Effect of Slip Ratio on Driving Forces of Short Cracks at Inclusions in ContactFatigue

摘要

Inclusions in hard steels are one important cause of damage under contractfatigue loading conditions such as in bearings or on gear wheel flanks. The inclusions act as fatigue crack nuclii. Under contact fatigue loading the inclusions can initiate so called butterfly cracks which are inclinded some 45 deg. to the loading raceway. The paper deals with the effect of sliding ratios action on the raceway on the driving forces of the short cracks. Substantial sliding ratios can be obtained eg. on gear wheel flanks away from the operating pitch diameter. Manganese sulfide, alumina and titanium nitride inclusions are considered. The simulations are states with a heat treatment operation corresponding to the hardening of the steel. The different thermal contractions of inclusion and matrix during cooling after austenitisation are considered.