Modeling of the variability of fatigue crack growth using cohesive zone elements

Research highlights

► Cohesive zone elements allow to model fatigue crack initiation and growth. ► An algorithm reducing extensively the simulation time with little loss of accuracy was developed. ► The variability inherent in the fatigue life was assessed using a random field model. ► Both crack initiation and propagation are described by the same model.

Abstract

By its nature, metal fatigue has random characteristics, leading to extensive scatter in the results. Both initiation and propagation of a fatigue crack can be seen as random processes. This manuscript develops a numerical analysis using cohesive zone elements allowing the use of one single model in the finite element simulation of the complete fatigue life. The present formulation includes a damage evolution mechanism that reflects gradual degradation of the cohesive strength under cyclic loading. The uncertainties inherent to the fatigue process are assumed to be caused by the variability of the material properties, which are modeled using random fields. An extrapolation scheme is proposed to reduce the computational time. First, the accuracy of the proposed formulation is assessed considering a deterministic crack growth problem. Second, the effect of randomness in the material properties on the total fatigue life of a structure is then analyzed.