#### Location

La Jolla, CA

#### Start Date

1-1-1983 12:00 AM

#### Description

We present a simple analytical method for predicting the eddy current signal (ΔZ) produced by a surface flaw of known dimensions, when interrogated by a probe with spatially varying magnetic field. The model is easily parameterized, and we use it to construct inversion schemes which can extract overall flaw dimensions from multiposition, multifrequency measurements. Our method is a type of Born approximation, in which we assume that the probe’s magnetic field at the mouth of the flaw can be used as a boundary condition on the electromagnetic field solutions inside the flaw. To simplify the calculation we have chosen a “rectangular” 3-dimensional flaw geometry for our model. We describe experimental measurements made with a new broadband probe on a variety of flaws. This probe operates in a frequency range of 200 kHz to 20 MHz and was designed to make the multifrequency measurements necessary for inversion purposes. Since inversion requires knowledge of the probe’s magnetic field shape, we describe experimental methods which determine the interrogating field geometry for any eddy current probe.

#### Book Title

Review of Progress in Quantitative Nondestructive Evaluation

#### Volume

2B

#### Chapter

Section 22: Inversion of Eddy Current Data

#### Pages

1501-1526

#### DOI

10.1007/978-1-4613-3706-5_101

#### Copyright Owner

Springer-Verlag US

#### Copyright Date

January 1983

#### Language

en

#### File Format

application/pdf

Inversion of Eddy Current Signals in a Nonuniform Probe Field

La Jolla, CA

We present a simple analytical method for predicting the eddy current signal (ΔZ) produced by a surface flaw of known dimensions, when interrogated by a probe with spatially varying magnetic field. The model is easily parameterized, and we use it to construct inversion schemes which can extract overall flaw dimensions from multiposition, multifrequency measurements. Our method is a type of Born approximation, in which we assume that the probe’s magnetic field at the mouth of the flaw can be used as a boundary condition on the electromagnetic field solutions inside the flaw. To simplify the calculation we have chosen a “rectangular” 3-dimensional flaw geometry for our model. We describe experimental measurements made with a new broadband probe on a variety of flaws. This probe operates in a frequency range of 200 kHz to 20 MHz and was designed to make the multifrequency measurements necessary for inversion purposes. Since inversion requires knowledge of the probe’s magnetic field shape, we describe experimental methods which determine the interrogating field geometry for any eddy current probe.