SERVICE FAILURE INVESTIGATIONS.

In this paper various aspects of service failures and methods applied in the investigation of service failures have been described. From the case histories included in this paper, it may be concluded that fatigue cracking is a rather common cause of service failures. In the cases described fatigue cracks were initiated by either surface defects or by inclusions in the material. The surface defects consisted of decarburization, accidental removal of a hardened layer and insufficient surface quality as the result of bad workmanship during machining. The cases of brittle fracture described were the result of improper heat treatment which produced a brittle condition of the material. One of the failures described was the result of severe residual stresses induced during production which, in combination with stresses induced during further handling, caused fracture.