Abstract
The continuum mechanics framevork for analyzing necking and shear band instabilities is discussed. The predicted onset of instability depends sensitively on the material's constitutive characterization, not only through properties, such as strain hardening and strain rate sensitivity, that can be measured in proportional loading tests, but also through the material's response to a change in loading path. A specific problem is discussed that illustrates the influence of the curvature of flow potential surfaces even when a softening mechanism plays a major role in precipitating localization