Fast numerical techniques for electromagnetic nondestructive evaluation

Abstract

This work is focused on quantitative imaging of defects in conductive materials by means of eddy current testing (ECT). By quantitative imaging we mean imaging methods based on numerical models of the interaction between the probe and the defect(s). The imaging methods attempt to provide an image of the defect at variance of commercial instruments that generally detect the defect and may have limited capabilities of extracting its major sizes by means of calibration curves obtained in predefined conditions. In addition, numerical models of the probe–defect interaction play a relevant role for the computer-aided design of the probe.

The paper will present methods for the solution of both the forward and the inverse problems. The methods have been developed ad hoc for ECT and have been optimised for accuracy and speed in view of real-time applications.

Keywords:

• eddy current testing
• nondestructive evaluation
• inverse problems
• crack reconstruction
• numerical models

Acknowledgements

The experimental data relative to fatigue crack and to stress corrosion, have been kindly provided by Dr Noritaka Yusa of International Institute of Universality, Tokyo, Japan. The authors thank Professor F. Villone for many helpful discussions and Dr M. Morozov for the support provided. This work was supported in part by the Association EURATOM/ENEA/CREATE, Italy.