Automated NDT of railway wheels using induction thermography

Induction thermography is an active thermal testing technique based on generation of eddy currents in an electrically conducting material. The technique found successful applications for surface crack detection in various industrial branches, with the general aim of searching for alternatives to magnetic particle or liquid penetrant testing. Due to its fast and contactless operation this nondestructive thermographic testing technique shows a high potential for the fully automated testing of steel components. This contribution presents a prototype application of induction thermography in surface crack inspection of railway wheels. The flexibility of camera based solutions and the proven sensitivity of induction thermography to surface defects are the basis for a demonstrator for thermographic testing developed in Fraunhofer IZFP. In connection with the infrared camera and the inductor moved by a robot, fully automated testing of complex shapes is performed. A proper combination of signal and image processing algorithms allows automated and robust defect detection. The technique works generally without application of any surface treatment. Results of inspection of different railway wheels are presented.