Development of a System to Invert Eddy-Current Data and Reconstruct Flaws

Publisher Website
Google Scholar
Abstract
Starting from rigorous electromagnetic theory, a model for the inversion of eddy-current data to reconstruct flaws in circular cylindrical tubes is developed. The form of the model consists of integral equations, whose kernels (Green's functions) are computed using Fourier transforms. The unknowns in the principal integral equation are the conductivity and electric field in the flawed region. Because these unknowns appear multiplied together, the problem is really nonlinear. The integral equations are converted to algebraic (vector-matrix) form by means of the method of moments. The inversion process is completed by applying linear and nonlinear least-squares algorithms, that are contained in the commercially available LINPACK/MINPACK software packages, to these algebraic equations. Using these algorithms in the model, we have reconstructed numerically-generated flaws with great accuracy, both when the flaws are 'deterministic' and 'random', the latter with data that has been perturbed by as much as 20%. Examples of these inversions, using both the linear and nonlinear algorithms, are presented. In addition, the model can be extended in a straightforward way to include the effects of known irregularities, such as tube supports or tube-flaring, on the reconstruction of flaws.

This publication has 0 references indexed in Scilit: