Research on the Influence of Girth Weld Joint Matching Degree on the Safety Performance of High Steel Grade Pipeline Based on ASME Local Strain Limit Criterion

Abstract

In this study, numerical simulation is used to analyze the influence of the mechanical properties matching degree of weld, HAZ and base metal on the maximum axial strain of high steel grade pipeline. Based on ASME VIII-2 local strain limit criterion and cumulative damage model, the fracture process of girth weld structure under axial displacement and internal pressure is simulated with XFEM. The material parameters of base metal and weld which are necessary for the simulation calculation are obtained by monotonic tensile test, and the material parameters of HAZ are assumed to be lower than those of the weld and base metal to a certain extent. The results show that for different matching degree combinations, the crack initiation location always appears in the HAZ with the lowest mechanical properties, and the axial strain of the pipeline decreases with the increase of the internal pressure. For the undermatched girth weld, the lower the mechanical properties of the weld is, the smaller the maximum axial strain of the girth weld pipe is. For overmatched girth weld, when the internal pressure is less than 6 MPa, the maximum axial strain of 20% overmatched girth weld pipe is higher than that of 10% overmatched girth weld pipe. However, when the internal pressure is higher than 6 MPa, the maximum axial strain of 20% overmatched girth weld pipe is smaller.