Failure Analysis of a High-Speed Shaft Crack

Failure analysis of a high-speed shaft in a reducer used to drive a diaphragm pump has been carried out. The shaft fractured in the keyway. Theoretical calculation, chemical analysis, micro-structural characterization, and finite element simulation were used for the analysis to determine the failure reasons and bring improved measures. The result shows that the chemical composition of materials, microstructure, and mechanical properties of the shaft and key meet the requirement; however, the improper design of the key and shaft causes stress concentration in the keyway, and the end of the keyway tends to crack. The fit between shaft and gear and the fit between key and shaft are too loose that they can cause fretting, which make the cracks to expand. In addition, several improved designs have been suggested and they prove to be effective after simulating.