Influence of Stress Change on the Fatigue Behavior and Fatigue Life of Aluminum Oxide-Dispersion-Strengthening Copper Alloy at Room Temperature and 350°C

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°C. Both of static strength and fatigue strength decreased at 350°C. However, at the same relative stress σ_a, /σ_B, fatigue life was longer at 350°C than at room temperature. Although the cumulative ratios Σ (N/N_f) 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°C. These results were related to the stress dependence on the log l-N/N_f relation. That is, the crack length initiated at the same N/N_f was larger in higher stress level at 350°C, whereas there was no stress dependence in the relation at room temperature. The stress dependence on the relation at 350°C was caused by the suppression of crack initiation due to the surface oxidation.