Ferrite-yoke based pulsed induction thermography for cracks quantitative evaluation

This paper proposes a new ferrite-yoke based pulsed induction thermography (PIT) for cracks visualization and quantitative evaluation. The proposed approach combines the advantages of both alternating current field measurement (ACFM) and eddy current pulsed thermography (ECPT) in physical level. It can produce relative uniform heating in surface and subsurface of ferromagnetic material and have an open-view for infrared imaging. The structure and physical mechanism of the ferrite-yoke based PIT are introduced. Numerical simulations are conducted to understand the general behavior and multi-physical interactions of the proposed method with stimulated magnetic flux, eddy current and induced heating in samples. Experiments are implemented to verify simulation results and identify the characteristics of the proposed method for characterization of the artificial and natural cracks. Results demonstrate the advantages of the proposed method on cracks quantitative evaluation in terms of combined magnetic flux and eddy current heating to defect orientations, uniform inductive stimulation and open-view for cracks visualization. The proposed method greatly enhances the capability for cracks detection and quantitative evaluation compared with previous induction coils.