Faculty Profiles - UEMORI Takeshi

Papers - UEMORI Takeshi

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

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

STEEL RESEARCH INTERNATIONAL 81 ( 9 ) 825 - 828 2010.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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.

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

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

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

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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).

Constitutive modeling for Sheet Metal Forming Simulation

2010

G0300-5-1 Numerical simulation of cyclic stress-strain responses for sheet metals by homogenaization method

KAGEYAMA Takahiro, UEMORI Takeshi, YOSHIDA Fusahito

The proceedings of the JSME annual meeting 2010 215 - 216 2010

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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

G0300-5-2 Springback analysis of high tensile strength steel sheet

AKAGI Hiroyuki, TAMURA Syohei, SUMIKAWA Satoshi, UEMORI Takeshi, YOSHIDA Fusahiro

The proceedings of the JSME annual meeting 2010 217 - 218 2010

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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

FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION Reviewed

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

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

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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's ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

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

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

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

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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.

Elasto-plastic defomation behavior of high tensile strength steel sheet under the strain path changes

UEMORI Takeshi, KURAMITSU Tohru, MITO Yuji, HINO Ryutaro, NAKA Testuo, YOSHIDA Fusahito

Journal of the JSTP 50 ( 576 ) 39 - 43 2009

Language：Japanese Publisher：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

Other Link： https://jlc.jst.go.jp/DN/JALC/00324822128?from=CiNii

Material testing (tension test and evaluation for deformation behavior and formability)

2009

Cold Butt Joining Steel Sheet by Shot Peening

2009

Butt Joining of Hight Strength Steel Sheet and Dissimilar Metal Sheet by Shot Peening

2009

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

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

INTERNATIONAL JOURNAL OF MODERN PHYSICS B 22 ( 31-32 ) 5394 - 5399 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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.

FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION

Tetsuo Naka, Yasuhide Nakayama, Takeshi Uemori, Ryutaro Hino, Fusahito Yoshida, Masahide Kohzu, Kenji Higashi

INTERNATIONAL JOURNAL OF MODERN PHYSICS B 22 ( 31-32 ) 6010 - 6015 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (c = C epsilon(n)epsilon(m)). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane's ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

FE Simulation of Non-uniform Plastic Deformation of Steel Sheet and Elimination of Yield Point in Temper Rolling(<Special Issue>Progress of Analysis on Micro-plasticity and Practical Technology in Temper Rolling)

YOSHIDA Fusahito, UEMORI Takeshi, KANEDA Yuya, YAMAMOTO Shigeo, GOTO Yoshitaka, SAKAI Gakuto

Tetsu- to- Hagane 94 ( 10 ) 384 - 390 2008.10

Language：Japanese Publisher：The Iron and Steel Institute of Japan (ISIJ)

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

Other Link： 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 Reviewed

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 2008.10

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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.

Effects of strain rate, temperature and sheet thickness on yield locus of AZ31 magnesium alloy sheet

Tetsuo Naka, Takeshi Uemori, Ryutaro Hino, Masahide Kohzu, Kenji Higashi, Fusahito Yoshida

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 201 ( 1-3 ) 395 - 400 2008.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Magnesium alloys usually exhibit low ductility at the room temperature due to its hexagonal close-packed structure, but it will be improved at elevated temperature. Therefore, warm press-forming of magnesium alloy sheets is quite attractive. In order to determine the optimum condition of press-forming for magnesium alloy sheets, in the present work, the effects of strain rate, temperature and sheet thickness on the yield locus were experimentally investigated. The yield loci of magnesium alloy (AZ31) sheets with different sheet thickness (0.5 and 0.8 mm) were obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 100, 150, 200, 250 and 300 degrees C at strain rates of 10(-2), 10(-3) and 10(-4) s(-1). Based on the experimental results, the effects of strain rate, temperature and sheet thickness on the yield locus were discussed. The size of yield locus drastically decreases with increasing temperature and decreases with decreasing strain rate. in contrast with the temperature and strain-rate dependence of the yield locus, sheet thickness has no influence on the yield locus. The shape of the yield locus of magnesium sheet is far from the predictions calculated by the yield functions of von Mises, Hill and Cazacu. Instead of these, the yield functions of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial tension stress-strain responses at high temperature. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.11.189

Finite element simulation

2008

Effects of strain rate and temperature on yield locus for AZ31 magnesium alloy sheet

Tetsuo Naka, Masanori Hayakashi, Yasu Hide Nakayama, Takeshi Uemori, Masahide Kohzu, Kenji Higashi, Fusahito Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2 340-341 119 - + 2007

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

The yield locus of type AZ31 magnesium alloy sheet was obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 100, 150, 200, 250 and 300 degrees C at strain rates of 10(-2), 10(-3) and 10(-4) s(-1). Based on the experimental results, the effects of strain-rate and temperature on the yield locus was discussed. The size of yield locus drastically decreased with increasing temperature and decreased with decreasing strain-rate. Neither von Mises's criterion or Hill's can well predict the shape of the yield locus of this sheet metal. Instead of these quadratic yield functions, the yield criterion of Logan-Hosford or Barlat is a better choice for the accurate description of biaxial stress-strain responses at high temperature.

Plastic deformation behavior of high strength steel sheet under non-proportional loading and its modeling

T. Uemori, T. Kuramitsu, R. Hino, T. Naka, F. Yoshida

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2 340-341 895 - + 2007

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

This paper deals with experimental observations and modeling of plastic deformations of a high strength steel sheet (HSS sheet) under biaxial stress conditions. Using a cruciform specimen of a HSS sheet of 980MPa-TS, experiments of proportional and non-proportional loadings were performed. Numerical simulations for the biaxial stress-strain responses were conducted using a constitutive model of large-strain cyclic plasticity (Yoshida-Uemori model), and the results were compared to the experimental data. The results of numerical simulation show a good agreement with the experimental results, which is attributed to accurate modeling of the backstress evolution of the anisotropic yield surface.

Modeling of large-strain cyclic plasticity for accurate springback simulation

F. Yoshida, T. Uemori, S. Abe

ENGINEERING PLASTICITY AND ITS APPLICATIONS FROM NANOSCALE TO MACROSCALE, PTS 1 AND 2 340-341 811 - + 2007

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

This paper describes a model of large-strain cyclic plasticity and its verification by some experiments of cyclic plasticity and biaxial stretching. The performance of this model in springback simulation is discussed by comparing the calculated results for S-rail forming with the experimental data on high strength steel sheet (HSS) of 980MPa-TS. The results of numerical simulations of the springback agree well with the corresponding experimental data, including the torsion-type springback appearing in S-rail forming.

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