超硬合金の微小疲労き裂進展挙動に及ぼす応力比の影響

抄録

Four point bending fatigue tests were performed on cemented carbides to investigate an effect of stress ratio on the short fatigue crack growth behavior in air. At the region of high crack growth rates, the maximum stress intensity factor, K_max, is a dominating factor for crack growth behavior, while at the region of low crack growth rates, stress intensity factor range, ΔK accelerates the crack growth rates with the aid of the maximum stress intensity factor, K_max. The enhanced crack growth rate brought by cyclic stressing at the low K_max region is expected to be concerned with cyclic fatigue damages ; i.e., loosening of a interface between WC grain and binder phase ahead of the crack tip, and also removal of bridging parts at the crack wake.