Effect of different welding feature on the fatigue life of pipeline steel and flange welded joint

Objective The aim is study the influence of three welding features, full welding, incomplete welding and extended welding, on the fatigue life of pipeline steel and flange equivalent T-joints. Methods Three kinds of welding feature finite element models are established, and the accuracy of the simulation results is verified by a high frequency fatigue testing machine. Results The results show that the overall strain energy density change trend at the weld of the pipeline steel and flange equivalent T-joint is to decrease first, then gradually increase after reaching the peak valley. The minimum grid size is selected at the peak and valley positions, which is 5.5 mm.With the increase of the external stress, the number of fatigue gradually decreases, and the fracture position occurs at the position of the arc termination. The fatigue S-N curve of the test results and the simulation results is consistent. The maximum error is controlled within 13.3% at the stress of 60 kN. The use of simulation methods can effectively reduce the number of test samples and predict the number of fatigue cycles. Conclusion At the survival rate of 50% S-N curve and the fatigue strength of 2×10⁶ cycles, the fatigue strength of incomplete welding feature is 1.3% higher than that of the full welding feature, and 5.6% higher than that of the extended welding feature.The fatigue life of the incomplete welding feature is higher than that of the full welding feature and the extended welding feature.