Non-destructive testing and evaluation utilizing frequency-domain EM modeling

This paper introduces an approach for electromagnetic non-destructive testing and evaluation. Starting with a formulation of an inverse scattering problem, the detection of a defect in a known host is achieved by the minimization of a suitable nonlinear function. The function relates the data measured from the structure under test to that predicted numerically using full-wave electromagnetic simulation at each optimization iteration. The problem is solved using a gradient-based optimizer. The approach features high computational efficiency despite the full-wave simulation. It employs adjoint-based techniques for the computation of the required sensitivity information. The approach is versatile as it allows the retrieval of geometrical as well as material-related parameters of the defect. The numerical examples concern defects in lossy media. The electromagnetic analysis is done with a frequency-domain solver based on the transmission line method.