ON SHEAR BAND FORMATION:

Abst raet-A phenomenological constitutive relation, for capturing the shear band formation in a rate-independent elastic-plastic material, is established. The model takes into account both the J2-isotropic flow and a threshold shear stress-based flow. The elastic-plastic constitutive t n-sor is expressed explicitly in terms of elastic constants, the deviatoric stress tensor, the direc-tion of the principal shear velocity-strain, and other material constants. This model particularly facilitates the resolution of the formation of the shear band even under material hardening con-ditions and does not demand an a priori knowledge of the orientation of the shear band. This is incorporated in an FEM, and the plane strain tensile test of ANAND and SPITZIG [1980] is numerically simulated. The computed results compare favorably with the experimental data. The shear band emerges more naturally as a solution to the boundary value problem, unlike the situations in solutions based on classical bifurcation methods. Nevertheless, the usefulness of the local instability condition (ORTIZ et aL [1987]) is also demonstrated. 1