Analysis on Cracking Reason of Bearing Gear Ring

A bearing gear ring was broken after using about four years. By means of chemical composition analysis, mechanical property testing, macro and micro examination, the cracking reason of the bearing gear ring was analyzed. The results showed that the microcrack was formed at the etch pit of bolt hole inner surface, and the yield strength of gear ring was lower than specification, and the alternate stresses existed in the service process which caused the fatigue failure.