Improvement Effects of Fatigue Strength by Burr Grinding and Hammer Peening Under Variable Amplitude Loading

Abstract

This study investigates improvement effects of fatigue strength by burr grinding and hammer peening treatments. High-cycle fatigue tests with constant and variable amplitude loadings are performed on out-of-plane gusset plate specimens. Test results indicate that the reduction of stress concentration by the burr grinding greatly improves the fatigue life under both the constant and variable amplitude loadings. For the variable amplitude loading, the damage accumulation D obtained by Miner’s rule with the mean curve of constant amplitude loading is conservative (D > 1.5). However, under the variable amplitude loading, since the beneficial effects of the peening treatment on the fatigue life decrease due to the relaxation of compressive residual stress, the damage accumulations in specimens prepared by cleaning and subsequent hammer peening are extremely non-conservative (D ≈ 0.2). In addition, the stress patterns do not affect the fatigue life significantly.