Influence of welding residual stress in fatigue crack growth of 7N01 aluminum alloy

Welding residual stress affects crack propagation as an average stress. Residual stress was separated from the average load stress. By constructing a typical welding residual stress field, the stress intensity factor of the welding residual stress field was calculated with the extended finite element method. The fatigue expansion test of the compact tensile (CT) specimen was carried out. Based on the Walker formula, the average stress intensity factor K_m (static amount) at the crack tip and the magnitudeΔK (dynamic amount) of the stress intensity factor were separated to obtain the nonlinear relationship between da/dN versus K_m andΔK. The results showed that the stress ratio was nonlinear with the crack length under different external loads and the residual stress had a scale effect on crack propagation. When the crack length of CT specimen was less than 2 mm, the residual stress field obviously affected the fatigue crack growth rate while the external load was the dominant factor, when the crack length of CT specimen was more than 2 mm.