Optimized Image Processing for Eddy Current‐Thermography

Eddy Current‐Thermography is a well known NDT‐technique for the detection of open and hidden cracks in metallic parts. Cracks disturb the induced eddy currents and generate therefore characteristic temperature profiles. These temperature profiles are visualized by a thermographic camera. But, there is a problem arising from the fact that the heat produced by the eddy current coil itself is very inhomogeneous. This inhomogeneous heat transfer masks the temperature of the crack especially when inspecting complex shaped parts. This masking can be removed effectively by using a Fourier transform algorithm focused on a specific region in the temperature — time behavior of the heated surface. The processed final images are of binary form and easy to evaluate automatically. Eddy Current‐Thermography and this image processing were optimized for some aero engine parts. The reliable and automated detection of cracks at these parts show the great potential of this technique.