Effect of Post-Weld Heat Treatment on the Plastic Buckling of Welded Cylindrical Shells

Storage tanks, silos and other welded cylindrical shell structures are usually constructed of rolled panels which are joined by patterned circumferential and longitudinal welds. Cold-formed residual stresses are produced during the cold bending process of steel panels, and obvious deformations and uneven distributed welding residual stresses are also produced because of the welding process. Studies have shown that residual stresses could weaken the critical buckling load of welded cylindrical shells under axial compression. Stress-relief post-weld heat treatment (PWHT) is a process that heats the workpiece gradually to 500∼650 °C, holding the temperature 0.5 hours then reducing the temperature slowly. Two cylindrical shell specimens are fabricated in this paper, and one is processed with stress-relief PWHT, while the other is not. The magnitude and distribution of residual stresses near the weld zone in each specimen are measured with an X-ray diffraction-based measurement system (named iXRD by the manufacturer), and initial imperfections and critical load of the specimens are obtained by the use of an axial buckling experiment platform. Thereafter, numerical simulations are conducted with measured geometric imperfections and residual stresses exerted into the finite element model. Finally, comparison of the critical loads of both cylindrical shell specimens is made, showing the effects of residual stresses on the plastic buckling of cylindrical shells under axial compression.