Experimental study on fatigue performance of high strength steel welded joints

The welded joint of steel structure is prone to occur fatigue fracture under dynamic loads. In this paper, an experimental study on the fatigue performance of base material, butt weld, and cross fillet weld of high-strength steels were investigated. The S-N curve was fitted, and the corresponding fatigue life was predicted. Results corroborate that the base material of high-strength steel possess high fatigue resistance. AISC360 and EC3 standard design curves are applicable for the evaluation of the butt weld fatigue performance of Q460D and possess adequate safety margin, but only suitable for low-fatigue life estimation of Q690D butt weld. With respect to cross fillet weld, AISC360 design curve not only is suitable for the fatigue life analysis of Q460D and Q690D but also has enough safety margins, while EC3 and BS7608 codes possess relatively low fatigue limit. In addition, a quantitative analysis on fatigue fracture was conducted on the basis of fatigue damage theory, and the fatigue crack propagation law was disclosed on the basis of fracture morphology. The crack propagation law before instant fracture is consistent with damage development, and the fatigue striation width increases gradually with damage development. The fast crack propagation stage accounts for a small proportion in the fatigue life, thereby indicating that this stage is insufficiently developed.