Research On Key Factors Of Crack Heating Model Under Alternating Magnetic Field

Non-destructive testing has been more important to improve the product quality. The traditional NDT methods have been difficult to meet the testing requirements, thus the non-destructive testing method based on infrared thermal imaging has become the emerging field. And the infrared thermal imaging defect detection method under alternating magnetic field is the current research focus. But the researches didn’t cover all the situations. The main research focuses on the method whose heat source is eddy current loss, and the application of detection is the main purpose. Nobody focused on the thermography detection method induced by hysteresis loss. The study did not take all possible detection situations into account. The detection concentrated on the vertical excitation, with little on parallel excitation. A few articles show that there is no response for non- ferromagnetic material under parallel excitation without eliminating the incentive inhomogeneity, and a temperature raise will show on the ferromagnetic material under parallel excitation but without sufficient experimental data supporting it.In this dissertation, According to the two types of hysteresis, eddy current loss, material simulation and experiments were carried out and the mechanism of heat was analyzed on conductive ferromagnetic materials, conductive non-ferromagnetic material and non-conductive ferromagnetic materials with the condition of alternating magnetic field as the excitation source, infrared camera as the temperature detection devices, based on the eddy current losses, hysteresis loss as the heat source. This dissertation provides theoretical guidance for the design of thermal imaging detection method, and lays the foundation for the quantitative analysis of defects. The main contents of this dissertation are as follows:(1) Temperature response and principle are analyzed under parallel vertical excitation in conductive ferromagnetic materials and conductive non-ferromagnetic material with COMSOL simulation software when eddy current loss is the main heat source.(2) The response is analyzed with COMSOL in Nonconductive ferromagnetic material under alternating magnetic field when hysteresis loss is the main heat source.(3) Experimental platform is built to verify the simulation results.