Failure Analysis on Early Fracture of A356 Aluminium Support for B5 Rear Axle Assemble

Early fracture failure reasons of a A356 aluminium support for the B5 rear axle assemble during bench testing were analyzed by macro analysis, chemical compositions analysis and scanning electronic microscope observation. The results show that because the small pit defect caused by the accidental force at the place of the structural bead resulted in the stress concentration, the crack source appeared earlier in this area. At the same time, there was so much loose defect near the crack source that the crack developed quickly in fatigue form until fracture. At last improvement measures were proposed.