Effect of stress ratio on fatigue lifetime and crackgrowth behavior ofWC-Co cemented carbide
(1. Department of Mechanical Engineering, University of Toyama, Toyama 938-8601, Japan;
2. Machinery and Engineering Group, YKK Corporation, Toyama 930-8555, Japan;
3. National Institute of Technology, Toyama College, Toyama 939-8630, Japan)
2. Machinery and Engineering Group, YKK Corporation, Toyama 930-8555, Japan;
3. National Institute of Technology, Toyama College, Toyama 939-8630, Japan)
Abstract: Two types of fatigue tests, a rotating bending fatigue test and a three- or four-point bending fatigue test, were carried out on a finegrained WC-Co cemented carbide to evaluate its fatigue crackgrowth behavior and fatigue lifetime. From successive observations of the specimen surface during the fatigue process, it was revealed that most of the fatigue lifetime of the tested WC-Co cemented carbide was occupied with crackgrowth cycles. Using the basic equation of fracture mechanics, the relationship between the fatigue crackgrowth rate (da/dN) and the maximum stress intensity factor (Kmax) was derived. From this relation, both the values of the threshold intensity factor (Kth) and the fatigue fracture toughness (Kfc) of the material were determined. The fatigue lifetime of the WC-Co cemented carbide was estimated by analysis based on the modified linear elastic fracture mechanics approach.Good agreement between the estimated and experimental fatigue lifetimes was confirmed.
Key words: WC-Co cemented carbides; fatigue lifetime; crackgrowth rate; stress intensity factor