The Role of Crack Closure in the Fatigue Threshold at Elevated Temperatures

Abstract

fatigue crack growth and the threshold of SS41, SM41A, and SUS304 steels and 2218-T6 Al alloy were examined at elevated temperatures up to 500°C. An emphasis was made on examining the role of crack closure in the fatigue threshold at elevated temperatures. Fatigue threshold, ΔK_th, was found to increase with an increase in test temperatures for all the steels tested, while it was found to decrease for the 2218-T6 Al alloy. Oxide-induced crack closure was found to play an important role in the temperature dependence of ΔK_th for SM41A and 2218-T6 Al alloy, while it was found to play a less important role in the increase in ΔK_th at elevated temperatures for SS41 and SUS304 steels. The importance of the relative value of the oxide thickness to the CTOD at threshold was discussed.