The fundamental structure and the basic detection principle of the plate remote-field eddy current testing system were introduced. According to the distribution characteristics of the magnetic flux and the energy of the testing system, a novel concept related to the hollow area in the energy was proposed. Simulation techniques were used to obtain the distribution characteristics of the magnetic flux density in the direction which mainly influenced the output signal, in the plane where the detection coil was placed, and in the presence or otherwise of a fault in the conductor plate. In particular, the influence of flatbottom hole flaws of varying depths and radii on the magnetic flux density was analyzed. The analysis showed that the change in the magnetic flux density distribution was directly related to the shape of the fault. The test results for low-frequency remote-field signals for the plate were given with hole flaws appearing on the top or bottom of the plate. The test curves showed the different influences of the depth, radius, and location of the flaw on the detection signal for the tested material.

 

ferromagnetic conductor, plate remote-field eddy-current; , magnetic field distribution, fault detection