Study on Joint Residual Stress Induced by Laser Beam Welding of High Strength Automobile Thin Sheet

Despite the advantages of the high energy density, high welding velocity and low deformation, some detrimental residual stresses were still introduced during the laser beam welding (LBW) process. The aim of this work was to study the magnitude and distribution of the residual stress in the LBW seam of the high strength automobile thin sheet. With the feature of applicable to the measurement of the residual stresses in the narrow area, the indentation strain method (ISM) was employed. By appropriate design of the biaxial strain rosette with the small size, the ISM was successfully used to measure the residual stress in the thin sheet LBW seam. Also, the finite element method (FEM) was used to calculate the residual stress. The comparison of the measured residual stresses through the ISM was made with those of the cutting relaxation method (CRM) as well as the FEM results. The ISM results showed that the highest tensile residual stress located at the seam centerline and exceeded to the 60 percent of the yield strength of the base metal.