Simulation of fatigue crack growth with a cyclic cohesive zone model

Fatigue crack growth is simulated for an elastic solid with a cyclic cohesive zone model (CZM). Material degradation and thus separation follows from the current damage state, which represents the amount of maximum transferable traction across the cohesive zone. The traction-separation relation proposed in the cyclic CZM includes non-linear paths for both un- and reloading. This allows a smooth transition from reversible to damaged state. The exponential traction-separation envelope is controlled by two shape parameters. Moreover, a lower bound for damage evolution is introduced by a local damage dependent endurance limit, which enters the damage evolution equation. The cyclic CZM is applied to mode I fatigue crack growth under -controlled external loading conditions. The influences of the model parameters with respect to static failure load , threshold load and Paris parameters are investigated. The study reveals that the proposed endurance limit formulation is well suited to control the ratio independent of and . An identification procedure is suggested to identify the cohesive parameters with the help of Wohler diagrams and fatigue crack growth rate curves.