Crack Evaluation Based on Novel Circle-Ferrite Induction Thermography

Nondestructive inspection of rolling contact and stress corrosion cracks is a critical important research area in both science and technology industry to evaluate the properties of a product. This paper proposes a novel system of circle-ferrite pulsed inductive thermography for cracks inspection. The new sensing structure consists of several promising characteristics. It significantly enhances the detectability of omnidirectional micro cracks, and provides larger detection area with non-geometry influence. In addition, unlike common inductor, the proposed structure imposes uniform toroidal electromagnetic thermal fields, so that both sensitivities of detection rate and the detectable area can be simultaneously improved. This overcomes the problem of in-homogenous heating, and increases the thermal contrast between directional defective and non-defective region. The theoretical derivation based on magnetic circuit principles has been developed for analysis and interpretation of the results. In addition, both simulation experiments and tests on artificial and nature cracks sample have been conducted to show the reliability and efficiency of the proposed system.