Application of cyclic plasticity to fatigue modeling

Fatigue modeling is a fundamental step in the design against fatigue failure. The formulation of mathematical relations to correlate material deformation such as stress, strain, or energy to fatigue life requires an understanding of the cyclic behavior of material including complex phenomena such as nonproportional hardening. Multiaxial fatigue damage models are developed based on the basic principle that multiaxial deformation can be mapped onto uniaxial deformation. Depending on the assumed damage variables in a given parameter, low cycle fatigue models can be strain- or energy-based. Essentially, fatigue damage is associated with the formation of cracks that generally grow along certain orientations. Therefore, the evaluation of a fatigue damage parameter on selected planes is known as the critical plane concept. This chapter covers different aspects of strain- and energy-based fatigue damage modeling methods. Important topics such as fatigue crack behavior, cyclic nonproportional hardening, and damage accumulation are discussed. The chapter ends by explaining the link between material constitutive properties, fatigue damage model, and cyclic plasticity model to predict the fatigue failure of structures.