3D FEM Simulation of Velocity Effects on Magnetic Flux Leakage Testing Signals

摘要

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, 3D transient finite element model based on T-Ω formulation was used to analyze MFL system at high speed, with regard to eddy currents induced in steel tube because of the relative movement between the exciters and specimen. The eddy currents change the profile of electromagnetic field, which increase difficulty in MFL signals interpretation and defect identification. Typical 3D defects were modeled and MFL signals caused by the defects of different size were simulated respectively. Eddy current induced by velocity and their characterization in high speed MFL testing system were investigated. The MFL signals variations due to moving velocity of steel tube were examined and the relations between them were discussed as well.