Abstract: A general fluid-solid-magnetic coupling method for single-crack and multi-cracks growth was provided by using virtual crack closure technique (VCCT) in this paper. The growth behavior of cracks in the pipe lines, which affected by the action of the fluid-pipe weld structure-magnetic coupling effect with the dynamic increase of the fluid pressure, was investigated in detail. Results indicate that when the pressure load of the relevant fluid increases every time, this method completes a crack increment growth, and it renews the crack geometry, then the mesh is reconstructed and the crack growth calculation and magnetic field analysis are carried out in this cycle, and the fluid-solid-magnetic coupling of weld crack growth in ferromagnetic pipeline is achieved. The numerical simulation examples of single-crack and multiple-cracks in different circumferential position of pipe weld are taken as numerical examples. The crack opening distance and crack growth length of crack growth are described according to the growth results. The peak value of horizontal component of magnetic induction intensity and the peak value of vertical component of magnetic induction intensity are applied to measure the dangerous grade of the location of cracks, so as to judge the damage position and damage degree of pipeline weld, and it is also used to identify multiple cracks or single cracks. The realization of the method can provide a theoretical basis for the detection and evaluation of weld cracks in in-service pipeline by magnetic flux leakage method, and the remanufacture, repair of pipelines.
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2018, Vol. 32 
