Dual-frequency Eddy Current Non-destructive Detection of Fatigue Cracks in Compressor Discs of Aero Engines

Eddy current non-destructive testing is used to inspect the critical aircraft components. The shortcomings of the inspection method identified, based on a few accidents, necessitatethe development of high sensitive and reliable testing procedures for inspecting the critical safety related aircraft components. This paper discusses a dual-frequency eddy current testingprocedure developed for inspection of compressor discs of aero engines for detecting fatigue cracks with high sensitivity and reliability. This procedure is capable of detecting fatigue crackssmaller than 2 mm in comparison to 4 mm cracks that can be detected with the currently practiced eddy current testing procedure

A new approach for restoration of eddy current images

Eddy current images of defects are blurred due to convolution of point spread function of eddy current probe with defects. Disturbing variables such as lift-off, surface roughness, and material property variations influence the eddy current images. In order to restore the length, width, depth, and orientation of surface-breaking defects in the presence of disturbing variables, a new and comprehensive approach has been developed. This approach uses artificial neural network and image processing methods. Studies on austenitic steel plates confirm that through this approach it is possible to restore the spatial information of surface-breaking defects of uniform or slowly varying depth and also to form their accurate three-dimensional pictures. This approach is fast as well as amenable for automation