Abstract
In this research, fatigue strength improvement method which combined cleaning treatment with a grinder and hammer peening treatment is investigated. The condition of the hammer peening treatment is determined by hardness and surface texture. The improvement effect on both fatigue crack initiation life and the fatigue crack propagation life is clarified from the fatigue test with the out-of-plane gusset joint and its improvement mechanism is discussed from the view points of stress concentration and residual stress. The retardation effect of crack propagation due to the compressive residual stress, which is induced by the peening treatment, exists even if the fatigue crack propagates into the region where the tensile residual stress had originally existed. The proposed method can improve both the fatigue crack initiation life and the fatigue crack propagation life.
