抄録
In this research, the effect of pre-fatigue on the impact tensile properties of the laser welded butt joint of high strength steel plates with tensile strength levels of 590MPa and 780MPa (denoted by HR590 and HR780, respectively) were investigated by the split Hopkinson bar apparatus. Quasi-static tensile tests were also performed to examine the effect of strain rate on the strength and the elongation. It was found that the effect of pre-fatigue on the tensile strength of welded butt joints is quite small if the applied stress in the pre-fatigue is less than the apparent yield stress of the welded butt joints. In the results of impact tensile tests for the welded butt joint of HR780 steel, however, the fracture strain of the specimens subjected to high cycle pre-fatigue was smaller than that of the virgin specimens. This may be caused by interaction of a number of cracks introduced by pre-fatigue with high strain rate.
