An experimental investigation on critical specimen sizes of high strength steels DP600 in resistance spot welding

Because of good combination of high strength and ductility, high strength steels (HSS) have been increasingly utilized by automotive companies, especially the DP steels. In the present paper, different weld length of the elliptical nugget for DP600 resistance spot welding was realized through modified electrode tips. Then the relationship between the weld length and critical specimen sizes, including specimen width and sheet thickness, was investigated through analyzing the failure modes in tensile-shear testing using statistical method. The results showed that the weld length, specimen width and sheet thickness had great effect on the failure modes of tensile testing specimen. And the critical specimen width, sheet thickness and tensile-shear strength were all linearly increased with weld length. The research results can provide a guideline for tensile-shear testing analysis and for spot welds structure design.