Development of A 3-D Eddy Current Model for Nondestructive Testing Phenomena

Abstract

The success of two-dimensional eddy current models for modeling a variety of important nondestructive testing situations has been reported elsewhere1-3. These models, based on the finite element method, are limited to two-dimensional and axisymmetric geometries but, nevertheless are quite capable of providing important data for many practical test geometries which can be approximated by 2-D or axisymmetric formulations. The general NDT problem, is, however, a true three-dimensional problem and must be modeled as such. A 3-D eddy current model is, therefore, a natural and obvious extension of the 2-D modeling capabilities available today. Such a model is particularly valuable since the interaction between applied fields, induced currents and complicated material discontinuities cannot be described by closed form equations nor can they be approximated by 2-D geometries. In addition, such situations cannot be replicated experimentally and, therefore, the numerical model is in many cases the only practical way to provide training data for signal processing equipment and algorithms and indeed, the only way to determine defect characterization parameters to aid in the design of eddy current probes and testing equipment.