   15   488 - 495   2018年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Cyclic stress and strain responses of AZ31 magnesium alloy sheet metal at elevated temperatures 査読

Takeshi Uemori, Takashi Katahira, Tetsuo Naka, Naoya Tada, Fusahito Yoshida

Procedia Manufacturing   15   1792 - 1799   2018年

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron 査読

Naoya Tada, Takeshi Uemori

Conference papers, ASME 2018 Pressure Vessels & Piping Conference   PVP2018-85214   2018年

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Elastic and Plastic Microscopic Undulation on the Surface of Polycrystalline Pure Titanium Under Tension 査読

Naoya Tada, Takeshi Uemori, Toshiya Nakata

JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME   139 ( 6 )   1180 - 189   2017年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ASME  

Commercial pure titanium has been widely used in the aerospace, chemical, and biomedical industries because of its light weight, high corrosion resistance, high strength, high heat resistance, and good biocompatibility. Pure titanium takes the form of a hexagonal closed-pack structure with anisotropic elasticity and plasticity, with most of its components being polycrystalline aggregates having different crystal orientations. Small mechanical loading under elastic conditions therefore always induces inhomogeneous microscopic deformation, and the resulting inhomogeneity brings about various defects such as inhomogeneous plastic deformation, microcracking, and necking. It is therefore important to investigate the microscopic inhomogeneous deformation under elastic and plastic conditions. In this study, a plate specimen of commercial pure titanium was subjected to a tensile test on the stage of a digital holographic microscope (DHM), and the microscopic deformation of grains in the specimen under elastic and plastic conditions were observed and measured. During the test, the grains' height distribution was measured in a fixed area on the specimen's surface at each tensile loading step, and the correlation between height distributions at different loads was examined. We found from the measurements that each grain shows a different height change even under elastic conditions with a small load. This inhomogeneous height change was enhanced as the load was increased to plastic conditions. A strong correlation between the height changes under elastic and plastic conditions was also found. This result suggests that the microscopic deformation experienced under plastic conditions is predictable from that observed under elastic conditions.

DOI： 10.1115/1.4038012

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Evaluation of Thin Copper Wire and Lead-Free Solder Joint Strength by Pullout Tests and Wire Surface Observation 査読

Naoya Tada, Takuhiro Tanaka, Takeshi Uemori, Toshiya Nakata

7 ( 8 )   255 - 255   2017年8月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/cryst7080255

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Time-Dependent Fracture of Copper-Cored Lead-Free Solder Ball and Nickel Rod Joints in Air, Distilled Water, and NaCl Solution 査読

Naoya Tada, Takeshi Uemori

IMPACT 2017 Proceedings   2017-   319 - 322   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1109/IMPACT.2017.8255911

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Description of closure of cyclic stress-strain loop and ratcheting based on Y-U model 査読

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

Key Engineering Materials   725   351 - 356   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

This paper proposes a cyclic plasticity model to describe the closure of a cyclic stress-strain hysteresis loop based on the Y-U model. In this model, the backstress moves in a cyclic memory surface following a newly proposed kinematic hardening law. For this model just the same Y-U parameters can be used, and no additional material parameters are needed. By using a supplementary rule, this model is also able to describe ratcheting.

DOI： 10.4028/www.scientific.net/KEM.725.351

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Effect of Hardening Rule for Spring Back Behavior of Forging 査読

Shinobu Narita, Kunio Hayakawa, Yoshihiro Kubota, Takafumi Harada, Takeshi Uemori

Procedia Engineering   207   167 - 172   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Elsevier Ltd  

Geometrical discrepancy between formed part and designed one is one of the major problems for metal forming processes. Spring back behavior is one of the most important factors on the discrepancy, in not only sheet metal forming but also cold forging process. For cold forging process, it is difficult to observe the change in geometry of forgings before and after release of tools/dies, since the workpiece during forging is covered by tools/dies in most cases. Uncertainty remains for the precision on geometrical prediction after spring back of the cold forged part. In the present research, the diameters of extruded shaft at the bottom dead center and after the release of tools/dies were measured to investigate the spring back behavior in the cold forging process. As a result of experiment, the diameter of extruded shaft was increased at the bottom dead center by spring back and decreased after the release by re-extrusion. For these series of change in diameter, FE analyses using isotropic and kinematic hardening models were performed in order to evaluate influence of spring back on the material hardening models in forging process. For kinematic hardening model, Yoshida-Uemori model modified for large strain region was employed. As a result of calculation, both the isotropic and kinematic hardening models showed the similar tendency on the change in diameter with the experimental one.

DOI： 10.1016/j.proeng.2017.10.756

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Theoretical predictions of fracture and springback for high tensile strength steel sheets under stretch bending 査読

207   1594 - 1598   2017年

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.proeng.2017.10.1054

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Asymmetric-shaped bending of adhesively bonded sheet metals 査読

Taro Tokuda, Takeshi Uemori, Tetsuya Yoshida, Michihiro Takiguchi, Fusahito Yoshida

Key Engineering Materials   725   630 - 635   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

In sheet metal industries, press-formed sheet elements are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, the present authors proposed a new technique that first flat sheets are adhesively bonded together and then press-formed into the final products [1]. In previous study, the problem of the die-bending (V-bending and hat-shaped bending) with symmetrical shape has studied. In this study, asymmetric-shaped bending of adhesively bonded sheet metals was investigated by experiments and FEM analysis method. In the case of asymmetric-shaped bending, it was found that the timing of contact from the die corner to the die hypotenuse is early in the press-forming process compared with symmetrical bending (V-bending and hat-shaped bending). For the FEM analysis results, the maximum shear strain in asymmetric-shaped bending was smaller than that in symmetric-shaped bending at the hat-shaped side. Thus, the shape of the die has a large influence on the die-bending of adhesively bonded sheet metals.

DOI： 10.4028/www.scientific.net/KEM.725.630

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Influence of Bauschinger Effect and Anisotropy on Springback of Aluminum Alloy Sheets 査読

Takeshi Uemori, Satoshi Sumikawa, Tetsuo Naka, Ninshu Ma, Fusahito Yoshida

MATERIALS TRANSACTIONS   58 ( 6 )   921 - 926   2017年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

For accurate springback calculations, the development of accurate constitutive equation Yoshida-Uemori model must always be taken into account. However, several springback calculations of other sheet metals by Yoshida-Uemori model have shown wrong agreements with the corresponding experimental data. The reason is why most of them have been calculated from the view point of the accuracy of Bauschinger effect without the strong anisotropy of sheet metal. In the present paper, we have investigated how the initial anisotropy affects the amount of springback for aluminum sheet metals with Bauschinger effect. Specifically, hat bending experiments in R.D. and T.D. were compared with the corresponding calculations. From the above mentioned comparisons, we found that the optimum combination of an anisotropic yield functions and Yoshida-Uemori model is very important for accurate springback analysis.

