Evaluation of small fatigue crack deflection behavior on copper using electron backscatter diffraction and crystal plasticity finite element analysis

In this study, it was conducted to observe the propagation behavior of small fatigue cracks generated on the surface of alpha-brass and pure copper, using an electrodynamic plane bending fatigue testing machine. The EBSD method was also used to analyze the crystal orientation near the bottom of the notch on the surface of the test piece. For each slip system of the grain, we calculated the slip factor, defined as the ratio of resolved shear stresses that considers the singular stress field at the crack tip, and investigated the relationship between the propagation behavior of small cracks and the slip factor. Furthermore, we performed a crystal plasticity finite element analysis (CP-FEM) using a crystal plasticity FEM model created from the grains obtained by the EBSD method to predict the deflection behavior of small fatigue cracks when propagating through the grain boundaries. The results indicated that when a crack propagates across a grain boundary, it is difficult to predict the deflection behavior using slip factors, however, the deflection behavior of a crack can be predicted from the resolved shear stress calculated using CP-FEM, which considers the mechanical interactions between crystal grains.