Fatigue experiment and assessment of Q420qFNH weathering steel in the unequal-thickness butt-welded joint.

The use of unequal-thickness butt-welded joints is widespread in bridge engineering, material savings mean a decrease in cost, which can lead to lower overall costs and significant benefits Because of their unique structures and propensity for stress concentration and weld defects, it is crucial to investigate their fatigue performance. In this study, 15 sets of unequal-thickness butt-welded joints based on Q420qFNH were subjected to fatigue tests. ABAQUS modelling and a stress-extraction process utilising distance iterations were employed in this study. The key findings demonstrated that the fatigue performance of these weathering steel butt joints was superior, and the stress variation at these joints exhibited greater complexity and resulted in a more pronounced multi-crack fusion effect. Additionally, an attempt was made to evaluate the fatigue behaviour of other welded joints and unequal-thickness butt-welded joints using the same approach as that presented herein. The fatigue evaluation method based on nominal stress yielded a significant scatter of 1:T s = 4.21. Iterations were conducted based on the scattering at various critical distances. The results indicate that based on the theory of critical distance, the scatter of 1:T s = 2.304 is lower than the scatter of 1:T s = 2.502 associated with the notch stress method. These findings suggest that employing this method for fatigue assessment yields favourable outcomes across diverse welded joints. • Fatigue tests of Q420qFNH weathering steel in the unequal-thickness butt-welded joint was carried out. • The fatigue failures of Q420qFNH weathering steel in the unequal-thickness butt-welded joint were investigated. • The theory of critical distance-based assessment method was adopted to estimate the fatigue resistance. [ABSTRACT FROM AUTHOR]