DOI： 10.2320/matertrans.L-M2017812

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Cracking behavior of thin gold strip deposited on polycarbonate plate under Cyclic and stepwisely-increased tension 査読

Naoya Tada, Yafei Hu, Takeshi Uemori, Toshiya Nakata

108   01004 - 01004   2017年

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1051/matecconf/201710801004

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Tensile Test of Copper-Cored Lead-Free Solder Joints Using Non-Contact Type Testing Device with Permanent Magnets 査読

Naoya Tada, Takeshi Uemori, Toshiya Nakata

SEM Annual 2017 Proceedings   478 - 478   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Springback analysis of aluminum alloy sheet metals by yoshida-uemori model 査読

Takeshi Uemori, Kento Fujii, Toshiya Nakata, Shinobu Narita, Naoya Tada, Tetsuo Naka, Fusahito Yoshida

Key Engineering Materials   725   566 - 571   2017年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

During the last few decades, the enhancement of prediction capability of the sheet metal forming have been increasing dramatically. High accurate yield criteria and wokhardening model (especially, non-linear kinematic hardening model) have a great importance for the prediction of the final shapes of sheet metal. However, the predicted springback accuracy of aluminum alloy sheet metal is not still good due to their complicated plastic deformation behaviors. In the present research, the springback deformation of aluminum alloy sheet metals were investigated by finite element calculation with consideration of initial anisotropy and the Bauschinger effect. In order to examine the effect of the initial and deformation induced anisotropy on the springback deformation, several types of high accurate yield function and hardening rules are utilized in the present research. The calculated springback by Yoshida 6th yield function [1] and Yoshida-Uemori model [2] shows an excellent agreement with the corresponding experimental data, while the other models underestimate the springback.

DOI： 10.4028/www.scientific.net/KEM.725.566

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Evaluation of bonding strength of thin copper wire and lead-free solder by pullout tests 査読

Naoya Tada, Takuhiro Tanaka, Hirotsugu Tabata, Takeshi Uemori, Toshiya Nakata

2016 11th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT)   164 - 167   2016年10月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1109/impact.2016.7799989

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冷間多段鍛造による非調質ボルトの成形および強度解析に及ぼす硬化則の影響 査読

成田 忍, 上森 武, 早川 邦夫, 久保田 義弘

塑性と加工   57 ( 670 )   1070 - 1076   2016年

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本塑性加工学会  

<p>The isotropic hardening model for an elastic-plastic material have often been used for simulation of cold forging processes, by which, however, it is difficult to represent the Bauschinger effect properly. On the other hand, considering the Bauschinger effect is essential for more precise simulation of the forming process as well as the strength of the forged part without heat treatment. One example is a cold-forged bolt of stainless steel. In the present paper, for two multistage cold forming processes of non-heat-treated stainless steel bolts, the simulations of the forming process and the strength were performed by FE analysis using the YU model that is one of the kinematic hardening models being able to express the Bauschinger effect. As a result, the Bauschinger effect during the forming process can be expressed properly. Moreover, by carrying out the analysis on the tensile test of the forged bolt, the difference in strength by between the isotropic and the kinematic hardening models can be estimated clearly. Furthermore, the effect of the forming process on the strength of the forged bolt can also be evaluated appropriately.</p>

DOI： 10.9773/sosei.57.1070

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成形シミュレーションにおけるバウシンガ効果の影響と対策

上森 武

塑性と加工   57 ( 662 )   194 - 198   2016年

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記述言語：日本語   出版者・発行元：一般社団法人 日本塑性加工学会  

DOI： 10.9773/sosei.57.194

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その他リンク： https://jlc.jst.go.jp/DN/JLC/20021776654?from=CiNii

Modeling of anisotropic hardening of sheet metals including description of the Bauschinger effect 査読

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

INTERNATIONAL JOURNAL OF PLASTICITY   75   170 - 188   2015年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The present paper proposes a framework for constitutive modeling of plasticity to describe the evolution of anisotropy and the Bauschinger effect in sheet metals. An anisotropic yield function, which varies continuously with increasing plastic strain, is defined as an interpolation between two yield functions at two discrete levels of plastic strain. Several types of nonlinear functions of the effective plastic strain are proposed for the interpolation. A framework for a combined anisotropic-kinematic hardening model of large-strain cyclic plasticity with small elastic strain is presented, and the details of modeling which is based on the Yoshida-Uemori, model (Yoshida et al., 2002, Yoshida and Uemori, 2002, 2003) are described. The shape of the yield surface and that of the bounding surface are assumed in the model to change simultaneously. The model was validated by comparing the calculated results of stress strain responses with experimental data on r-value and stress-directionality changes in an aluminum sheet (Hu, 2007) and a stainless steel sheet (Stoughton and Yoon, 2009), as well as the variation of the yield surface of an aluminum sheet (Yanaga et al., 2014). Furthermore, anisotropic cyclic behavior was examined by performing experiments of uniaxial tension and cyclic straining in three sheet directions on a 780-MPa advanced high-strength steel sheet. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijplas.2015.02.004

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Microscopic deformation of polycrystalline pure copper wire during tension 査読

Naoya Tada, Yoshitaka Matsukawa, Takeshi Uemori, Toshiya Nakata

229 - 232   2015年10月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1109/impact.2015.7365226

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異種金属接着板の引張り曲げ・曲げ戻しおける接着層のせん断変形挙動 査読

上森 武

日本接着学会誌   51 ( 7 )   347 - 354   2015年7月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本接着学会  

<p>本研究では異種金属接着板の二種類の引張り曲げ・曲げ戻し実験とFEM 解析を行い，接着層に生じるせん断変形挙動について調べた。本研究によって得られた主な結論は，以下の通りである。（1）作成した二つの実験装置を用いて，接着層の曲げ・曲げ戻し時のせん断変形挙動を観察できた。（2）接着層のせん断変形は，ダイ半径と引張り速度の影響を強く受ける。（3）被着体の引張強さが，接着層のせん断変形挙動に大きく関係する。せん断変形を小さく抑えるには，被着体のいずれかに引張強さの小さいものを用いればよい。（4）接着板の曲げ・曲げ戻しにより生じる接着層のせん断ひずみがある値（約1.7）を超えると，接着層ははく離する。（5）先の研究で得られた接着剤の繰返し粘塑性挙動を表現した構成式をFEM に組み込んだ。接着剤の降伏関数として新たな降伏関数を提案しFEM 解析の精度向上を目指したが，期待する成果は得られなかった。</p>

DOI： 10.11618/adhesion.51.347

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Modeling of large-strain cyclic plasticity including description of anisotropy evolution for sheet metals 査読

Fusahito Yoshida, Takeshi Uemori, Hiroshi Hamasaki

Advanced Structured Materials   64   571 - 585   2015年6月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Verlag  

The present paper describes a framework for the constitutive modeling of a large-strain cyclic plasticity to describe the evolution of anisotropy and the Bauschinger effect of sheet metals that is based on the Yoshida-Uemori kinematic hardening model. In the model, the shapes of the yield and the bounding surfaces are assumed to change simultaneously with increasing plastic strain. An anisotropic yield function that varies continuously with the plastic strain is defined by a nonlinear interpolation function of the effective plastic strain using a limited number of yield functions determined at a few discrete points of plastic strain. With this modeling framework, any type of yield function can be used and the convexity of the yield surface is always guaranteed. A set of kinematic parameters can be identified experimentally independent of the anisotropic parameters.

