Dynamic tensile behaviors of welded steel joint material

Q355 structural steel has been widely used in the construction industry. A typical Q355 welded steel joint consists of three portions, i.e. Q355 base metal material, heat affected zone (HAZ) material and weld metal material. Although the static material properties of the Q355 base metal and weld metal have been intensively investigated, the dynamic material properties of Q355 base metal, HAZ and weld metal are not well understood yet. The lack of understanding of the strain rate effect on the base metal, HAZ and weld metal material may lead to improper design of welded steel structure against dynamic loading. In this study, quasi-static and dynamic tensile tests on the widely used Q355 base metal, HAZ and weld metal materials were carried out to study their material properties with the strain rate up to 234.90 s−1. The failure modes were investigated and compared with the aid of scanning electron microscope (SEM) images. The strain rate effects on the tensile strength, failure strain and elastic modulus of base metal, HAZ and weld metal materials were revealed. With the testing data, empirical formulae based on the Cowper-Symonds model and Johnson-Cook model were fitted by incorporating the dynamic increase factors (DIFs) of tensile strength and dynamic stress flow, respectively. The proposed empirical formulae can be used in numerical modelling of welded steel structures under dynamic loading.