Location

Brunswick, ME

Start Date

1-1-1992 12:00 AM

Description

Eddy current nondestructive testing depends upon the interaction of time-varying electromagnetic fields with the material under test. The electromagnetic fields are applied to the material under test via some finite sized transducer, usually an inductive coil or set of coils. If the material is conducting the fields will penetrate the conductor, but will attenuate to negligible levels after some distance. The classical skin depth,δs=2/ωμσ−−−−−√=1/πfμσ−−−−−−√is the standard assumption for the characteristic distance of field penetration in conductors. This paper reports the results of a study which examined the decay of sinusoidal steady-state (AC) fields in conductors induced by finite sized coils. Comparisons are made among the classic Dodd and Deeds formulations [1], the 3D-axisymmetric finite element method (FEM) [2], and published results [3]. Where possible experimental observations were compared to the computed and published results.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

11A

Chapter

Chapter 1: Fundamentals of Standard Techniques

Section

Eddy Currents

Pages

299-306

DOI

10.1007/978-1-4615-3344-3_37

Language

en

File Format

application/pdf

Share

COinS
 
Jan 1st, 12:00 AM

Skin Depth Considerations in Eddy Current NDT

Brunswick, ME

Eddy current nondestructive testing depends upon the interaction of time-varying electromagnetic fields with the material under test. The electromagnetic fields are applied to the material under test via some finite sized transducer, usually an inductive coil or set of coils. If the material is conducting the fields will penetrate the conductor, but will attenuate to negligible levels after some distance. The classical skin depth,δs=2/ωμσ−−−−−√=1/πfμσ−−−−−−√is the standard assumption for the characteristic distance of field penetration in conductors. This paper reports the results of a study which examined the decay of sinusoidal steady-state (AC) fields in conductors induced by finite sized coils. Comparisons are made among the classic Dodd and Deeds formulations [1], the 3D-axisymmetric finite element method (FEM) [2], and published results [3]. Where possible experimental observations were compared to the computed and published results.