DOI： 10.1007/978-3-319-19440-0_26

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Cyclic plasticity model for accurate simulation of springback of sheet metals 査読

Fusahito Yoshida, Takeshi Uemori

60 Excellent Inventions in Metal Forming   61 - 66   2015年1月

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記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Springer Berlin Heidelberg  

The use of a plasticity model that properly describes material behavior is of vital importance for accurate numerical simulation of sheet metal forming, especially for the prediction of springback. For that purpose a large-strain cyclic plasticity model, so-called Yoshida-Uemori model, was proposed in the kinematic hardening modeling framework. It is able to describe properly material behavior, such as the Bauschinger effect, the workhardening stagnation, strain-range dependent cyclic workhardening, as well as the degradation of unloading stress-strain slope with increasing plastic strain. The model has been implemented into several FE commercial codes, and it is widely used in sheet metal forming industry. By using it, the accurate springback prediction, especially for high strength steel sheets, is made possible.

DOI： 10.1007/978-3-662-46312-3_10

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Implicit stress integration and consistent tangent matrix for Yoshida's 6th order polynomial yield function combined with yoshida-uemori kinematic hardening rule 査読

Hiroshi Hamasaki, Fusahito Yoshida, Takeshi Uemori

Key Engineering Materials   651-653   558 - 563   2015年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

This paper describes fully implicit stress integration scheme for Yoshida's 6th order yield function combined with Yoshida-Uemori kinematic hardening model and its consistent tangent matrix. Cutting plane method was employed for accurate integrations of stress and state variables appeared in Yoshida-Uemori model. In the present scheme, equivalent plastic strain, stress tensor and all the state variables are treated as independent variables in order to handle the 6th order yield function which is not the J2 yield function, and the equilibriums for each variables are solved for the stress integration. Subsequently, exact consistent tangent matrix which is necessary for implicit static finite element simulation was obtained. The proposed scheme was implemented into finite element code LS-DYNA and deep drawing process for aluminum alloy sheet was calculated. The earing appearance after drawing was compared with the experiment.

DOI： 10.4028/www.scientific.net/KEM.651-653.558

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Die-dending of adhesively bonded sheet metals 査読

Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida

Key Engineering Materials   626   103 - 108   2015年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

In this paper, the deformation behavior of adhesive layer in die-Bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-Bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-Bending. (2) The punch radius has a large influence on the die-Bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-Bending at high speed as well as air-Bending. © (2015) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/KEM.626.103

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主せん断ひずみエネルギーによる成形限界の評価 査読

上森 武

軽金属   65 ( 5 )   190 - 195   2015年

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2464/jilm.65.190

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アルミニウム合金板のスプリングバックに及ぼすバウシンガ効果と異方性の影響 査読

上森 武, 澄川 智史, 中 哲夫, 麻 寧緒, 吉田 総仁

軽金属   65 ( 11 )   582 - 587   2015年

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 軽金属学会  

For accurate springback calculations, the development of accurate constitutive equation “Yoshida–Uemori model” must always be taken into account. However, several springback calculations of other sheet metals by Yoshida–Uemori model have shown wrong agreements with the corresponding experimental data. The reason is why most of them have been calculated from the view point of the accuracy of Bauschinger effect without the strong anisotropy of sheet metal. In the present paper, we have investigated how the initial anisotropy affects the amount of springback for aluminum sheet metals with Bauschinger effect. Specifically, hat bending experiments in R.D. and T.D. were compared with the corresponding calculations. From the above mentioned comparisons, we found that the optimum combination of an anisotropic yield functions and Yoshida–Uemori model is very important for accurate springback analysis.

DOI： 10.2464/jilm.65.582

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Finite element analysis of high tensile strength steel sheet by using complex step derivative approximations 査読

Takeshi Uemori, Hiroshi Miyake, Tetsuo Naka, Michihiro Takiguchi, Fusahito Yoshida

Key Engineering Materials   626   187 - 192   2015年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

The framework for the complex step derivative approximations (hereafter CDSA) to calculate the consistent tangent moduli is studied. The present methods is one of the most effective methods to implement any material constitutive equations to the commercial finite element codes and does not suffer from calculation conditions and errors. In order to confirm the efficiency of CDSA, we developed the user subroutine code based on the CDSA using associative J2 flow rules with general nonlinear isotropic hardening rules that is commonly and widely utilized in commercial finite element codes. In this study, the user material subroutine 'Hypela2' of MSC.Marc (ver.2013.0.0) was utilized. The finite element calculation result by the proposal method shows a good agreement with the corresponding result by the MSC.Marc default setting. Also we apply the Yoshida-Uemori back stress model to the CDSA and evaluate this new technique to predict the deformation behavior of high tensile strength steel sheet. © (2015) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/KEM.626.187

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中国四国支部ひずみゲージ講習会開催報告

上森 武

塑性と加工   55 ( 636 )   14 - 14   2014年

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記述言語：日本語   出版者・発行元：The Japan Society for Technology of Plasticity  

DOI： 10.9773/sosei.55.14

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Observations of cyclic deformation behaviors of aluminum sheet and constitutive modeling 査読

Takeshi Uemori, Satoshi Sumikawa, Tetsuo Naka, Fusahito Yoshida

11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014   81   933 - 938   2014年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Aluminum sheet metals have been widely utilized for a light weight construction of automobile. However, these metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical features such as plastic anisotropy of yield stress and small Lankford value. In order to solve the problems, the present author has developed a new constitutive model. The model can describe accurate non-proportional hardening behaviors of aluminum sheet metals. In the present research, some experimental procedures were carried out to reveal the mechanical properties of an aluminum sheet under proportional and non-proportional deformations. The comparisons between experimental data and the corresponding calculated results by the proposed constitutive model confirm the advantages of our model. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.proeng.2014.10.120

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A model of anisotropy evolution of sheet metals 査読

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014   81   1216 - 1221   2014年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Conventional plasticity models assume that shapes of yield surfaces are remain fixed throughout plastic deformation. However, some experiments show that anisotropy is changing with increasing plastic strain. This paper proposes a constitutive model that describes the evolution of anisotropy, both for the stress directionality and r-values, of sheet metals. The evolution of anisotropy is expressed by the change of the yield function as a function of the effective plastic strain. The anisotropy model is validated by comparing the experimental data on AA6022-T43 aluminium sheet (after Stoughton, T. B. and Yoon, J. W., Int J Plasticity 25 (2009) 1777-1817). This model is incorporated into the Yoshida-Uemori kinematic hardening model to describe both the Bauschinger effect and the anisotropy evolution. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.proeng.2014.10.100

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Springback of Aluminum alloy sheet metal and its modeling 査読

Takeshi Uemori, Satoshi Sumikawa, Syohei Tamura, Tetsuo Naka, Fusahito Yoshida

ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES XVI   939   361 - +   2014年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Aluminum alloy sheet metals have been widely utilized for a light weight construction of automobile. However, Aluminum sheet metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical weak features such as lower Young's modulus, strong plastic anisotropy of yield stress, Lankford values, and so on. In order to solve the problems, the present author has developed a new constitutive model called "Modified Yoshida-Uemori model". The present model can describe accurate non-proportional hardening behaviors of Aluminum alloy sheet metals.
In the present research, several experimental procedures were carried out to reveal the mechanical properties of Aluminum alloy sheet metals. From the comparison between experimental data and the corresponding calculated results by our constitutive model, the performance of our model was evaluated. In addition to the above mentioned research, the evaluation of some springback analyses were also carried out. The calculated results show good agreements with the corresponding experimental data.

