Welding-induced buckling prediction for large thin-walled cylindrical structures with non-uniform stress fields by friction stir welding

Abstract

The non-uniform welding stress distribution in large thin-walled cylindrical structures easily causes the buckling distortion due to weak structural stiffness and nonlinear geometric deformation. The non-uniform temperature field model induced by friction stir welding is analytically developed and is used to theoretically deduce the non-uniform stress model in the weld region. Both the two models are verified by the experimental data. A prediction model of critical buckling load is established for large thin-walled cylindrical structures considering the non-uniform welding stress distribution. The deflection function for buckling analysis is developed by using polynomials and the Chebyshev polynomials of the first kind that satisfy the boundary conditions along the four edges of the structure. The critical buckling loads are calculated for various cylindrical welded shell structures, which obviously decrease with the increase of the diameter-thickness ratio and the length-diameter ratio. The mitigation of buckling distortion is achieved by the correlation of the buckling load and the welding stress with various welding process parameters. The results are beneficial for the determination of geometric configuration and welding process parameters for large thin-walled cylindrical structures in fabrication of propellant tanks of launch vehicles.