Calibration Methods for Eddy Current Measurement Systems

Improved Probe-Flaw Interaction Modeling, Inversion Processing, and Surface Roughness Clutter

“…Figures 11 and 12 are plots of actual and predicted flaw dimensions obtained by applying this procedure to the NBS data. 7 The same information is also tabulated in Fig. 9.…”

Semi-Elliptical Surface Flaw EC Interaction and Inversion: Theory

“…Substituting the gradient of ¢ for H , using Maxwell's equations, and simplifying with various vector identities reduces Eq. (1) to the form (2) where the primed and unprimed quantities have the same significance as in Eq. (1).…”

“…In 1984 the concept of the flaw profile (a plot of the magnitude and phase of ~Z along the length of the flaw) was introduced as a tool for inverting eddy current measurements taken on surface breaking flaws interrogated with a spatially nonuniform probe field [1,2]. Comparison of direct measurements of approximately rectangular EDM notches with theoretical calculations for rectangular flaws showed satisfactory agreement.…”

Semi-Elliptical Surface Flaw EC Interaction and Inversion: Experiment

“…Following the development of the basic analysis for nonuniform probe fields [1], the first comparison of measured eddy current signals with predictions of the theory was made in 1983 [2]. The following year brought development of a full inversion procedure for rectangular flaws [3], which was successfully demonstrated using flaw signals measured for a series of rectangular electrical-discharge machined (EDM) notches in aluminum [4]. This year, in a companion paper [5], the model for interaction of nonuniform probe fields with flaws has been extended to semi-elliptical flaws.…”