Experimental and numerical studies of residual stress of high strength steel T/Y-joints

An investigation on the residual stress distributions near the weld toe of HSS plate-to-plate T and Y-joints is carried out. Two groups of specimens, corresponding to welding preformed at ambient temperature and at a preheating temperature of 100°C, are fabricated. The effects of preheating and joint geometry on the residual stress distribution near the weld toe are investigated by applying the standard ASTM hole-drilling method for residual stress measurement. Furthermore, a preliminary study is also performed to evaluate the influence of brace plate cutting on the residual stress distribution near the weld toe of the joints. After that, a carefully sequentially coupled thermal-mechanical modelling procedure was developed for residual stress analysis for the HSS plate-to-plate joints. Both 2D and 3D models are created to investigate the residual stress distribution in the HSS plate-to-plate joints. A small scale parametric study is carried out to investigate the influence of some key welding parameters such as the boundary condition, the preheating temperature, the number of welding pass, the welding speed and the welding sequence on the magnitude and distribution of residual stress. It is found that while transverse residual stress with magnitude as high as one third of the yield strength of HSS could appear near the weld toe of the joint, proper preheating could significantly reduce the magnitude of the residual stress. Besides the investigation for the residual stress in the HSS plate-to-plate T and Y-joints, the study for welding residual stress in box HSS T-joints is also included. Two box HSS T-joints with the same geometrical size are fabricated to investigate the welding residual stress distributions of HSS box joints. One specimen is welded at ambient temperature while the other one is preheated to 100°C before the welding. It is found that the residual stress at chord weld toe along the surfaces parallel to chord length are generally smaller than along the surfaces perpendicular with chord length.Doctor of Philosophy (CEE