Branched crack initiation and propagation under inclined loading for an austenitic stainless steel

In this work, a proper type of circular ring specimen containing a V-notch on the internal radius has been used to realize mixed-mode stress field at notch root under inclined uniaxial loading. Not only crack initiation and propagation behavior from a notch for a 304L austenitic steel was investigated, but also crack arrest and branch phenomena were analyzed with respect to the change of the angle of inclined loading. The relationship between the angle of inclined loading and the angle of branched crack was studied. The microstructure of branched cracks was observed, and the tensile stress model and the energy release rate model were applied to identify the crack growing direction. When the far-field cyclic loading changes an angle during the test, the fatigue crack growing will arrest, and a great number of cycles are necessary to initiate a new crack from the former crack. The direction of the new crack propagation is determined by mixed mode conditions.