3-d FEM simulation of velocity effects on magnetic flux leakage testing signals

The development of computer-based defect characterization scheme for magnetic flux leakage (MFL) method require adequate mathematical models to describe the complicated interactions of sources, fields, velocity and defects in materials. In this paper, a 3-D transient finite element model based on T-Omega formulation was used to analyse MFL system at high velocity, with regard to eddy currents induced in a steel tube because of the relative movement between the exciters and specimen. The eddy currents change the profile of electromagnetic field, which increases difficulty in MFL signals interpretation and defect identification. Typical 3-D defects were modeled and MFL signals caused by the defects of different sizes were simulated respectively. Eddy currents induced by velocity and their characterization in high velocity MFL testing system were investigated.