MAIN S-N CURVE FITTING AND METALLOGRAPHIC STRUCTURE ANALYSIS OF WELDED JOINT OF ROTARY DRILLING RIG

Wenjun Qian, Haijin Wang, Haoran Du, Xunan Zhang, Chaoqin Liu, Jixin Wang, Adeshara Jatinkumar V

ABSTRACT : In order to realize the accurate fatigue life analysis of the weld seam of the mast of the rotary drilling rig, a reasonable size of the welded joint sample was prepared in this paper, and the fatigue performance test of the welded joint was carried out by using the fatigue testing machine. The fatigue data under different nominal stresses were obtained, and the nominal stress S-N curve was fitted. Using finite element analysis, the node force at the weld toe section is extracted, and the equivalent node force and node bending moment of the weld toe section are obtained. The structural stress and equivalent structural stress of the welded joint of the sample are calculated, and the equivalent structural stress S-N curve is obtained. The fatigue performance of the welded joint is analyzed by metallographic observation, which is prepared for the next calculation of the fatigue life of the mast.

Keywords : Welded joints, welding fatigue test, S-N curve, nominal stress, equivalent structural stress, metallographic structure