研究者詳細 - 上森　武

論文 - 上森　武

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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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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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