Numerical simulation methods for motion-induced eddy current testing signals based on Ar formulation and edge finite elements

In this paper, numerical methods for simulation of the motion-induced eddy current testing (MIECT) signals were developed based on the reduced magnetic vector potential formulation (Ar method) and the edge finite element. According to the principle of the MIECT problem, numerical methods with reference frame referring to the transducer or the inspection object were developed respectively to solve the eddy current and pickup magnetic field signals. In addition, a quasi-static numerical scheme was also adopted to simulate the MIECT problem for inspecting crack along the moving direction. Based on the proposed numerical schemes and the conventional Ar code, numerical programs of the 3 methods were developed and validated for simulating MIECT signals. Through comparing the numerical results and efficiencies of the three simulation schemes each other, the validity of the proposed methods and the corresponding numerical codes were theoretically verified at first. Then, a MIECT experimental system and a prototype probe were developed and the validity of the proposed numerical methods were further proved experimentally. It is found that the moving probe-fixed object method is the most efficient scheme for MIECT signal simulation among the three proposed numerical methods. The numerical methods and codes developed in this paper provide numerical tools for design and optimization of the MIECT probes and testing system used in inspection of rails or wheels system etc, as well as the quantitative defect evaluation based on the MIECT signals through model based inverse analyses.