FAILURE ANALYSIS OF THE AUTOMOTIVE REAR AXLE

The automotive rear axle welded by several parts was fractured after 790 000 km running. Macro-examination,microstructure examination,chemical composition analysis,and fracture analysis were carried out on the failure rear axle and the results showed that failure of the rear axle is fatigue fracture. Because of local stress concentration caused by the size difference of the two welded parts,welding stress of the heat-affected zone and the weakness of the Widmanstaten structure,cracking source were produced at the heat-affected zone,which led to the final fatigue fracture of the rear axle when the automobile bumped and shake.