Cause Analysis on Cracking of Bridge Swing Arm of a Heavy Vehicle

The bridge swing arm of a heavy vehicle cracked in service. By means of macro examination, chemical composition analysis, micro analysis and metallographic examination, the cracking causes of the swing arm were analyzed. The results show that the cracking mode of the cracked swing arm was fatigue cracking. During the forging process, the swing arm had folding defects. The folding defects were accompanied by inclusions and microcracks. Under the working stress, the folding defects became the fatigue source, which eventually led to the swing arm cracking.