Shear Strain Localization in Plastic Deformations

Shear instabilities in the form of shear bands are often observed during high speed, plastic deformations of metals. According to one theory, their formation is attributed to eeective strain-softening response, which results, at high strain rates, as the net outcome of the innuence of thermal softening on the, normally, strain-hardening response of metals. In order to test the core instability mechanism set forth by such theories, we consider one-dimensional shear deformations of a material exhibiting strain softening and strain-rate sensitivity. The deformation is caused by either prescribed tractions or prescribed velocities. As it turns out, for moderate amounts of strain softening, strain-rate sensitivity exerts a dissipative eeect and stabilizes the motion. However, once a threshold is exceeded, the response becomes unstable and shear strain localization can occur.