Effect of residual stress shakedown on stiffened plate strength and behaviour

Numerical simulation is used to study the influence of welding-induced residual stress in welded, tee-stiffened plates focusing on the effect of shakedown. Welding is simulated using 3D thermo-elasto-plastic finite element analysis. The influence of strain hardening and number of load cycles on residual stress shakedown is then investigated. Load versus end-shortening curves are used to characterise the strength and behaviour of stiffened plates under axial compression both before and after shakedown. Results show that the reduction in residual stress due to shakedown occurs entirely during the first load cycle provided that the magnitude of that load is not subsequently exceeded. Both the tensile and compressive welding residual stresses in the plates are reduced by as much as 40% when the applied load causes an average stress equal to 50% of the yield stress. This level of shakedown increased the ultimate strength of tee-stiffened plates by as much as 6% in some cases, but the potential for increase in ultimate strength as a consequence of shakedown was found to depend on the failure mode.