Influence of Stress Change on the Fatigue Behavior and Fatigue Life of Aluminum Oxide-Dispersion-Strengthening Copper Alloy at Room Temperature and 350
Norio KAWAGOISHI, Hironobu NISITANI, Eiji KONDO, Atsunori SHIMAMOTO and Rieko TASHIRO
Abstract:In order to investigate the influence of stress change on the fatigue behavior and fatigue life of an aluminum oxide-dispersion-strengthening copper alloy at elevated temperature, rotating bending fatigue tests were carried out under two-step loading at room temperature and 350. Both of static strength and fatigue strength decreased at 350. However, at the same relative stress a/B, fatigue life was longer at 350 than at room temperature. Although the cumulative ratios (N/Nf) were nearly unity for both the low to high and the high to low block loadings at room temperature, Miner's rule did not hold at 350. These results were related to the stress dependence on the log l - N/Nf relation. That is, the crack length initiated at the same N/Nf was larger in higher stress level at 350, whereas there was no stress dependence in the relation at room temperature. The stress dependence on the relation at 350 was caused by the suppression of crack initiation due to the surface oxidation. Key Words:Fatigue, Aluminum oxide-dispersion-strengthening copper alloy, Elevated temperature, Two-step loading, Crack initiation, Crack propagation