High-cycle fatigue life assessment of welded cruciform joints of Q460D steel

Abstract

In this paper, a reliable high-cycle fatigue life assessment method based on unified crack growth approach is presented for welded cruciform joints. Considering the ellipsoidal fracture model of structural steel as the instability propagation (fracture) criterion of fatigue crack, this study investigates the failure mode of the welded cruciform joint of Q460D steel subjected to a high-cycle fatigue test. Following the ellipsoidal fracture model, a set of theoretical calculation and numerical simulation were established to investigate the fatigue cracking of the welded cruciform joints. The theoretical model was further proposed for estimating the fatigue life of the welded cruciform joints of Q460D steel using the unified crack growth approach. Based on the theoretical and simulated results, the unified crack growth approach and the allowable stress fatigue life formula recommended in China's current code “Standard for design of steel structures, GB50017-2017” were then evaluated and compared. The calculation errors of the unified crack growth approach and the fatigue life formula recommended in China's current code are −48.2% ∼ +8.3% and −60.2% ∼ −34.8%, respectively.