Effect of Notch, Corrosion and Stress Ratio on the Constant and Variable Amplitude Fatigue Behavior of two Materials

The fatigue response of 7075-T73 aluminum alloy (cyclically hardening) and SAE 1045 (mod.) steel (cyclically softening) was investigated in air and corrosive environments under constant amplitude and variable amplitude fatigue loadings. Variable amplitude tests showed that crack propagation life was important in notched specimens in air as well as in corrosive environment. In corrosive environment pits were found to act as initiation sites in the steel specimens.

The effect of stress ratio, notches and environment on the fatigue life was treated through an effective stress, . Here, ‘m’ is a material constant that depends on the environment. This relation was also examined to predict fatigue lives under loading with variable stress ratio and applied to fatigue results.