Subsurface Crack Propagation in Rolling Contact Fatigue of Sintered Alloy

摘要

Rolling contact fatigue tests of sintered alloy were carried out under two cylinder contacts. Damage of the specimen was detected by using acceleration sensor before occurrence of final failure, namely spalling failure. In order to study the damage process of contact fatigue of sintered alloy, surfaces and cross sections of the specimens were observed after contact fatigue test. Damage on the specimen surface such as pitting mode of failure was not observed, while subsurface crack initiation and propagation were dominantly observed. Subsurface crack length increased with increasing number of cycles. Crack initiation and propagation in the subsurface of the specimen will be followed by a spalling mode of fracture. Stress distribution near the contact region was estimated by FEM (Finite Element Method) analysis. The location of the maximum shear stress range estimated by FEM analysis coincided with the depth of the crack initiation point observed in experiment. The position at the maximum shear stress range approaches to the specimen surface with an increase in tangential force. Subsurface crack growth behavior was controlled by the shear stress intensity factor range, ΔK_(II).