DOI： 10.4028/www.scientific.net/AMR.939.361

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Deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals

Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida

ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES XVI   939   19 - +   2014年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

In this paper, the deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the cyclic shear deformation of the adhesive layers during the plastic working. Major results obtained are summarized as follows: (1) When the adhesively bonded sheet metals is bent and pulled out at a 90 degrees angle, shear deformation due to bending of the adhesive layer starts shortly before reaching the die corner and unbending starts at the middle of the corner. (2) The die radius has a large influence on the bending behavior. (3) It is possible to suppress shear deformation of the adhesive layer by using a material with small tensile strength as one of the two adherends.

DOI： 10.4028/www.scientific.net/AMR.939.19

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Modeling of Bauschinger Effect During Stress Reversal 査読

Takeshi Uemori, Satoshi Sumikawa, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   84 ( 12 )   1267 - 1272   2013年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-V C H VERLAG GMBH  

It is widely known that the constitutive model of Bauschinger effect is one of key points to conduct the accurate sheet metal stamping. In the present research, the elasto-plasticity behaviors of thin sheet metals were investigated by conducting in-plane cyclic tension-compression tests in the different angle from the pre-strained direction. In order to evaluate the accuracy of constitutive models for describing the above mentioned elasto-plasticity behaviors, including the Bauschinger effect, some numerical experiments were conducted for the corresponding stress paths calculations by using three kinds of constitutive models: the isotropic hardening model (hereafter IH model), Yoshida-Uemori model (hereafter Y-U model), and the modified Yoshida-Uemori kinematic hardening model (hereafter modified Y-U model). From the comparisons, it is found that the author's present constitutive model shows a good agreement with the experimental stress-strain responses.

DOI： 10.1002/srin.201300048

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金属薄板材料の塑性異方性を再現できる使いやすい三次元降伏関数

上森 武

45   119 - 139   2013年6月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ijplas.2013.01.010

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Influence of Anisotropic Yield Functions on Parameters of Yoshida-Uemori Model 査読

Hirotaka Kano, Jiro Hiramoto, Toru Inazumi, Takeshi Uemori, Fusahito Yoshida

CURRENT STATE-OF-THE-ART ON MATERIAL FORMING: NUMERICAL AND EXPERIMENTAL APPROACHES AT DIFFERENT LENGTH-SCALES, PTS 1-3   554-557   2440 - 2452   2013年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

The Yoshida-Uemori model (Y-U model) can be used with any types of yield functions. The calculated stress strain response will be, however, different depending on the function chosen and on the effective plastic strain definition. Thus several modifications to the Y-U model were proposed in the 10th International Conference on Technology of Plasticity [1]. It was ascertained that in the modified Y-U model, the same set of material parameters can be used with von Mises, Hill's 1948, and Hill's 1990 yield function. In this study, Yld2000-2d and Yoshida's 6th-order polynomial type 3D yield function were examined and it was clarified that the same set of Y-U parameters can be used with these yield functions.

DOI： 10.4028/www.scientific.net/KEM.554-557.2440

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Description of Anisotropy and the Bauschinger Effect on Various Types of Steel Sheets 査読

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

11TH INTERNATIONAL CONFERENCE ON NUMERICAL METHODS IN INDUSTRIAL FORMING PROCESSES (NUMIFORM 2013)   1532   158 - 165   2013年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER INST PHYSICS  

To describe the anisotropy of sheets a sixth-order polynomial type 3D yield function is proposed. The yield function is constructed as a sum of several components of the Cazacu-Barlat function (2001) which was derived as an extension of the J2-J3 Drucker yield criterion (1949) to orthotropy using the linear transformation of the stress deviator. In this framework of modeling, the convexity of the yield locus is perfectly guaranteed. The model was validated by comparing the numerical predictions of planar anisotropy of r-values and flow stress directionality, as well as the shape of yield loci, with the corresponding experimental data on several types of steel sheets (high r-valued IF steel and SPCE, and high strength steel sheets of 440-980MPa TS grades). For most of steel sheets, the model of the sum of two J2 components, which involve eight anisotropic coefficients, is sufficient for the description of their anisotropies. For the description of the Bauchinger effect and cyclic workhardening characteristic, Yoshida-Uemori kinematic hardening model (2002a, 2002b, 2003) was employed, which includes a new proposal to describe non-saturation type workhardening.

DOI： 10.1063/1.4806820

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Temperature and Processability of Magnesium Alloy AZ31 on Rectangular Cup Deep Drawing 査読

Yasuhide Nakayama, Tetsuo Naka, Takeshi Uemori, Ichiro Shimizu

ADVANCES IN ENGINEERING PLASTICITY XI   535-536   326 - +   2013年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

The magnesium alloys, that have high specific strength, are often applied to the industrial products. However, the magnesium alloys exhibit low ductility at the room temperature on account of its hexagonal close-packed structure. It is difficult to give large deformation to the magnesium alloys at room temperature. Therefore, the plastic forming of a magnesium alloy sheet needs the process at warm temperature. In the present work, the procedure of thermal-mechanical coupled analyses are employed. The numerical simulations of warm deep drawings have been performed in order to evaluate the dependence of the temperature on the plastic forming of a magnesium alloy AZ31 sheet. The mechanical properties of the magnesium alloy AZ31 shall be described as the functions depending on temperature. The shapes of punches and die holes are rectangle whose aspect ratios are 1.5 or 2.0. The corners of punches and dies are heated locally at 473K. The influence of local heating on the formability have been investigated. The relation between the blank size and the formability has been also estimated. As the results of numerical simulations, it was shown that the formability of deep drawing was improved by local heating to the punch and the die. When the blanks of various sizes were tried, the distributions of the plastic strain rate around the die corner were changed. Therefore, the deviation of the plastic flow and the temperature distribution arose in a sheet. Consequently, it is necessary to optimize the blank sizes according to the shape of die holes in addition to the forming temperature.

DOI： 10.4028/www.scientific.net/KEM.535-536.326

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応力経路変化を伴うアルミニウム板材の応力－ひずみ関係構成方程式

上森 武

2012年12月

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Description of Planer Anisotropy and Cyclic Plasticity Behavior of Aluminum Sheet Based on Crystal Plasticity Theory 査読

Takumi Kobayashi, Kohshiroh Kitayama, Takeshi Uemori, Fusahito Yoshida

MATERIALS AND COMPUTATIONAL MECHANICS, PTS 1-3   117-119   1397 - +   2012年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

In sheet metal forming, the anisotropy and the Bauschinger effect of sheets affect greatly their formability. This paper discusses how the planar anisotropy and cyclic plastic behavior (the Bauschnger effect and cyclic workhardening characteristics) correlate with the crystallographic texture based on the crystal plasticity analysis on A5052-O sheet. The analytical predictions of r-values and the cyclic stress-strain responses are compared with the experimental observations (S. Tamura et al., Materials Trans, 52-5 (2011), pp.868-875).

