Automated compensation and classification algorithms for array probe eddy current nondestructive evaluation

Nondestructive evaluation (NDE) deals with the inspection of an object for determining its properties without destroying its usefulness. Applications include detection of cracking in steam generator tubing in nuclear power plants, aircrafts, etc. Eddy current NDE is one of the more commonly used techniques. This thesis focuses on the problem of multifrequency eddy current inspection of steam generator tubing. Specifically, the thesis examines the use of array probes in the steam generator inspection.; This thesis deals with the development of analysis algorithms for processing of eddy current data collected using array probes from steam generator tubes to detect various types of degradation. The thesis describes compensation algorithms for the effect of probe liftoff in array probe signals, and other signal processing techniques for enhancing the information content in the data. Lift-off compensation is achieved using various techniques including affine transformations and neural networks, which use both single and multi-frequency data. In addition, techniques including the continuous wavelet transform, mixing and classification algorithms are investigated to detect and classify degradation mechanisms. The algorithms developed as part of this thesis were validated on data generated using a numerical model, as well as data obtained by inspection of tubing from in-service steam generators. Results on these data sets indicate the ability of the algorithms for rapid and accurate analysis of array probe eddy current data.