Multiscale fatigue crack growth modelling for welded stiffened panels

The influence of welding residual stresses in stiffened panels on effective stress intensity factor (SIF) values and fatigue crack growth rate is studied in this paper. Interpretation of relevant effects on different length scales such as dislocation appearance and microstructural crack nucleation and propagation is taken into account using molecular dynamics simulations as well as a Tanaka-Mura approach for the analysis of the problem. Mode I SIFs, K-I, were calculated by the finite element method using shell elements and the crack tip displacement extrapolation technique. The total SIF value, K-tot, is derived by a part due to the applied load, K-appl, and by a part due to welding residual stresses, K-res. Fatigue crack propagation simulations based on power law models showed that high tensile residual stresses in the vicinity of a stiffener significantly increase the crack growth rate, which is in good agreement with experimental results.