US4286216A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ferromagnetic resonance probe and method for flaw testing in metals
Assignee: Leland Stanford Junior University
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Filing: 1978-11-15
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Granted: 1981-08-25
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Expires: 1998-11-15
Abstract
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.
Inventors
- 👤 Bertram A. Auld
- 👤 Gary W. Elston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:30
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N22/00; G01N22/02; G01R; G01R33/00; G01R33/20; G01R33/24
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
76 words
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 DC , to said resonator, means for applying an rf magnetic field h 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.
Claim 2
Dependent Claim
76 words
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 DC , to said resonator, means for applying an rf magnetic field h 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.
Claim 3
Dependent Claim
21 words
A probe as in claim 1 in which the d.c. field H DC is applied parallel to the surface under test.
Claim 4
Dependent Claim
21 words
A probe as in claim 1 in which the d.c. field H DC is applied perpendicular to the surface under test.
Claim 5
Dependent Claim
37 words
A probe as in claim 1 in which the means for detecting changes in the resonant frequency includes means for varying the frequency of the rf magnetic field and determining the frequency at which the resonator resonates.
Claim 6
Dependent Claim
20 words
A probe as in claim 1 in which means is provided for varying the strength of the d.c. magnetic field.
Claim 7
Independent Claim
94 words
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.
Claim 8
Independent Claim
94 words
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.
Claim 9
Dependent Claim
20 words
The method as in claim 6 wherein the d.c. magnetic field is applied with a component perpendicular to the surface.
Claim 10
Dependent Claim
16 words
The method as in claim 6 wherein the d.c. magnetic field is parallel to the surface.
Claim 11
Independent Claim
55 words
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.
Claim 12
Independent Claim
55 words
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.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-08-24 | 1985-02-23 | 1985-08-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-08-24 | 1989-02-23 | 1989-08-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-08-24 | 1993-02-23 | 1993-08-25 | $7700.00 | Window Closed / Lapsed |