Effect of specimen width on the failure behavior in resistance spot weld tensile shear testing

Abstract

Specimen dimensions have significant effect on the tensile shear strength (TSS) of resistance spot welds (RSW) in the commonly employed tensile shear testing. Minimum required dimensions specified in different industrial test standards vary somewhat however. In this paper, the most influential dimension, the tensile shear test specimen width, is investigated for a low-strength steel (galvanized steel Q235), a high-strength steel (TRIP980), and aluminum alloy 5052. The relationships between the specimen width and weld properties, such as TSS, energy absorption, and failure modes, were investigated experimentally. The results show that there is a critical width of the specimen beyond which the TSS of the RSW maintains a constant value and the failure is at the spot weld. This constant TSS is a saturated value. The perceived TSS from the tensile shear testing is lower than the saturated TSS when the width is smaller than the critical value. The displacement at the TSS and the energy up to failure from the tensile shear testing, however, shows opposite trend due to the large plastic deformation from the base sheet metal in narrower specimens. From the results, a minimum width of tensile shear test specimen for determining saturated TSS is recommended.