Paper Title
STRESS INTENSITY FACTORS AT TORTUOUS CRACK FRONTS UNDER SHEAR LOADING

Abstract
The aim of the research was to compare the stress-strain state at the crack front for planar cracks and tortuous ones under fatigue mode II loading. The fronts of fatigue cracks in metallic materials are usually tortuous due to microstructural heterogeneities. However, the stress intensity factors (SIFs) that describe the stress-strain state at the crack front under linear-elastic conditions are calculated using standardized fracture mechanics models where plane cracks and straight crack fronts are assumed. Our previous calculations for cracks with in-plane tortuosity under fatigue mode III loading revealed that the local SIFs k1, k2, and k3 appear along the crack front. The calculated local SIF k2 was high enough to propagate mode II under remote mode III loading. In this study, the compact tension shear specimen(CTS) with the tortuous crack under pure remote mode II loading was used to calculate local SIFs using the finite element method. The changes in local and global SIFs with respect to those for a smooth front are presented separately for in-plane and out-of-plane tortuous crack fronts and, on the global level, for their combination. At the in-plane serrated crack fronts, local k3 values appeared and local k1-values were present for the out-of-plane roughness. For equal levels of remote mode II loading, a geometrical shielding effect induced by the crack tortuosity, i.e. a decrease of the averaged values of local mode II components with increasing roughness of the crack front, was revealed. These changes in local SIFs can be, for example, used to correct the experimental values of the effective fatigue thresholds in metallic materials obtained under the assumption of straight crack fronts. Keywords - Compact-tension-shear specimen, Remote mode II loading, Geometrical shielding effects.