抄録
The Natural Strain is obtained by integrating an infinitesimal strain increment on identical line element. Since the rigid body rotation can be removed from the rotating angle of a line element and the additive law of strain on an identical line element can be satisfied, the Natural Strain theory is effective strain expression for representing a large plastic deformation. In the previous report, using the Natural Strain theory, the shape of yield surface and the distribution of modulus of strain hardening h around the yield surface have been examined by conducting the proportional loading tests for tension and torsion after giving the pre-deformation of uni-axial tension or simple shear. In this paper, the shape of the yield surface, which is obtained after giving the pre-deformation of proportional loading for tension and shear, is estimated by examining the modulus of strain hardening h in various directions in the stress space.
