Ferromagnetic resonance probe and method for flaw testing in metals
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsBertram A. Auld, Gary W. Elston
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Abstract
A probe and method for detecting surface flaws in metals. The probe operates at microwave frequencies and uses a ferromagnetic resonator. The resonator experiences a frequency shift when brought into proximity with a metal because of the perturbations of the demagnetizing fields at the boundaries of the resonator. A crack in the metal additionally disturbs the field and causes additional perturbations of the frequency. The perturbations in frequency are detected to provide an indication of flaws in the surface of the metal.
Claims9
A probe for scanning a metal surface to test for flaws in the metal surface comprising a ferromagnetic resonator, means for applying a d.c. bias magnetic field, H.sub.DC, to said resonator, means for applying an rf magnetic field h.sub.rf to said resonator orthogonally to said d.c. magnetic field, and means coupled to said resonator for detecting changes in the resonant frequency of said resonator responsive to flaws in the metal surface under test.
The method of detecting flaws in a metal surface which comprises the steps of disposing a ferromagnetic resonator adjacent the surface and scanning the surface, applying a d.c. magnetic field to said resonator, applying an rf magnetic field to said resonator, sweeping the frequency of the rf magnetic field so that it causes the resonator to resonate, determining the resonant frequency or impedance of said resonator when it is adjacent to the flawless surface and detecting changes in the resonant frequency or impedance as the resonator is disposed adjacent a flaw in the surface.
The method of detecting flaws in a metal surface which comprises the steps of disposing a ferromagnetic resonator adjacent said metal surface, exciting said resonator so that it resonates at a frequency which is determined in part by the metal surface, and detecting changes in the resonant frequency induced by flaws in the metal surface.
Dependencies are inferred from the claim text.