# YIELD STRESS BASED ON NATURAL STRAIN THEORY UNDER CYCLIC SHEAR LOAD AFTER LARGE SIMPLE SHEAR

### YASUYUKI KATO

This paper describes the variation of yield stress under cyclic loads after applying large pre-deformation. In this research, the Natural Strain is used as a strain representation for describing an elastoplastic behavior under large deformation. Using test pieces which is already given a pre-deformation of large simple shear, the yield stress under cyclic shear loads in the forward direction and the reverse direction is examined. As for the method for estimating yield stress in each cycle, the slope of a tangent in the principal deviatoric stress and the principal deviatoric strain curve is adopted. The experiments are conducted with the different sizes of pre-deformation and strain amplitude in order to reveal the effect of pre-deformation on the yield phenomenon. Then, these experimental results are compared with the results of yield stress in the previous study, which is obtained under cyclic load for tension and compression after applying the large uniaxial tension.

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