Failure analysis of a sugarcane loader rear shaft

This work deals with the failure analysis of rear differential shaft of a sugarcane loader that broke in less than a year of use. For the analysis of fracture, fracture surface macrographs, microhardness profile and metallographic analysis were realized. It was also carried out a numerical simulation of shaft estimating the external stresses applied during use. The numerical simulation was performed in linear elastic regime. The microstructure on the surface is composed of martensite and ferrite caused by the superficial hardening heat treatment and in the core formed by perlite and ferrite. The microhardness profile showed a hardness peak of 648 HV in the peripheral region of the shaft. From the analysis of the fracture surface it was possible to observe that the failure occurred in unidirectional fatigue of high cycle, and we observed several ratchet marks along the rounding radius of the shaft. The numerical simulation permitted to quantify the stresses and showed that rounding radius in the shaft base was the cause of failure.