Novel Yoke Structured Electromagnetic Thermography for Inspection of Natural Fatigue Cracks

Nondestructive detection of small fatigue cracks is a significative and challenging task in evaluating the properties of material. This paper proposes a novel yoke structured eddy current pulsed thermography (ECPT) system for micro fatigue cracks inspection on irregularly shaped metallic materials. The proposed detection model provides a region of interest with a relatively uniform magnetic field. The detectability and thermal contrast of omnidirectional micro fatigue cracks are enhanced remarkably. In addition, the configuration has advantages of dramatically increasing portability and efficiency for detecting complex workpiece since the detection is completely in the open view of the infrared camera. Finally, experimental studies have been conducted on natural fatigue cracks in order to validate the reliability and efficiency of the proposed sensing structure.