This study develops a new method for fatigue crack growth analysis at microstructure scale. Proposed model was constructed based on material anisotropic and crystallographic planes. Firstly the material behaviour at microstructure scale is anisotropic, which results in different stress and deformation fields around the crack tip. Secondly, cracks propagate along the distinct, which means, they are often angled cracks not on a plane normal to the major principal stress. In this research it has been attempted to suggest an accurate criterion for predicting the crack growth path at microstructure scales by investigating various criteria for crack growth. For this purpose with considering criteria such as fracture energy for transgranular and intergranular and also dominant slip plains, a criterion has been proposed to predict crack growth. Two different alloys, single-phase and two-phase, have been examined. Two different tests have been done upon those alloys, and the real path of the crack growth has been obtained in a specific area of these two specimens. Then, by modelling parts of tested piece through finite element software (ABAQUS) and by using extended finite element way, which has eliminated the need to remeshing in fracture mechanics problems, various criteria such as proposed criterion for predicting crack growth path are studied. The microstructures of both specimens tested in considered area were modelled as anisotropic and their crystal`s orientation was gain using EBSP method. The results suggest correctness of proposed criterion with less fault in single-phase alloys and acceptable fault in two-phase alloys.

Keywords