Patent US4064735A successfully refreshed from Google Patents.
US4064735A
Expired / Lapsed
US
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Excitation and spectral calibration of acoustic emission systems
Assignee: Department of National Defence
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Filing: 1976-07-21
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Granted: 1977-12-27
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Expires: 1996-07-21
Abstract
Abstract A method and apparatus for the excitation and spectral calibration of acoustic emission systems in which a helium or other gas jet is used as a calibration source which makes no mechanical contact with the specimen or structure under examination. The gas jet which simulates an acoustic emission event, is sprayed on a reference material which is acoustically coupled to either an acoustic emission transducer or to a transducer having a flat frequency response up to 1 MHz. The transducer spectra are measured in decibels and subtracted from each other thereby obtaining a "transducer calibration". The "calibrated" transducers are then coupled to a specimen under test, the gas jet is applied and a "gas jet system spectrum" is measured. The spectrum of acoustic emission activity is then measured and corrected by subtracting, in decibels, the "gas jet system spectrum", thereby obtaining system independent acoustic emission spectral information which can be used to compare results in other systems.
Inventors
- 👤 Thomas Sherret Hutchison
- 👤 Stuart Livingstone McBride
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:29
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/22; G01N29/30; G01H; G01H1/00; G01N29/14
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
134 words
A method for spectral calibration of acoustic emission systems, comprising a. acoustically coupling a first transducer, having a flat frequency response up to about 1 MHz, to a reference material; b. exciting said reference material with a broad spectrum noise means, thereby generating an output signal from said first transducer; c. measuring said output signal from said first transducer; d. acoustically coupling a second transducer to a test piece and exciting said test piece with said broad spectrum noise means, thereby generating an output signal from said second transducer; e. calibrating said output signal of said second transducer relative to said output signal of said first transducer; f. measuring an acoustic emission spectrum from said test piece; and g. correcting said acoustic emission spectrum relative to said calibrated output signal of said second transducer.
Claim 2
Independent Claim
134 words
A method for spectral calibration of acoustic emission systems, comprising a. acoustically coupling a first transducer, having a flat frequency response up to about 1 MHz, to a reference material; b. exciting said reference material with a broad spectrum noise means, thereby generating an output signal from said first transducer; c. measuring said output signal from said first transducer; d. acoustically coupling a second transducer to a test piece and exciting said test piece with said broad spectrum noise means, thereby generating an output signal from said second transducer; e. calibrating said output signal of said second transducer relative to said output signal of said first transducer; f. measuring an acoustic emission spectrum from said test piece; and g. correcting said acoustic emission spectrum relative to said calibrated output signal of said second transducer.
Claim 3
Dependent Claim
26 words
A method as claimed in claim 1 wherein said reference material and said test piece are excited by a gas jet applied to a surface thereof.
Claim 4
Dependent Claim
19 words
A method as claimed in claim 2 wherein said gas jet is a helium gas jet at 18-40 psi.
Claim 5
Dependent Claim
38 words
A method as claimed in claim 1, wherein said output signal of said first transducer, in decibels, is subtracted from the output signal of said second transducer, in decibels, thereby deriving a calibrated output of said second transducer.
Claim 6
Dependent Claim
28 words
A method as claimed in claim 4 wherein said calibrated output of said second transducer is subtracted from said acoustic emission spectrum thereby correcting said acoustic emission spectrum.
Claim 7
Dependent Claim
62 words
A method as claimed in claim 1 including the steps of: h. acoustically coupling said second transducer to said reference material and exciting said reference material with said broad spectrum noise means, thereby generating a second output signal from said second transducer; and i. calibrating said second output signal of said second transducer relative to the output signal of said first transducer.
Claim 8
Dependent Claim
27 words
A method as claimed in claim 6 wherein steps (h) and (i) are repeated for a plurality of transducers to thereby facilitate selection of a desired transducer.
Claim 9
Independent Claim
108 words
A method for calibrating a high frequency audio transducer comprising: a. acoustically coupling said transducer to a reference material and exciting said material with a broad spectrum noise means comprising a gas jet applied to a surface thereof, thereby generating an output signal from said transducer; b. amplifying and analysing said output signal; c. acoustically coupling a second transducer having a flat frequency response up to about 1 MHz to said reference material excited by said broad spectrum noise thereby generating a comparison output signal from said second transducer; d. amplifying and analysing said comparison output signal; and e. calibrating said output signal against said comparison output signal.
Claim 10
Independent Claim
108 words
A method for calibrating a high frequency audio transducer comprising: a. acoustically coupling said transducer to a reference material and exciting said material with a broad spectrum noise means comprising a gas jet applied to a surface thereof, thereby generating an output signal from said transducer; b. amplifying and analysing said output signal; c. acoustically coupling a second transducer having a flat frequency response up to about 1 MHz to said reference material excited by said broad spectrum noise thereby generating a comparison output signal from said second transducer; d. amplifying and analysing said comparison output signal; and e. calibrating said output signal against said comparison output signal.
Claim 11
Dependent Claim
20 words
A method as claimed in claim 8 wherein said gas jet is a helium gas jet applied at 18-40 psi.
Claim 12
Dependent Claim
108 words
Apparatus for use in spectral calibration of acoustic emission systems comprising: a reference material; a test piece; broad spectrum noise means for excitation of said reference material and said test piece; transducer means for acoustic coupling to said test piece; a comparison transducer having a flat frequency response up to about 1 MHz for acoustic coupling to said reference material; and means for recording and analysing an output signal from said transducer means coupled to said test piece relative to an output signal from said comparison transducer coupled to said reference material to produce a calibrated output signal representative of an acoustic emission event in said test piece.
Claim 13
Dependent Claim
108 words
Apparatus for use in spectral calibration of acoustic emission systems comprising: a reference material; a test piece; broad spectrum noise means for excitation of said reference material and said test piece; transducer means for acoustic coupling to said test piece; a comparison transducer having a flat frequency response up to about 1 MHz for acoustic coupling to said reference material; and means for recording and analysing an output signal from said transducer means coupled to said test piece relative to an output signal from said comparison transducer coupled to said reference material to produce a calibrated output signal representative of an acoustic emission event in said test piece.
Claim 14
Dependent Claim
14 words
Apparatus as claimed in claim 10 wherein said noise means is a gas jet.
Claim 15
Dependent Claim
15 words
Apparatus as claimed in claim 11 wherein said gas jet is a helium gas jet.
Claim 16
Dependent Claim
14 words
Apparatus as claimed in claim 10, wherein said reference material is an aluminum block.
Claim 17
Dependent Claim
24 words
Apparatus as claimed in claim 10, wherein said comparison transducer is an X-cut quartz crystal having a fundamental mechanical resonance at about 5 MHz.
Claim 18
Dependent Claim
23 words
Apparatus as claimed in claim 10, including means to amplify, filter and analyse output signals from said transducer means and said comparison transducer.
References Cited (Backward Citations)
US3830091A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-12-26 | 1981-06-27 | 1981-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-12-26 | 1985-06-27 | 1985-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-12-26 | 1989-06-27 | 1989-12-27 | $7700.00 | Window Closed / Lapsed |