IMPACT TENSILE PROPERTIES OF YAG LASER WELDED BUTT JOINTS MADE BY DIFFERENT STEEL SHEETS FOR VEHICLES

The tensile properties of YAG laser welded butt joints using different high strength steel sheets with a tensile strength of 270 MPa, 590 MPa and 980 MPa (denoted HR270, HR590 and HR980, respectively) were investigated at static and dynamic rates, together with the three kinds of laser welded joints made by the same steel sheets. The impact tensile tests were performed by using the vertical type of split Hopkinson tension bar apparatus, while the static tensile tests were carried out using a universal testing machine INSTRON5586. The impact tensile strengths were significantly increased in comparison with the static ones due to the effect of strain rate, which might be the contribution of the part of HR270 base metal. And in both of static and impact tests, the fracture strains of HR270-HR590 joint, HR270-HR980 joint and HR590-HR980 joint were about one half of the fracture strains observed in the same steel welded joints of HR270-HR270, HR270-HR270 and HR590-HR590, respectively.