Research on the detection mechanism of defect in ferromagnetic materials using eddy current thermography

Eddy current thermography, as a new nondestructive testing method is the combination of electromagnetic induction heating and infrared thermography technology. The finite element simulation model of eddy current thermography is established. The heating mechanism of defect in the ferromagnetic material is analyzed using eddy current excitation. The influence of the conductivity and magnetic-permeability of the ferromagnetic material on the temperature and the temperature distribution of the structure being inspected containing multi-defects defects are researched. The results show that the influence of magnetic-permeability plays a significant role in the stable phase of the response. When the conductivity is slight, the influence of its change on the response is significant. When there are multi-defects in the component, the “central accumulation” phenomenon occurs in the temperature distribution. All the above research findings lay a theoretical foundation for the application of eddy current thermography.