SHAPE OF YIELD SURFACE ESTIMATED BY USING NATURAL STRAIN UNDER PRE-DEFORMATION OF SHEAR AFTER UNIAXIAL TENSION

Abstract

In the present paper, the anisotropy of yield surface generated under large deformation is investigated on the basis of the Natural Strain theory, which can be treated systematically from the infinitesimal deformation to the large deformation. After applying the pre-deformation of uniaxial tension, simple shear and combined load of them to the test pieces, proportional loading tests are carried out again with changing the ratio of tension and torsion. Then, the shape of yield surface is investigated by estimating the yield stress in an arbitrary direction in the stress space. As the method for determining the yield stress, the slope of the tangent at yielding in the deviatoric stress-deviatoric strain curve is used. In order to reveal the influence of deformation history on the development of anisotropy in yield surface, the pre-deformation that the deformation history is different from previous study, namely, the pre-deformation of shear after uniaxial tension, is examined in this study. Then, the relation between the development of anisotropy in the yield surface and the deformation history of pre-deformation is revealed by comparing with the results of previous study.