3D MFL of steel pipe computation based on nodal-edge element coupled method

Edge element is more suitable for calculating nonlinear magnetic problem containing iron material due to its degree of freedom tangentially continuous. The magnetic flux leakage (MFL) of defect in steel pipe is simulated by using three dimensional(3D) hybrid finite element method (FEM) which couples nodal and edge element in this paper. According to the actual characteristics of steel pipe tested, the parameters of coils are optimized in order to obtain the optimal signal-to-noise ratio. MFL results are respectively calculated for defects of various shapes and dimensions. A novel meshing method is proposed to achieve convergence solution in adjacent area of very tiny defects. The simulation results agree well with the experimental data. Such a research can be employed for identifying defects in steel pipe, which are inspected using the MFL method of nondestructive testing.