DOI： 10.4028/www.scientific.net/AMM.117-119.1397

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Direct selective laser sintering of WC-CO cemented carbide by premixing of additives 査読

Hideki Kyogoku, Takeshi Uemori, Akihiko Ikuta, Kenichi Yoshikawa, Hitoshi Ohmori

ASME/ISCIE 2012 International Symposium on Flexible Automation, ISFA 2012   465 - 468   2012年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：American Society of Mechanical Engineers (ASME)  

In this study, the fabrication conditions of WC cemented carbides by direct selective laser melting were investigated. The effects of additives, such as Co, Cu-20%Sn and Cu powders, and laser scanning conditions on laser sintering process were examined to fabricate a sound laser-scanned body of WC cemented carbides. The optimum laser power, scan speed and scan pitch were found out by experiments. It was found that the continuously smooth single-scan track can be obtained at a lower laser power and a higher scan speed by the addition of 30% Cu powder. The smooth surface of the laser-scanned body could be fabricated at a laser power of 9 W, a scan speed of 20 mm/s and a scan pitch of 0.05 mm. Copyright © 2012 by ASME.

DOI： 10.1115/ISFA2012-7182

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平面応力状態におけるIF鋼の弾塑性変形挙動とそのマクロ－メゾモデリング

上森 武

ISIJ International   52 ( 4 )   735 - 742   2012年

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

平面応力状態におけるIF鋼の弾塑性変形挙動とそのマクロ－メゾモデリングについて検討している

DOI： 10.2355/isijinternational.52.735

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OS0303 マグネシウム合金板の面内繰返し実験観察とそのモデル化

上森 武, 片平 卓志, 吉田 総仁, 高津 正秀, 足立 大樹

M&M材料力学カンファレンス   2012 ( 0 )   _OS0303 - 1_-_OS0303-2_   2012年

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記述言語：日本語   出版者・発行元：一般社団法人 日本機械学会  

To investigate the deformation behavior of a magnesium sheet, the finite element calculation was carried out under tension and in-plane cyclic tension-compression test. From the experimental data, the twin deformation was observed during the tensile deformation after uniaxial compression. For the accurate description of the above mentioned twin deformation, we have developed the constitutive equation of twining behavior. From the comparison, it is found that the developed constitutive equations can calculate stress-strain response accurately.

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Porous titanium dental implants fabricated using metal injection molding

Hideki Kyogoku, Makiko Yonehara, Takeshi Uemori, Hideki Nakayama

Proceedings of the International Euro Powder Metallurgy Congress and Exhibition, Euro PM 2012   3   2012年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：European Powder Metallurgy Association (EPMA)  

The porous titanium implants were tried to fabricate by metal injection molding process. Gas-atomized Ti powder and PMMA powders of various mean particle diameters between 20 and 185 μm were used. The pore size was approximately proportional to the diameter of PMMA powder. The relative density and tensile strength of the sintered compact decreased with increasing the mean particle diameter of PMMA powder. The tension and compression tests were performed to examine the mechanical properties of the porous sintered compacts. The tensile strength of the porous sintered compact added 30 vol.%PMMA of diameter of 185 μm was around 300 MPa. It was found that the strength of the porous compact decreases with increasing the amount of addition of PMMA powder. The design of dental implants was investigated by using a FEM analysis. As a result, the porous dental titanium implants were successfully fabricated by metal injection molding process.

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降伏関数の違いが吉田上森モデルの材料パラメータに与える影響

上森 武

Steel Research International   830 - 835   2011年10月

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降伏関数の違いが吉田上森モデルの材料パラメータに与える影響について検討している

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応力経路変化時におけるバウシンガー効果の構成式

上森 武

Steel Research International   819 - 823   2011年10月

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応力経路変化時において生じるバウシンガー効果の実験結果とそのモデリングについて検討している

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Experimental Observation of Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets 査読

Shohei Tamura, Satoshi Sumikawa, Takeshi Uemori, Hiroshi Hamasaki, Fusahito Yoshida

MATERIALS TRANSACTIONS   52 ( 5 )   868 - 875   2011年5月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

Elasto-plasticity behavior of type A5052-O and AA6016-T4 aluminum alloy sheets was examined by performing several experiments of uniaxial tension, biaxial stretching and in-plane cyclic tension-compression. Both sheets exhibit apparent r-value planar anisotropy, especially for AA6016-T4 it is extremely strong. while their flow stress directionality under uniaxial tension is not so significant. Both the sheets show strong cyclic hardening with weak Bauschinger effect. Such material behavior is well described by Yoshida-Uemori kinematic hardening model combined with an appropriate choice of anisotropic yield function. [doi:10.2320/matertrans.L-MZ201101]

DOI： 10.2320/matertrans.L-MZ201101

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Elasto-plasticity Behavior of IF Steel Sheet with Planar Anisotropy and Its Macro-Meso Modeling 査読

Koushirou Kitayama, Takumi Kobayashi, Takeshi Uemori, Fusahito Yoshida

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN   97 ( 4 )   221 - 229   2011年4月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Elasto-plasticity behavior of a IF steel sheet was investigated by performing uniaxial tension tests in three directions (0 degrees, 45 degrees and 90, to the rolling direction of the sheet), in-plane cyclic tension compression test and bi-axial tension test. The sheet has strong planar r-value anisotropy (r(0) = 2.15, r(45) = 2.12 and r(90) = 2.89) but very weak flow stress directionality. Equi-biaxial flow stress is as large as 1.23 times of the uniaxial flow stress These elasto-plasticity deformation characteristics, as well as the Bauschinger effect and cyclic hardening behavior, are well described by a macro plasticity model (Yoshida-Uemori model incorpolating with the 4th-order anisotropic yield function). Further, the simulation of elasto-plasticity stress-strain responses of the sheet were conducted by two types of crystal plasticity models, i.e., Taylor hypothesis based model and CPFEM, using the crystallographic orientation distribution data measured by neutron diffraction method. The models capture most of the above-mentioned deformation characteristics qualitatively, but the predicted anisotropy and the Bauschinger effect are weaker than those of the real material. The CPFEM gives more realistic results than the Taylor model.

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A User-friendly 3D Yield Function for Steel Sheets and Its Application 査読

Fusahito Yoshida, Shohei Tamura, Takeshi Uemori, Hiroshi Hamasaki

8TH INTERNATIONAL CONFERENCE AND WORKSHOP ON NUMERICAL SIMULATION OF 3D SHEET METAL FORMING PROCESSES (NUMISHEET 2011), PTS A AND B   1383   807 - +   2011年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER INST PHYSICS  

A 6th-order polynomial type 3D yield function, which has a high flexibility of describing anisotropic behavior of steel sheets is proposed. A user-friendly scheme of material parameter identification for the model, where only limited experimental data of r-values and yield stresses in three directions (r(0),r(45),r(90) and alp sigma(0),sigma(45),sigma(90)) plus equi-biaxial yield stress (sigma(x) = sigma(y) = sigma(b)) are needed, is presented. The accuracy of this yield function is verified by comparing the numerical predictions with the corresponding experimental data on planar anisotropy of r-values and flow stress directionality, as well as the shape of yield loci, on several types of steel sheets (high r-value IF steel and high strength steel sheets of 440-980MPa TS levels). The advantage of this model is demonstrated by showing a numerical simulation of hole-expansion test.

