変動荷重ΔＫ減少試験法による疲労き裂伝ぱ機構の研究

Abstract

In order to predict the most reliable fatigue life under variable loading conditions such as survice environments, a new fatigue test method was developed, and by using it the fatigue crack propagation properties were studied for HT80, SM50B and SUS 304 steels.The test results show that, although no crack closure occurred in both the variable and constant loading tests, the crack propagation rate under the variable loading test condition was much faster than that under the constant loading test condition for all tested alloys especially at low ΔK regions.The maximum acceleration of the crack propagation was dependent of the variable loading amplitude. When the variable load was frequently applied, the crack propagation rate became proportional to second power of ΔK.From these results, it can be said that the new fatigue test method is one of the best methods to predict the most reliable fatigue life under variable loading conditions.