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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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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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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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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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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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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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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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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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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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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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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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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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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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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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.proeng.2017.10.1054

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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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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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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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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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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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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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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.9773/sosei.57.1070

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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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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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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11618/adhesion.51.347

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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.

CiNii Article

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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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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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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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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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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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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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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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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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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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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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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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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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DOI： 10.9773/sosei.50.39

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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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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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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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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DOI： 10.2355/tetsutohagane.94.384

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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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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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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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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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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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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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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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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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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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DOI： 10.1299/kikaia.68.415

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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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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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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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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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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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開催年月日： 2020年

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開催年月日： 2020年

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開催年月日： 2019年

記述言語：日本語  

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開催年月日： 2019年

記述言語：日本語  

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開催年月日： 2019年

記述言語：日本語  

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開催年月日： 2019年

記述言語：日本語  

<p>Various mechanical components are subjected to random multiaxial vibration. For their safe and effective operation, it is essential to precisely evaluate the fatigue strength of the materials under multiaxial random vibration. However, the mechanisms and evaluation methods remain unclear. In this study, we performed the multiaxial random vibration experiments using aluminum alloy A5056 specimens in order to discuss a method for evaluating the vibration fatigue strength of materials. The multiaxial random vibration experiments were conducted at an acceleration input of 70 G_rms within a frequency band of 10–5000 Hz under a nitrogen gas environment at a room temperature. During the multiaxial random vibration experiments the strains of the specimen were measured using 3-axis and 1-axis strain gauges and the maximum principal strains and their directions of a fracture part were estimated. Based on the results, the method for evaluating the vibration fatigue strength of materials was discussed.</p>

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開催年月日： 2017年6月5日

記述言語：日本語  

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開催年月日： 2017年6月5日

記述言語：日本語  

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開催年月日： 2016年6月3日

記述言語：日本語  

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開催年月日： 2016年6月3日

記述言語：日本語  

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開催年月日： 2016年6月3日

記述言語：日本語  

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開催年月日： 2015年6月5日

記述言語：日本語  

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開催年月日： 2015年6月5日

記述言語：日本語  

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開催年月日： 2015年2月27日

記述言語：日本語  

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開催年月日： 2014年9月22日

記述言語：日本語  

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開催年月日： 2014年9月22日

記述言語：日本語  

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開催年月日： 2013年11月1日

記述言語：日本語  

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開催年月日： 2013年9月8日

記述言語：日本語  

In recent years, high-tensile steel sheets (hereafter HSS) have been widely used in car products in order to satisfy high collision safety and low fuel consumption. Owing to the high yield stress, it is still difficult to predict the final shapes of HSS by using commercial finite element codes. The improvement of prediction for wrinkling, fractures and spring back have been strongly demanded. In order to satisfy the demand, a new high order yield function (we call Yoshida 2012 yield function) was introduced into the ommercial finite element code Marc 2013 in the present research. The evaluation of this yield function was conducted. From the comparisons of experiment and its calculations, it is found that the accuracy of this yield function is quite well and spring back calculation by using this function also moderate.

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開催年月日： 2013年6月10日

記述言語：日本語  

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開催年月日： 2013年5月20日

記述言語：日本語  

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開催年月日： 2013年2月25日

記述言語：日本語  

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開催年月日： 2012年2月28日

記述言語：日本語  

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開催年月日： 2012年2月28日

記述言語：日本語  

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開催年月日： 2012年2月28日

記述言語：日本語  

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開催年月日： 2011年9月11日

記述言語：日本語  

It is one of the difficult problems to predict the final shape of automobile parts. In order to solve the problems, the great demands to the finite element an analysis have been needed. Especially, it demands for an accurate analysis for the multi-stamping procedures have been increasing. The present research proposes the accurate constitutive models which can deal with the stress-strain responses (the Buschinger effect and the cross effect) du ring stress path changes. The calculated results are compared with the corresponding experimental results. From the comparisons, we can conclude the developed constitutive model is effective to increase the accuracy of sheet stamping finite element calculations.

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開催年月日： 2011年2月23日

記述言語：日本語  

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開催年月日： 2011年2月23日

記述言語：日本語  

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開催年月日： 2011年2月23日

記述言語：日本語  

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開催年月日： 2011年2月23日

記述言語：日本語  

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開催年月日： 2011年2月23日

記述言語：日本語  

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記述言語：日本語   会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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