Abstract
Fatigue crack propagation law in the following two cases was investigated under the negative stress ratio R(=σmin/σmax) condition. The one is the crack propagation in the field of welding-residual stress, and the other is that after the overloading. In the former case, the crack propagation rate da/dN depended on the stress ratio R. Due to the tensile residual stress, the crack propagation rate increased as the stress ratio decreased in the range of 0≤R≤-2. In the latter case, the crack propagation rate da/dN after the overloading was higher at first and then became lower than that of the constant stress amplitude. In the present experimental cases, the crack propagation rate was affected by the residual stress and the overloading. However, the crack propagation behavior had a good correlation with the crack closure behavior. Therefore, in the present cases, the crack propagation law was reasonably evaluated with the effective stress intensity factor range ΔKeff.
