A damage postulate for nonproportional cyclic plasticity

This paper examines damage states and analysis for the multiaxial mechanical component of a general thermal-mechanical cyclic loading. Specifically, multiaxial histories developed under nonproportional cyclic plasticity synthesized through appropriate constitutive theories are used as a vehicle to discuss nonproportional damage processes and analysis. Nonproportional damage processes considered include both fixed and rotating principal planes. These are discussed in the context of an extension of a recent damage postulate for analysis of nonproportional action with fixed principal directions. It is shown that current data bases developed for use in damage analysis are, in general, inappropriate for applications to nonproportional cycling. The influence of transient inelastic response observed in studies of proportional cyclic plasticity on the damage state is also discussed. (orig.)