Statistical distribution of mechanical properties to initiate adiabatic shear banding in thick walled collapsing cylinders

Adiabatic shear bands (ASB) are observed in the vast majority of ductile metals subjected to extreme loadings. They are characterized by narrow zones (few micro-meters) where a localization of shear deformation occurs, and are often associated with peaks of temperature as in highly dynamic cases, heat conduction does not smooth the temperature field.

Recent works by Rittel and al., 2006 identified dynamic stored energy of the deformation process as the mechanism responsible for the formation of ASB. Constitutive models have therefore been proposed to include this positive feedback mechanism to trigger the formation of ASB. An energy-based damage parameter (see Dolinski and al., 2010) is used to capture the flow stress decrease.

However, an initial perturbation is required to break the symmetry and initiate ASB. While geometric perturbations in the mesh are often used, in this presentation, an approach based on a statistical distribution of mechanical properties as the initial perturbation is proposed. Properties are distributed on a mesh-independent pattern to ensure numerical repetability. Influence of cell sizes and amplitude of perturbation on shear band patterns is discussed on collapsing cylinders experiments by Lovinger and al., 2011.