Micro crack detection near surface of ferromagnetic materials based on eddy current thermography

Eddy current thermography technique was adopted to detect micro cracks near surface of ferromagnetic materials. The method of parallel excitation and heat conduction was put forward to detect micro cracks near surface. The process of heating in cracks using eddy current thermography was simulated by numerical calculation. The temperature distribution around the crack and the influence on the detection results were analyzed. The parallel excitation was adopted for the detection test. The surface temperature distribution curve of the specimen was extracted, and the slope curve was got by differential. Finally, the detection and recognition on cracks were realized. The results show that the parallel excitation method of eddy current thermography can have an efficient detection on micro cracks near surface of ferromagnetic materials, and appropriate excitation time can contribute to the rise of the temperature contrast and the enhancement of the testing effect. All the above researches lay a foundation for the detection and quantitative identification of micro cracks near surface.