The energy criterion for deformation banding in ductile single crystals

The phenomenon of spontaneous formation of deformation bands in metal single crystals deformed plastically by crystallographic multislip is investigated theoretically by using the energy criterion of instability of a uniform deformation path. The second-order energy criterion for incipient deformation banding is derived in a time-continuous setting for a rate-independent elastic–plastic crystal. The need for selective symmetrization of the local interaction matrix for active slip-systems is demonstrated. A computational approach to deformation banding is developed by using non-convex constrained minimization of the incremental work with respect to increments in crystallographic shears and kinematical degrees of freedom. Calculated examples of deformation banding patterns in fcc single crystals are compared with experimental observations.