Abstract
This study was aimed at establishment of a model that can predict tensile shear strength and fracture portion of laser-welded lap joints in the tensile test. To clear the influence of bead length and bead width on them, the joints employed steel sheets with a thickness in the range of 0.8mm to 1.2mm were evaluated. It was found that the tensile shear strength increases with the bead size, and the fracture occurres at base metal (BM), weld metal (WM) or portion between them with a curvature (HAZ), in the tensile test. Also to clarify rotational deformation process around WM during the tensile test, cross-sections of joints were observed, which were applied to several loads in the tensile test. This observation derived relationship between the radius, Ri, at the inner plane of HAZ and the rotational angle, θ, of the center of sheet thickness. Furthermore relationship between Ri and applied load was obtained by linear regression. A plastic analysis for deformation of the joints was carried out based on these functions and some assumptions. These assumtions consider that the joint consists of BM, WM and HAZ, which are under simplified stress mode respectively. Finally estimation of the tensile shear strength and the fracture portion of the joints was achieved. This estimation made a good accordance with the experimental results.
