Experimental research and numerical analysis of welding residual stress of butt welded joint of thick steel plate

The thickness of steel plates used in the member has gradually increased to meet the load-bearing capacity requirements of long-span steel bridges. As the primary connection method of thick steel plate, welding will result in considerable welding residual stress with complex distribution. Large welding residual stress will significantly impact the performance of steel bridges. In this paper, the distribution of residual stress in welded thick steel plate is systematically studied, a specimen with a thickness of 80 mm was designed and fabricated, and the welding residual stress was measured by X-ray diffraction. The finite element model was established and verified by test results. Subsequently, the finite element calculation of the welding residual stress of steel plates with thicknesses of 20, 40, 60, 80, and 100 mm was carried out, and the distribution of surface residual stress and the influence of plate thickness on residual surface stress were studied; then the spatial evolution mechanism of welding residual stress was studied, and the distribution of residual stress inside steel plate and the influence of plate thickness on the distribution of residual stress were revealed. The results show that the surface and internal residual stresses of 20-100 mm thick plates have good symmetry on the paths perpendicular to the weld seam, and asymmetry only occurs in the weld seam and heat-affected zone where the stress fluctuates. On the paths perpendicular to the weld seam, the stress in the X direction transitions from the "M" shape distribution on the surface to the "pi" shape distribution inside for 20-40 mm thick plates, and the residual stress near the weld seam gradually changes from compressive to tensile; The distribution of stress in the X direction in the 80-100 mm thick plate has experienced the transition from "M" shape to "pi" shape to "M" shape, and the stress near the weld seam has experienced the transition from compressive to tensile to compressive. The stress change in the X direction of the 60 mm thick plate is between the above two cases. On the path of internal stress along the thickness, the maximum stress in the X direction is 310-400 MPa for 20-40 mm thick plates, which appears at about 1/2 plate thickness. The maximum stress in the X direction for 60-100 mm thick plates is 400-480 MPa, which appears at 0.2-0.3 times the thickness of the plate from the upper surface. The results could serve as a reference for welding residual stress analysis and guide optimization design of steel bridges made of thick steel plate.