The mixed-mode propagation of fatigue crack in CTS specimen

In this paper, the mixed-mode fatigue tests are carried out with the CTSspecimen (Compact-Tension-Shear) and the mixed-mode loading device developedby Richard 1. Three loading angles and two materials are selected in theexperiments. The effect of loading angle on the crack propagation isanalyzed numerically and experimentally. According to the experimentalresults, the fatigue crack growth rate is related to the loading angle. Forthe same initial equivalent stress intensity factor (combination of thestress intensity factor in mode I and in mode II), the crack grows slowestunder pure mode I loading. The photos of crack bifurcation and the resultsof the crack growth rate in different specimens under different mixed-modeloadings are presented. Furthermore, a numerical model of fatigue crackpropagation is proposed on the basis of the experimental results to evaluatethe influences of loading mode on the crack growth rate. The validation ofthe model is performed on the steel specimens under mixed mode loading. Thenumerical evaluations are in good agreement with the experimental results.