Plastic Bifurcation in the Triaxial Confining Pressure Test

Abstract

Bifurcations of a circular cylinder are studied, within the context of the triaxial confining pressure test, for pressure sensitive solids. Material response is modeled by large strain versions of flow and deformation theories of plasticity in conjunction with the Drucker-Prager solid. An axially symmetric deformation pattern is assumed prior to bifurcation and only diffuse modes within the elliptic regime are considered. The governing equations are solved analytically in terms of Bessel functions and a search procedure is employed to trace bifurcation loads. Deformation theory predicts critical stresses which are consistently below flow theory results, and provides practical upper bounds on experimentally observed values of peak stresses. [S0021-8936(00)01403-3]