THE EFFECT OF STRESS-INDUCED ANISOTROPY ON SHEAR BAND FORMATION

This paper describes the effect of non-coaxiality arising from materia l anisotropy on bifurcation phenomena such as shear band formation. Th e elasto-plastic model originally proposed by Sekiguchi and Ohta [7] i s one of the typical models which include anisotropy and it is used to examine the effect of anisotropy on shear band formation. First, we s hall extend this elasto-plastic model for infinitesimal strain to a mo del for finite strain and discuss the mathematical structure of this m odel. The stress induced anisotropy is found to bring about a vertex-l ike effect, such as the non-coaxiality between the Cauchy stress tenso r and a plastic stretching tensor, into the constitutive relation. The n, we shall examine the effect of this non-coaxiality on bifurcation c onditions in relation to the material rigidity which changes with the angle of simple shear. Finally, it will be concluded that this non-coa xiality arising from the anisotropy does not contribute much to trigge ring instability by localization of the deformations which result in s hear band formation, while on the other hand, the non-coaxiality due t o the yield vertex effect is rather inclined towards instability by lo calization of the deformations.