Analytical and experimental evaluations of the influence of fracture surface roughness, its sliding actions and the associated plasticity on fatigue crack propagation

An investigation of fatigue crack propagation in rectangular AM60B magnesium alloy plates containing an inclined through crack is presented in this paper. The behavior of fatigue crack growth in the alloy is influenced by the fracture surface roughness. Therefore, in the present investigation, a new model is developed for estimating the magnitude of the frictional stress intensity factor, kf, arising from the mismatch of fracture surface roughness during in-plane shear. Based on the concept of kf, the rate of fatigue crack propagation, db/dN, is postulated to be a function of the effective stress intensity factor range, Δkeff. Subsequently, the proposed model is applied to predict crack growth due to fatigue loads. Experiments for verifying the theoretical predictions were also conducted. The results obtained are compared with those predicted using other employed mixed mode fracture criteria and the experimental data.