Plastic Instability Criteria for Necking of Bars and Ballooning of Tubes

摘要

Plastic instability criteria for rate-sensitive materials have been derived in two cases. The first concerns necking in bars under uniaxial tension, and the second ballooning in thin-wall tubes under internal pressure and axial loading. These derivations, primarily based on geometrical considerations, differ in approach from most previous investigations. The results obtained enable explanation of certain interrelationships of uniform elongation, localized deformation, superplasticity, the state of stress and strain, and the material's hardening capability and strain-rate sensitivity. (ERA citation 03:008440)