Problems in Damage Analysis Under Nonproportional Cycling

This paper uses examples to illustrate problems in damage analysis under nonproportional cycling. Nonproportional histories examined include multiaxial loading with either fixed or rotating principal directions. Currently popular concepts advanced for use in damage analysis of nonproportional cycling are reviewed and examined in terms of their potential ability to assess damage for example histories. It is shown that while such damage measures may be valid for mildly nonproportional histories, their successful application to general nonproportional cycling is unlikely. The paper closes with a commentary on the issues considered.