Shear Band Analysis in the Biaxial Test

Abstract

Simulation of a biaxial test by finite-element calculations may lead to unexpected localized deformations even for an elastic-perfect plastic Mohr–Coulomb model. The effects of localization lead to difficulties in computations. This paper describes a simple model for the strength development after occurrence of localization. The localization model describes the postfailure behavior assuming elastoplastic behavior inside the shear band and elastic behavior of the material outside the shear band. The resulting two nonlinear equilibrium equations are analyzed with a rigorous nonlinear scheme. The nonlinear equations show snap-through and snap-back behavior. Snap-back occurs due to energy release of unloading of the material outside the shear band. The simulations show that localization in shear bands is possible for orientations between the Roscoe and Mohr–Coulomb direction. Shear bands with orientations close to the Roscoe direction show a more gradual decrease of strength in comparison to bands with orientations close to the Coulomb direction. The flexibility of the shear band is shown to be important for postbifurcation behavior.