Analysis of quality defects in the fracture surface of fracture splitting connecting rod based on three-dimensional crack growth

Quality defects of fracture surface are easily produced in the fracture splitting process of connecting rod. At present, the resulting mechanism of this type of defect is lacking in evidence and there is no effective control method. Based on fracture mechanics and the actual production, this study simulates the process of connecting rod fracture splitting using finite element method. Three-dimensional crack propagation state is described, and the stress and deformation of the crack tip are analyzed. The essence of the fracture surface defects, such as drop-dregs, steps, and crack bifurcations, are mainly due to the change of the crack path and structure during crack propagation. These defects mainly occur at the boundary positions of the fracture surface such as bolt hole and end faces, which is due to the boundary’s stress and deformation characteristics of the fracture surface. The boundary is in the plane stress state, the crack tip undergoes shear deformation and has a large plastic zone which leads to severe twist of the crack tip opening angle. That causes the crack propagation path to be twisted and bent, thus resulting in fracture-splitting defects. Keywords: Connecting rod fracture splitting, Quality defects of fracture surface, Crack propagation state, The crack tip opening angle, The stress and deformatio