The effect of the defect location on the finite element modelling of defect MFL fields

Magnetic flux leakage (MFL) measurement is one of the most widely used non-destructive testing techniques for in-service inspection of oil & gas pipelines. Numerical computation techniques, such as the finite element method (FEM), have been successfully employed for the study of flux leakage fields. FEM has special advantages when predicting the field profiles of simulated corrosion defects because it can model complex boundary geometries and non-linear material characteristics. According to the traditional FEM modelling method, the defect should be placed at different locations along the pipe to simulate the movement of the MFL inspection tool inside the pipe. In this paper, the effect of defect location within the finite element model is discussed and a simplified FEM modelling method is introduced. The simulation results obtained from the new method are compared to those of the traditional method. It is found that the new method can significantly shorten the solution times without compromising the accuracy of the FEM model of MFL inspection.