Volume 10, Issue 2 (March 1982)
The Effect of Varying Mean Stress on the Dimpled Loaded-Hole Fatigue Strength of 2024-T3 Aluminum Alloy
The effect of mean stress on the fatigue strength of notched and unnotched metal components is well known. Recently, a residual stress technique known as dimpling has been developed and used for improving the zero-to-tension fatigue strength of loaded holes in thin sheet material. Experiments were conducted to investigate the effect of varying stress ratio on the dimpled loaded-hole fatigue strength.
In tension-tension fatigue tests on nominally 1.6-mm thick 2024-T3 (Unified Numbering System [UNS] A92024) aluminum alloy specimens, dimpling gave fatigue strength improvement factors of 3.67, 2.78, and 1.5 at ratios of minimum to maximum stress of 0.0, 0.5, and 0.9, respectively, all at 107 cycles to failure. The strengthening effect of dimpling is found to decrease with decreasing life (higher maximum stress) and tends to become independent of stress ratio at low values of life.