Failure analysis of an input shaft of skip drive gearbox

The present paper deals with the failure analysis of an input shaft of skip drive gearbox, which had failed after 13 months of service against an expected life of 15 years. Evidences suggest that the input shaft has failed by stress corrosion cracking (SCC). After initiation at the keyway edges, the cracks have propagated progressively along the circumference of the fillet. Once the cross section of the shaft reduced below the critical limit, it has failed by sudden torsional overload. Investigation revealed that use of improper steel with high amount of MnS was responsible for the SCC.