Papers by Author: Takeshi Uemori

Abstract: 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.

Abstract: 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.

Abstract: 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 P o PC at strain rates of 10P -2 P, 10P -3 P and 10P -4 PsP -1 P. 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.