US4364012A
Expired / Lapsed
US
⏱️ 0.0 years remaining
FMR Probe method utilizing main and spurious resonance modes for detecting surface flaws
Assignee: Leland Stanford Junior University
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Filing: 1980-03-03
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Granted: 1982-12-14
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Expires: 2000-03-03
Abstract
Abstract In ferromagnetic resonance (FMR) probe apparatus for detecting surface flaws in a metal surface, probe impedance changes resulting from flaws are distinguished from impedance changes resulting from probe lift-off from the metal surface. A constant magnitude dc magnetic field and a constant frequency and constant magnitude rf magnetic field are applied to the ferromagnetic crystal and the real and imaginary components of probe impedance are detected. The impedance changes due to flaws are at least partially orthogonal to the impedance changes due to lift-out, and by observing probe impedance on an oscilloscope the presence of a flow or the occurrence of lift-off are readily identified.
Inventors
- 👤 Bertram A. Auld
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:29
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9046; G01N27/9053; G01N22/00; G01N22/02
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
137 words
The method of detecting and distinguishing flaws in a metal surface detected by means of a ferromagnetic resonance probe from signals generated due to probe lift-off from the metal surface comprising the steps of: placing a ferromagnetic resonator adjacent to the surface, said resonator having a plurality of resonance modes, applying a dc magnetic field to said resonator, applying an rf magnetic field to said resonator, field coupling said probe and said surface with a main resonance mode and simultaneously at least one spurious mode of resonance, scanning said probe across said surface during said field coupling, and detecting during said scanning real and imaginary changes in impedance of said probe at a fixed frequency whereby probe impedance variation due to a flaw is generally orthogonal to probe impedance variation due to probe lift-off from said surface.
Claim 2
Independent Claim
137 words
The method of detecting and distinguishing flaws in a metal surface detected by means of a ferromagnetic resonance probe from signals generated due to probe lift-off from the metal surface comprising the steps of: placing a ferromagnetic resonator adjacent to the surface, said resonator having a plurality of resonance modes, applying a dc magnetic field to said resonator, applying an rf magnetic field to said resonator, field coupling said probe and said surface with a main resonance mode and simultaneously at least one spurious mode of resonance, scanning said probe across said surface during said field coupling, and detecting during said scanning real and imaginary changes in impedance of said probe at a fixed frequency whereby probe impedance variation due to a flaw is generally orthogonal to probe impedance variation due to probe lift-off from said surface.
Claim 3
Dependent Claim
35 words
The method of detecting flaws in a metal surface as defined by claim 1 wherein said step of detecting changes in impedance includes displaying real and imaginary components of impedance on a cathode ray tube.
Claim 4
Dependent Claim
50 words
The method of detecting flaws as defined by claim 1 or 2 wherein said step of applying a dc magnetic field includes maintaining the dc magnetic field constant in magnitude, and said step of applying an rf magnetic field includes maintaining said rf magnetic field constant in frequency and magnitude.
References Cited (Backward Citations)
US2799823A
Cited
US2832040A
Cited
US2948845A
Cited
US3085196A
Cited
US3159784A
Cited
US3302105A
Cited
US3576503A
Cited
US3931571A
Cited
US3909746A
Cited
US4155035A
Cited
US4048588A
Cited
JPS5543420A
Cited
US4290017A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-12-13 | 1986-06-14 | 1986-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-12-13 | 1990-06-14 | 1990-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-12-13 | 1994-06-14 | 1994-12-14 | $7700.00 | Window Closed / Lapsed |