CONSTITUTIVE RELATIONS FOR SINGLE-CRYSTAL BASED ON 2 SURFACE DESCRIPTION

A two surface model is used to describe single crystal slip. The evolu tion of the yield surface and outer yield surface are proposed to be d irectly related to the development of dislocation structures. The anis otropy of inner yield surface is attributed to both the long range and short range dislocation interactions, whereas anisotropy of the outer yield surface is assumed to depend solely on the short range interact ions. The outer yield surface is not isotropic as assumed in most two surface models of other researchers. This surface is able to evolve ev en when the stress state is within the outer yield surface.