DOI： 10.1063/1.3623689

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Experimental observation of elasto-plasticity behavior of type 5000 and 6000 aluminum alloy sheets 査読

Shohei Tamura, Satoshi Sumikawa, Takeshi Uemori, Hiroshi Hamasaki, Fusahito Yoshida

Keikinzoku/Journal of Japan Institute of Light Metals   61 ( 6 )   255 - 261   2011年

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Elasto-plasticity behavior of type A5052-O and AA6016-T4 aluminum alloy sheets was examined by performing several experiments of uniaxial tension, biaxial stretching and in-plane cyclic tension-compression. Both sheets exhibit apparent r-value planar anisotropy, especially for AA6016-T4 it is extremely strong, while their flow stress directionality under uniaxial tension is not so significant. Both the sheets show strong cyclic hardening with weak Bauschinger effect. Such material behavior is well described by Yoshida-Uemori kinematic hardening model combined with an appropriate choice of anisotropic yield function.

DOI： 10.2464/jilm.61.255

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面内異方性を持つIF鋼板の弾塑性特性とそのマクロ－メゾモデリング

北山功志郎, 上森 武

97 ( 4 )   221 - 229   2011年

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.97.221

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二軸応力経路が変化した際の高張力鋼板の弾塑性変形挙動

上森 武

51 ( 10 )   1814 - 1818   2010年10月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.P.M2010817

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Prediction of Fracture for High Strength Steel Sheets under Stretch Bending 査読

Tetsuo Naka, Takanori Kurose, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   81 ( 9 )   841 - 844   2010年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-V C H VERLAG GMBH  

Since high strength steel sheets have low ductility, fracture sometimes occurs in their press forming, especially at a die corner under stretch bending. In the present work, the fracture limits of high strength steel sheets under stretch bending were investigated by performing three-points stretch bending experiments with various punch-radii on six types of high strength steel sheets (590-1180MPa). From the experiment, it was found that stronger the sheet lower the fracture limit measured by limit wall stretch, L-max/L-0(L-max: limit wall length of a sheet, L-0: initial wall length). It comes from a fact that the workhardening exponent (n-value) decreases with increasing the strength of the sheet. To predict the fracture limits, a fracture criterion proposed by Yoshida et al., in which limit wall stretch is explicitly given as a function of non dimensional bending radius, t(0)/R (t(0): sheet thickness, R: bending radius) and materials' n-value, was employed. The predicted limit wall stretch, as well as the limit forming height, was in good agreement with the corresponding experimental results.

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Springback Simulation of High Strength Steel Sheets Calculated by Yoshida-Uemori Model 査読

Takeshi Uemori, Satoshi Sumikawa, Shohei Tamura, Hiroyuki Akagi, Tetsuo Naka, Fusahito Yoshida

STEEL RESEARCH INTERNATIONAL   81 ( 9 )   825 - 828   2010年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-V C H VERLAG GMBH  

For the accurate simulation of springback on high strength steel sheets, the use of an appropriate material model is of vital importance. In general, major aspects of material modelling are on the yield function and the hardening law. In the present work, using the framework of Yoshida-Uemori model (F. Yoshida and T. Uemori, Int J Plasticity, 18, 2002, 661-686), which is an advanced kinematic hardening model incorporating with a selected anisotropic yield function, FE simulations of springback in draw bending and S-rail forming (Numisheet'96 model) of 590 and 980MPa levels high strength steel sheets were performed, and the results were compared with the corresponding experimental observations. From the results, it is concluded that the modelling of the Bauschinger effect, including the plastic-strain dependent Young's modulus, is essential for accurate simulation of springback of high strength steel sheets, but the selection of an anisotropic yield function would be of minor effect since most of HSSs have weak anisotropies.

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Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling 査読

Shohei Tamura, Satoshi Sumikawa, Hiroshi Hamasaki, Takeshi Uemori, Fusahito Yoshida

NUMIFORM 2010, VOLS 1 AND 2   1252   630 - +   2010年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER INST PHYSICS  

To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r(0), r(45) and r(90)), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh's biquadratic yield function and Barlat's Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model).

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プレス成形シミュレーションにおける材料モデルの検討

上森 武

2010年

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G0300-5-2 高張力鋼板のスプリングバック解析([G0300-5]材料力学部門一般講演(5):弾塑性解析)

赤木 宏行, 田村 翔平, 澄川 智史, 上森 武, 吉田 総仁

年次大会講演論文集   2010   217 - 218   2010年

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

High tensile strength steel sheets have been widely used in the automobile industries to produce the light weight constructions. However the large springback deformation due to the high flow stress makes it difficult to the final shapes of car parts. In order to solve the problem, we propose the most accurate constitutive equation "Yoshida-Uemori model". In the present report, we evaluated usefulness of the constitutive equation.

DOI： 10.1299/jsmemecjo.2010.1.0_217

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G0300-5-1 均質化手法による金属の繰返し応力-ひずみ関係の数値シミュレーション([G0300-5]材料力学部門一般講演(5):弾塑性解析)

影山 貴大, 上森 武, 吉田 総仁

年次大会講演論文集   2010   215 - 216   2010年

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

With the great development of computer hard technologies, there is a great demand for the accurate finite element analysis which can deal with the morphology of materials. There were so many reports that the complicated plastic deformation behaviors such as "Work hardening", "Bauschinger effect" and "Permanent softening" is related to morphology. We have introduced the Homogenization theory into the commercial finite element code "Marc" in order to research how different stress-strain responses were obtained.

DOI： 10.1299/jsmemecjo.2010.1.0_215

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FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION 査読

Tetsuo Naka, Yasuhide Nakayama, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS: FROM NANOSCALE TO MACROSCALE   638 - 643   2009年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD  

Forming Limit Diagrams (FLDs) of a magnesium alloy (AZ31) sheet at various forming speeds (3 to 300 mm.mm(-1)) at several temperatures of 100-250 degrees C were investigated by performing a punch stretch-forming test. The forming limit strains increased with temperature rise and with decreasing forming speed, where the effect of forming speed was stronger at higher temperatures. To describe such a characteristic of FLD of AZ31, the Marciniak-Kucznski type forming limit analysis was conducted using the Backofen-type constitutive equation (sigma = C epsilon(n) (epsilon) over dot(m)). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane&apos;s ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

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PLASTIC DEFORMATION BEHAVIOR OF HIGH STRENGTH STEEL SHEET UNDER NON-PROPORTIONAL LOADING AND ITS MODELING 査読

Takeshi Uemori, Yuji Mito, Satoshi Sumikawa, Ryutaro Hino, Fusahito Yoshida, Tetsuo Naka

ENGINEERING PLASTICITY AND ITS APPLICATIONS: FROM NANOSCALE TO MACROSCALE   22 - +   2009年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD  

This paper deals with plastic deformations of a high tensile strength steel sheet (HTSS sheet) under biaxial stress condition including strain path. Using a cruciform specimen of a HTSS sheet of 780MPa-TS, experiments under proportional and non-proportional loadings were investigated. Numerical simulations of stress-strain responses for several strain paths after biaxial stretching were conducted using a large-strain cyclic plasticity model (Yoshida-Uemori model). The results of numerical simulation agrees well the corresponding experimental results, which is attributed to the accurate modeling of the backstress evolution of the anisotropic yield function.

