S-N curve analysis of ring welding based on structural stress method

In engineering, △F-N curves are used to predict the fatigue life of ring welding, which is time-consuming, laborious and not universal. To improve the above inadequacies, an S-N curve for evaluating the fatigue life of the ring welding specimen was proposed. The fatigue life was obtained by tensile shear fatigue test with different ring welding specimens. The finite element model of ring welding structure was established by shell elements, beam elements and rigid elements, and the stress of ring welding structure under tensile shear load was calculated according to structural stress method. The S-N curve equation for fatigue life assessment of ring welding was obtained by linear fitting of fatigue data using two-parameter logarithmic model with the stress range △σ_s of nugget as the ordinate and the test life N as the abscissa. The results show that the data points were mostly within 5 times of the dispersed zone of life, and the predicted life was close to the real test life, which provided a reference for the life prediction of ring welding structures.