Avaria by the bottom of a bolt on a diesel of engine

Abstract

A drive from a diesel engine of a truck was broken into four parts during normal use. Damaged bolt caused longitudinal and transverse cracks. They started from the surface of the hole and stretched outward. The appearance of marginal signs and striations on the surfaces of all regions of origin of the crack indicate that fatigue breakage is the dominant damaging mechanism of the bolt. The surface of the hole and the outer surface are indicated to be cemented. Microstructure and microstructure profiles at the bolt surface and in the regions of the hole surface were examined to determine the thickness of the cementitious layer. However, not only there was no cementitious layer found on the surface of the hole, but also a serious decarburization occurred in the area. The appearance of decaying the surface of the hole greatly decreases the fatigue strength of this area, so the crack has started from the surface of the hole and stretched to the outer circle, eventually opening the tear. Inappropriate cementing technology is responsible for decarburation of the surface of the hole.