Study on fatigue behavior of butt-welded high-strength steel connections with surface cracks.

• Fatigue crack growth rates in base metal and heat-affected zone of butt-welded high-strength steels Q960, Q890, and HG785 were obtained. • Fatigue behavior of butt-welded high-strength steel connections with semielliptical surface cracks was studied experimentally. • An accurate theoretical method is proposed to predict the fatigue life and crack propagation trajectories of surface crack specimens. This paper presents a study on the fatigue behavior of butt-welded high-strength steels (HSSs) Q960, Q890, and HG785. Fatigue crack growth rate (FCGR) experiments in the base metal (BM) and heat-affected zone (HAZ) are conducted, and the fatigue parameters are fitted using the Paris Law. Scanning electron microscopy (SEM) is also performed. The results reveal that the FCGR in the HAZ is slower than that in the BM for HSS; Q960 exhibits the highest fatigue crack growth (FCG) resistance, followed by Q890 and HG785. Surface crack propagation experiments are conducted at a maximum stress of half yield strength and 200 MPa. At half yield strength, the fatigue life decreases as the stress range increases, while at 200 MPa, the fatigue life decreases as the steel yield strength decreases. Furthermore, it is found that the surface cracks initially grow faster in the depth direction and then shift to the through thickness crack along the width direction. Finally, a theoretical method for predicting the fatigue life and crack propagation trajectories of surface crack specimens is proposed based on the Paris Law to consider multidimensional crack propagation behavior. [ABSTRACT FROM AUTHOR]