Fatigue Crack Growth Modelling in Welded Stiffened Panels under Cyclic Tension

摘要

The influence of welding residual stresses in stiffened panels on effective stress intensity factor values and fatigue crack growth rate was studied in this paper.Interpretation of relevant effects on different length scales such as dislocation appearance and microstructural crack nucleation and propagation are taken into account using Molecular Dynamics (MD) simulations as well as a Tanaka-Mura approach for the analysis of the problem.Mode I stress intensity factors (SIF),KI,were calculated by the ANSYS program using shell elements and assuming plane stress conditions.The SIFs were calculated from FE results using the crack tip displacement extrapolation method.A total SIF value,Ktot,is contributed by the part due to the applied load Kapp,and by the part due to weld residual stresses,Kres.In the FE software package ANSYS the command INISTATE is used for defining the initial stress conditions.The FE analysis for the stiffened panel specimens showed that high tensile residual stresses in the vicinity of a stiffener significantly increase Kres and Ktot.Correspondingly,the simulated crack growth rate was higher in this region,which is in good agreement with experimental results.Compressive weld residual stresses between two stiffeners decreased the effective SIF value,Keff,which was considered as a crack growth driving force in a power law model.