Influence of shell dimensions and welding sequence on buckling behavior of welded shells

Welding, among all mechanical joining processes, has been employed at an increasing rate for its advantage in design flexibility, cost saving, reduced overall weight and enhanced structural performance. However, for structures made of relatively thin components, welding can introduce significant buckling distortion which causes loss of dimensional control, structural integrity and increased fabrication costs due to poor fit-up between panels. Different parameters can affect on buckling behavior of welded thin structures such as, heat input, welding sequence, dimension of structure etc.. In this work, 3-D thermo elastic-viscoplastic finite element analysis technique is applied to evaluate the effect of shell dimensions and welding sequences on buckling behavior of welded thin shells. To check the accuracy of the proposed method, a specimen was constructed with a length, width, radius and thickness of L=500, W= 500, R=1000, t= 1.5 mm, respectively. One side of shells was fixed and welding was started from free side, opposite side of fixture. This specimen was modeled by proposed FEM and the results were validated by designed experiment. The emphasis on the experimental part was to observe the behavior of welded shells during welding. Comparison between the results of experiment model and 3D-FEM shows that there is a good compatibility between the results. Therefore, the procedure presented here is suitable for estimating the behavior of specimen during welding. On the other hand, in present work, approximated longitudinal transient stresses which produced in each time step, is applied to 3D-eigenvalue analysis to ratify predicted buckling time and corresponding eigenmode. The results of finite element analysis shows that not only the size of length, span and thickness of welded thin shells but also welding sequences affect on the number of local buckling, mode shape of global buckling and post-buckling behavior of welded thin shells.