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二軸応力経路が変化する場合の高張力鋼板の弾塑性変形挙動

上森 武

塑性と加工   50 ( 576 )   39 - 43   2009年

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記述言語：日本語   出版者・発行元：The Japan Society for Technology of Plasticity  

The elastopasticity behavior of a high-strength steel sheet was investigated by performing biaxial tension experiments. To evaluate the accuracy of constitutive models in describing such elastoplasticity behavior, numerical simulations of stress-strain responses were conducted for the same stress paths as those in the experiments using two types of models: the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida-Uemori model). In this work, special emphasise is placed in the cases of stress-path change. In experiments on radial loadings after equibalanced tension preloading, it was found that flow stresses are considerably lower than uniaxial tension flow stress. The IH model hardly describes this phenomenon, although it is sufficient for stress-strain analysis of proportional loading cases. In contrast, the Yoshida-Uemori model can well predict every stress-strain response in biaxial stress-path changes.

DOI： 10.9773/sosei.50.39

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00324822128?from=CiNii

板材の引張試験， 変形特性と成形性の評価試験

上森 武

2009年

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ショットピーニングによるコールドバットジョイント

上森 武, 兵庫県立大

2009年

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高張力鋼板と異種金属のショットピーニングによるバットジョイント

上森 武, 兵庫県立大

2009年

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非比例変形時における高張力鋼板の塑性変形挙動とそのモデル化

上森 武

22 ( 31-32 )   5394 - 5399   2008年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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温間ストレッチ下におけるAZ31板FLDとその予測

上森 武, 弓削商船高等専門学校

22 ( 31-32 )   6010 - 6015   2008年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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調質圧延における鋼板の不均一塑性変形と降伏点除去過程のFEMシミュレーション(<特集>調質圧延のミクロ変形解析および実機操業技術の最近の進歩)

吉田 総仁, 上森 武, 金田 佑也, 山本 茂雄, 後藤 良孝, 酒井 岳人

鐵と鋼 : 日本鐡鋼協會々誌   94 ( 10 )   384 - 390   2008年10月

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記述言語：日本語   出版者・発行元：社団法人日本鉄鋼協会  

Finite element simulations of temper rolling of a steel sheet were performed using a model of elasto-viscoplasticity that describes the yield-point phenomena such as a high upper yield point, the rate-dependent Luders strain at the yield plateau and the subsequent workhardening. From the simulations of uniaxial tension of temper-rolled sheets, the mechanism of elimination of the yield point by rolling has been clarified. For the purpose of the elimination of the yield point, the roughness of the roll plays an important role. During the temper rolling with rough surface rolls, a number of plastic zones are non-uniformly formed on the surfaces of the sheet, and from these numerous Luders bands will start to propagate simultaneously. Consequently, macroscopic plastic deformation more likely to occur in the temper-rolled sheet under a comparatively low load without showing the yield point.

DOI： 10.2355/tetsutohagane.94.384

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00319515370?from=CiNii

FE Simulation of Non-uniform Plastic Deformation of Steel Sheet and Elimination of Yield Point in Temper Rolling 査読

Fusahito Yoshida, Takeshi Uemori, Yuya Kaneda, Shigeo Yamamoto, Yoshitaka Goto, Gakuto Sakai

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN   94 ( 10 )   A384 - A390   2008年10月

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Finite element simulations of temper rolling of a steel sheet were performed using a model of elasto-viscoplasticity that describes the yield-point phenomena such as a high upper yield point, the rate-dependent Luders strain at the yield plateau and the subsequent workhardening. From the simulations of uniaxial tension of temper-rolled sheets, the mechanism of elimination of the yield point by rolling has been clarified. For the purpose of the elimination of the yield point, the roughness of the roll plays an important role. During the temper rolling with rough surface rolls, a number of plastic zones are non-uniformly formed on the surfaces of the sheet, and from these numerous Luders bands will start to propagate simultaneously. Consequently, macroscopic plastic deformation more likely to occur in the temper-rolled sheet under a comparatively low load without showing the yield point.

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ひずみ速度，温度，板厚の影響がAZ31マグネシウム合金板の降伏曲面に与える影響

上森 武, 弓削商船高等専門学校

201 ( 1-3 )   395 - 400   2008年5月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jmatprotec.2007.11.189

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調質圧延における鋼板の不均一塑性変形と降伏点除去過程のFEMシミュレーション

上森 武

2008年

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DOI： 10.2355/tetsutohagane.94.384

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AZ31マグネシウム合金板のひずみ速度と温度が降伏曲面に与える影響

上森 武, 弓削商船高等専門学校

340-341   119 - +   2007年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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非比例変形を受ける高張力鋼板の塑性変形挙動とそのモデル化

上森 武

340-341   895 - +   2007年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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高精度スプリングバック解析に必要な大ひずみ繰返し塑性構成式

上森 武

340-341   811 - +   2007年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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Effect of strain-rate and temperature on yield locus for 5083 aluminum alloy sheet 査読

T Naka, Y Nakayama, T Uemori, R Hino, F Yoshida

ADVANCES IN ENGINEERING PLASTICITY AND ITS APPLICATIONS, PTS 1 AND 2   274-276   937 - 942   2004年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

To determine yield locus of type, 5083 aluminum-magnesium sheet at elevated temperature, biaxial tensile experiments were performed, using cruciform specimens, at various temperatures (25 - 300 degreesC) at strain rates raging from 10(-5) to 10(-2) s(-1). From the experimental results, the effects of strain rate and temperature on the yield locus are discussed. The size of yield locus drastically decreased with increasing temperature and with decreasing strain rate. Neither von Mises' yield criterion or Hill's can well predict the shape of yield locus of this type of sheet metal. In contrast, the yield criterion of Logan-Hosford or Barlat well simulate the yield locus at elevated temperatures.

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大ひずみ繰返し塑性構成式とスプリングバック解析への応用

上森 武

45 ( 10 )   1687 - 1702   2003年10月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ijmecsci.2003.10.013

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5083アルミニウム合金の降伏曲面に与える温度の影響

上森 武, 弓削商船高等専門学校

140   494 - 499   2003年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0924-0136(03)00780-5

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5083アルミニウム合金の降伏曲面へのひずみ速度と温度が与える影響

上森 武, 弓削商船高等専門学校

140   494 - 499   2003年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0924-0136(03)00780-5

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A model of large-strain cyclic plasticity and its application to springback simulation 査読

F Yoshida, T Uemori

ENGINEERING PLASTICITY FROM MACROSCALE TO NANOSCALE PTS 1 AND 2   233-2   47 - 58   2003年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

This paper presents a framework of constitutive modeling of large-strain cyclic plasticity which describes both the deformation- and texture-induced anisotropies of materials. In this model, the transient Bauschinger effect is described accurately by a new equation of the backstress evolution, and the strain-range and mean-strain dependencies of cyclic strain-hardening are expressed by a model of workhardening stagnation. For the description of texture-induced anisotropy, any of widely accepted yield criteria of orthotropic anisotropy is easily incorporated into this model. This paper demonstrates the advantage of the present model in the springback analysis over other classical models by comparing the FE simulations of draw-bending with the corresponding experimental results.

