Abstract
In order to characterize the dynamic process of the crack growth in the weld of oil and gas pipelines, a mathematical model of fluid-solid-magnetic multifield coupling was constructed in this paper. Based on this model, the bidirectional fluid-solid coupling and unidirectional magnetic structure coupling caused by the weld deformation were achieved by dynamic application of the fluid permeation pressure, calculating the internal crack growth in the pipe weld, reconstructing the computational grid near the internal crack, and discussing the characteristics of the magnetic leakage field in the process of the internal crack growth in pipe weld. Thus, a fluid-solid-magnetic coupling algorithm for the internal crack growth in pipe welds considering fluid permeation pressure is established. According to the characteristics of the internal crack opening distance, internal crack growth length, crack tip energy release rate, peak values of magnetic induction intensity level, and vertical component, the process of the internal crack growth is measured. The results show that the fluid osmotic pressure accelerates the process of the internal crack growth and this algorithm can solve the problem of the characterization and evaluation of crack growth in pipe welds under fluid-solid-magnetic coupling action.
Highlights
Oil and gas pipelines are important ties to connect the production, transportation, and marketing as the transportation tool of petroleum and natural gas
The preliminary experimental research on different degrees and positions of typical cracking defect in the weld of oil and gas pipelines was carried out, and the magnetic induction intensity distribution in the leakage magnetic field caused by the pipe weld cracks was obtained, and the surface remanufacturing was studied [7, 8]
With the internal crack growth on inner wall of pipelines, the fluid penetrated into cracks and fluid osmotic pressure was generated, resulting in the acceleration of the internal crack propagation and the deformation of the pipeline weld structure
Summary
Oil and gas pipelines are important ties to connect the production, transportation, and marketing as the transportation tool of petroleum and natural gas. During MFL detection, such defect expansion is caused by fluid-structure interaction between the defect-space contact surface in inner wall of the weld and the transporting fluid, and this is accompanied with multifield coupling problem of magnetic force fields. The preliminary experimental research on different degrees and positions of typical cracking defect in the weld of oil and gas pipelines was carried out, and the magnetic induction intensity distribution in the leakage magnetic field caused by the pipe weld cracks was obtained, and the surface remanufacturing was studied [7, 8]. A simulation algorithm of the internal crack growth in the weld of oil and gas pipelines based on the fluid-solid-magnetic multifield coupling was established in this paper. The realization of the algorithm can provide a theoretical basis for the detection and evaluation of weld cracks in-service pipeline by using MFL method and the remanufacture, repair, or replacement of oil and gas pipelines
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