A Thickness Reduction Detection Method Based on Magnetic Permeability Perturbation Under DC Magnetization for Ferromagnetic Components

The assessment of internal thickness reduction of ferromagnetic components has always been a critical issue in engineering. However, traditional nondestructive testing (NDT) methods have some limitations with the increase of wall thickness. Based on the nonlinear magnetization characteristics of ferromagnetic materials, a relationship between the thickness reduction and active excitation of changes in magnetic permeability is established, and a new thickness reduction detection method based on magnetic permeability perturbation (MPP) is proposed. The mechanism of thickness reduction detection based on MPP is analyzed by a theoretical model and the feasibility is verified through a series of simulations and experiments. Experimental results show that the measurement results have good linearity, and a thinning loss of 6.25% of wall thickness can be well detected. In addition, the effects of magnetizing current and excitation frequency on the amplitude and linearity of the detection signal are discussed in detail. This method does not benefit from the liftoff effect nor is it limited by the skin effect, which has great practical value as a supplement to the evaluation of thickness reduction for ferromagnetic components.