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大ひずみ繰返し塑性変形挙動を記述する構成式

吉田 総仁, 上森 武

日本機械学會論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A   68 ( 667 )   415 - 421   2002年

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

This paper presents a constitutive model of plasticity that describes the cyclic stress-strain responses at large strain. A new equation of backstress evolution is proposed for an accurate simulation of the transient Bauschinger effect. An original idea of a non-isotropic-hardening surface defined in the stress space is presented for the description of the workhardening stagnation appearing under reverse deformation, as well as the strain-range and mean-strain dependencies of cyclic hardening characteristics. The validity of this model is confirmed by comparing the cyclic stress-strain responses calculated by the model with the experimental observations on two types of steel sheets (an aluminum-killed steel and a dual-phase high strength steel of 590 MPa tensile strength).

DOI： 10.1299/kikaia.68.415

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00155932935?from=CiNii

Importance of Appropriate Modeling of the Bauschinger Effect in Springback Analysis

Journal of the Japan Society for Technology of Plasticity   43 ( 498 )   65 - 69   2002年

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Investigation of Cyclic Elasto-Plastic Behavior of Coppeer Sheet

Key Engineering Materials   2002年

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Elastic-plastic behavior of steel sheets under in-plane cyclic tension-compression at large strain

F Yoshida, T Uemori, K Fujiwara

INTERNATIONAL JOURNAL OF PLASTICITY   18 ( 5-6 )   633 - 659   2002年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Elastic-plastic behavior of two types of steel sheets for press-forming (an aluminum-killed mild steel and a dual-phase high strength steel of 590 MPa ultimate tensile strength) under inplane cyclic tension-compression at large strain (up to 25% strain for mild steel and 13% for high strength steel) have been investigated. From the experiments, it was found that the cyclic hardening is strongly influenced by cyclic strain range and mean strain. Transient softening and workhardening stagnation due to the Bauschinger effect, as well as the decrease in Young's moduli with increasing prestrain, were also observed during stress reversals. Some important points in constitutive modeling for such large-strain cyclic elasto-plasticity are discussed by comparing the stress-strain responses calculated by typical constitutive models of mixed isotropic-kinematic hardening with the corresponding experimental observations. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0749-6419(01)00049-3

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スプリングバック解析におけるバウシンガー効果の適切なモデル化の重要性

塑性と加工   43 ( 498 )   65 - 69   2002年

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高張力鋼板の面内応力反転時の弾塑性挙動とそのモデル化

塑性と加工   43 ( 494 )   59 - 63   2002年

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A model of large-strain cyclic plasticity describing the Bauschinger effect and workhardening stagnation

F Yoshida, T Uemori

INTERNATIONAL JOURNAL OF PLASTICITY   18 ( 5-6 )   661 - 686   2002年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

This paper presents a constitutive model that has a high capability of describing the deformation behavior of large-strain cyclic plasticity and also the stress-strain responses at small-scale re-yielding after large prestrain. A new equation of backstress evolution is proposed for an accurate simulation of the transient Bauschinger effect. Furthermore, an original idea of a non-isotropic-hardening surface defined in the stress space is presented for the description of the workhardening stagnation appearing under reverse deformation, as well as the strain-range and mean-strain dependencies of cyclic hardening characteristics. The validity of this model is confirmed by comparing the cyclic stress-strain responses calculated by the model with the experimental observations on some steel sheets and an aluminum sheet. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0749-6419(01)00050-X

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Investigation of cyclic elasto-plastic behavior of copper sheet

Takeshi Uemori, Fusahito Yoshida

Key Engineering Materials   233-236 ( I )   287 - 292   2002年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Trans Tech Publications Ltd  

The cyclic plasticity behavior of an anisotropic copper sheet metal was investigated by performing in-plane tension-compression experiments. In this copper sheet, the cyclic stress amplitude of a specimen of rolling direction is apparently larger than that of the transverse direction. In order to describe such anisotropic workhardening characteristics in cyclic plasticity, as well as the Bauschinger effect, the new version of Yoshida-Uemori model, which incorporates Gotoh's quadratic yield function of the orthotropic anisotropy, was employed. The cyclic stress-strain responses calculated by this model shows in good agreement with the experimental observations.

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軟鋼板の大ひずみ繰返し塑性変形挙動とその構成モデル

塑性と加工   30 ( 338 )   358 - 364   2001年

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Plasticity Models Describing the Bauschinger Effect and Yield-Point Phenomena

INZYNIERIA MATERIALOWA   974?980   2001年

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FE analysis of springback in hat-bending with consideration of initial anisotropy and the Bauschinger effect

T Uemori, T Okada, F Yoshida

ADVANCES IN ENGINEERING PLASTICITY, PTS 1-2   177-1   497 - 502   2000年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

This paper demonstrates how strongly the analytical prediction of springback is influenced by the description of material's stress-strain responses appearing during stress reversal. For the finite element analysis of hat-bending and the subsequent springback, three different types of constitutive models, i.e., (a) isotropic hardening (IH) model, (b) linearly kinematic hardening (LKH) model, and (c) combined hardening (IH+LKH+non-linearly kinematic hardening [NLKH]) model, were employed. When using the combined hardening model, the calculated sheet geometries showed the excellent agreement with the experimental results, while the predictions by both the IH and LKH models underestimate the springback.

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Simulation of springback in V-bending process by elasto-plastic finite element method with consideration of Bauschinger effect

T Uemori, T Okada, F Yoshida

METALS AND MATERIALS-KOREA   4 ( 3 )   311 - 314   1998年

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：KOREAN INST METALS MATERIALS  

This paper presents the prediction of springback in sheet metal forming in terms of the description of the Bauschinger effect. It addresses three different types of constitutive models: an iso-tropic hardening model (IH model), a linearly kinematic hardening model (LK model), and a model of combined linearly-nonlinearly kinematic and isotropic hardening (L-NK+IH model). The springback predicted by the L-NK+IH model is found to be more pronounced than that by the III and the LK model. It is caused by the stress-strain response characterized by the gradual transition from fully elastic to plastic behavior during stress-reversal, which is essential to the L-NK+IH model.

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Prediction of active slip system for commercially pure titanium sheet by crystal plasticity finite element analysis

Takeshi UEMORI, Naoya TADA, Junji SAKAMOTO, Masatoshi DOI

Extended abstract of The Advanced Technology in Experimental Mechanics and International DIC Society Joint Conference 2023 (ATEM-iDICs '23)   19-G05   1900年

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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