Non-Iterative MUSIC-Type Algorithm for Eddy-Current Nondestructive Evaluation of Metal Plates

A non-iterative MUSIC-type imaging algorithm for time-harmonic eddy-current testing of a damaged conductive plate is considered. The method is based (i) on a first-order asymptotic formulation of the secondary magnetic field observed outside the plate and induced by volumetric defects within it, which is valid when those are small enough with respect to the skin-depth at the frequency of operation, and (ii) on the singular value decomposition of the multistatic response matrix that can be collected using an appropriate source and sensor array. Herein, the asymptotic field formulation is validated by comparing the results with those provided by means of the CIVA platform in a realistic case. Further, the singular value pattern and MUSIC images are investigated, for a small spherical void placed at different locations inside a plate. A Gaussian distributed noise is added to the asymptotic data during the initial investigation, to alleviate inverse crime at least in part (more complex arrangements of source/sensor arrays and defects will be considered with external data in a later stage). Yet, these preliminary results as exhibited indicate the potential of the method to locate small defects in conductive materials in a typical eddy-current testing configuration