Mixed-mode propagation of fatigue crack in CTS specimen

In this paper, the mixed-mode fatigue tests are carried out using the CTS specimen (Compact-Tension-Shear) and the mixed-mode loading device developed by Richard [1]. Three loading angles and two materials are selected in the experiments. The effect of loading angle on the crack propagation is analyzed numerically and experimentally. According to the experimental results, the fatigue crack growth rate is found to be related to the loading angle. For the same initial equivalent stress intensity factor (combination of the stress intensity factors in mode I and mode II), the crack grows the slowest under pure mode I loading. The photos of crack bifurcation and the results of the crack growth rate in different specimens under different mixed-mode loadings are presented. Furthermore, a numerical model for the fatigue crack propagation is proposed on the basis of the experimental results to evaluate the influences of loading mode on the crack growth rate. The validation of the model is shown for the steel specimens under mixed mode loading. The numerical evaluations are in good agreement with the experimental results.