Abstract: The initial fracture splitting process of rear axles’ main reducer shell bearing seats was simulated by ABAQUS and a numerical analysis was carried out. The material of the shell bearing seats is QT450 with 50% pearlite in the matrix structure. The position of the starting cracking point was determined by J integral， and the splitting force was then calculated. The plastic deformation of the crack tip region when cracking and its effect on the loss of circle were analyzed， and an experimental study was conducted. The results show that the starting cracking point of the bearing is located near the middle of the crack tip. The plastic area located at the root of the crack tip is of butterfly-shaped distribution， resulting in the small loss of circle of bearing holes. The processing quality of fracture splitting is qualified， which is suitable for the application of fracture splitting technology.The research result lays a solid theoretical foundation for improving the production process of shell bearing seats， and provides a reference for the selection of splitting materials of shell bearing seats， the design of splitting equipment and the formulation of processing procedures.

Key words: shell bearing seat, QT450, fracture splitting process, J integral, numerical analysis