K-calibration of special specimens for mode II, III and II + III crack growth

An original testing setup has been designed for generating pure remote mode II, III and mixed mode II + III crack propagation in a single cylindrical specimen with circumferential crack. This specimen is currently used for investigations of a shear mode fatigue crack propagation. The aim of this work was to perform the K-calibration of above mentioned specimens that will be used for a description of stability and growth of shear-mode fatigue cracks in the near-threshold region. Two-step submodelling based on the ANSYS code was performed in order to obtain sufficiently precise values of the stress intensity factors KII, KIII and KII,III along the crack front of small and large samples. The shape functions FII, FIII and FII,III were determined using the J-integral concept. The calculated values of the KIII factors could be, unlike those of KII factors, nearly compared with the solution based on an asymptotic approximation available in the literature. Calculations revealed that, for small gripping distances, the shape functions FII and FIII depend on the experimental adjustment of the gripping distance.