Analysis of Residual Stress in Arc Welded Lap Joints of High Strength Steel Sheets and Welding Wire Using Material Properties during Heating and Cooling

An approach for the precise analysis of residual stress in arc welded lap joints of high strength steel sheets is proposed. This approach involves the development of a method for measuring material properties during both the heating and cooling processes. The measured material properties are then utilized in a thermal elastic-plastic finite element method (FEM) analysis of the welding residual stresses in the lap joints. Analysis accuracy is investigated by comparing the results using material properties measured during heating, cooling, or both. The maximum temperature distribution on the surface of the heat affected zone (HAZ) is measured and accurately predicted by a welding thermal conduction analysis. When the material properties measured only during heating, only during cooling, or during both heating and cooling were used in the thermal elastic-plastic FEM analysis, the results showed that the stress histories in arc welded joints of 780 MPa high strength steel sheets are different. The analyzed residual stress using the material properties measured during cooling is closer to that obtained using the properties measured during both heating and cooling. This result suggests that consideration of the cooling phase is crucial for accurately predicting the residual stress distribution in lap joints. When a narrow specimen for the tensile-shear strength test is cut from a specimen from the original welded joint, the analysis and measurement confirm that the maximum longitudinal tensile residual stress in the original arc welded lap joint is significantly reduced by approximately 44 %. Notable changes in the distribution characteristics of the transverse residual stress were also observed. These findings emphasize the importance of incorporating both heating and cooling material properties in analyses of welding residual stresses in arc welded lap joints.