Distribution of Residual Stress in the Vicinity of Fatigue Crack Tip and Crack Growth

The distributions of residual stress in the vicinities of fatigue crack tips and behind them were measured in various conditions of crack length, stress amplitude and stress ratio by the counter method for X-ray microbeam stress measurement. On the basis of the distributions of residual stress, the crack closure behavior was examined analytically by the finite element method and the correlation between the crack growth and the distribution of residual stress was discussed. It was found that the distribution of residual stress in the vicinity of the crack tip was affected by the crack length and the loading conditions. The plastic zone size ahead of the crack tip was related to the maximum applied stress and the crack length, and it was evaluated from the maximum stress intensity factor K_max. The crack growth rate was expressed in terms of the effective stress intensity range that was calculated by the finite element method based on the distribu-tion of residual stress. It is considered that the crack growth behavior is closely related to the distribution of residual stress, and the crack growth rates can be predicted from the effective stress intensity range ΔK_effcalculated by taking account of the distributions.