A numerical study of transient fatigue crack growth by use of an irreversible cohesive zone model

Abstract

Transient fatigue crack growth is studied for a material system in which the crack tip is shielded due to crack bridging. The process of material separation during fatigue crack growth is described by the use of an irreversible cohesive zone model. In contrast to past developments of cohesive zone models, the traction–separation behavior does not follow a predefined path, but is dependent on the evolution of the damage dependent cohesive zone properties. The model definition is given and the basic uniaxial response of the model documented. The cohesive zone model is subsequently applied in a numerical study of transient fatigue crack growth. Single overload cases are computed to demonstrate the effects of variations in the cohesive zone properties. Block loading sequences with variations in the amplitude and the load ratio are computed. Model predictions qualitatively compare well to experimentally observed effects of fatigue crack growth transients in materials with crack bridging zones.