Presenter Information

B A. Auld, Stanford University

Location

Ithaca, NY

Start Date

1978 12:00 AM

Description

A new approach to microwave eddy current testing for surface cracks in metals involves the use of ferromagnetic resonance in a small garnet crystal placed close to the surface to be tested. It is well known in this case that the induced eddy currents on the metal surface cause a strong displacement of the ferromagnetic resonance frequency. The presence of a crack on the surface produces, by disturbing the eddy current pattern, a perturbation of the resonant frequency as the garnet sample passes over it. Theoretical detectability criteria for the garnet probe are developed on the basis of a magnetic perturbation relation and compared with calculations of Rayleigh wave and plate wave backward scattering and intermode scattering at a half-penny surface crack. Some experimental results are also given.

Book Title

Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE

Chapter

5. New Techniques and Phenomena

Pages

108-111

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

New Methods of Detection and Characterization of Surface Flaws

Ithaca, NY

A new approach to microwave eddy current testing for surface cracks in metals involves the use of ferromagnetic resonance in a small garnet crystal placed close to the surface to be tested. It is well known in this case that the induced eddy currents on the metal surface cause a strong displacement of the ferromagnetic resonance frequency. The presence of a crack on the surface produces, by disturbing the eddy current pattern, a perturbation of the resonant frequency as the garnet sample passes over it. Theoretical detectability criteria for the garnet probe are developed on the basis of a magnetic perturbation relation and compared with calculations of Rayleigh wave and plate wave backward scattering and intermode scattering at a half-penny surface crack. Some experimental results are also given.