Patent DE550425C successfully refreshed from Google Patents.
Patent US3812709A successfully refreshed from Google Patents.
US3812709A
Expired / Lapsed
US
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Stress gage
Assignee: Thermo Fisher Scientific Inc
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Filing: 1972-02-09
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Granted: 1974-05-28
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Expires: 1992-02-09
Abstract
Abstract This application discloses a system for non-destructive measurement of stress in metallic specimens by use of elastic wave energy, preferably shear or surface waves in the ultrasonic frequency range. More particularly, there is described a measuring technique using either type of wave according to which the relative transit times for the ultrasonic waves over a fixed path length and along two principal axes of stress are determined with a precision equal substantially to one nanosecond. A selfcontained stress gage instrument for practising the procedure is disclosed.
Inventors
- 👤 R Benson
- 👤 J Chapman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 13:27
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/04; G01N29/07
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
293 words
In an electro-acoustic instrument for measuring stress in a specimen of metal by propagating elastic waves in the specimen and determining the relative transit times for such waves over similar path lengths of propagation along two principal axes of stress, the improvement comprising: an electronic oscillator arranged to run at a prescribed frequency, first means to gate said oscillator into oscillation to emit a first train of oscillations at said frequency enduring for a first period between a few and several microseconds long, electromechanical transducer means for applying elastic wave energy to said specimen and means to apply said train to said transducer means for initiating transit of said specimen by a corresponding train of elastic waves, electromechanical transducer means for receiving said train of elastic waves at completion of said transit and providing in response thereto A train of received electrical oscillations enduring for a time equal substantially to said first period, second means to gate said oscillator into oscillation to emit a second train of oscillations at said frequency for a second period shorter than said first period, each of said first and second gating means being arranged to gate said oscillator into oscillation in the same polarity-going direction, adjustable time delay means coupled between said first and second gating means for adjusting said second period in time with reference to said first period with a precision equal substantially to one nanosecond, and signal comparator means arranged to receive said received electrical oscillations and said second train of oscillations for comparison when simultaneously present therein, said time delay means being operable to present said second train of oscillations to said comparator means in a time interval that is adjustable within the time period when said received electrical oscillations are present therein.
Claim 2
Dependent Claim
293 words
In an electro-acoustic instrument for measuring stress in a specimen of metal by propagating elastic waves in the specimen and determining the relative transit times for such waves over similar path lengths of propagation along two principal axes of stress, the improvement comprising: an electronic oscillator arranged to run at a prescribed frequency, first means to gate said oscillator into oscillation to emit a first train of oscillations at said frequency enduring for a first period between a few and several microseconds long, electromechanical transducer means for applying elastic wave energy to said specimen and means to apply said train to said transducer means for initiating transit of said specimen by a corresponding train of elastic waves, electromechanical transducer means for receiving said train of elastic waves at completion of said transit and providing in response thereto A train of received electrical oscillations enduring for a time equal substantially to said first period, second means to gate said oscillator into oscillation to emit a second train of oscillations at said frequency for a second period shorter than said first period, each of said first and second gating means being arranged to gate said oscillator into oscillation in the same polarity-going direction, adjustable time delay means coupled between said first and second gating means for adjusting said second period in time with reference to said first period with a precision equal substantially to one nanosecond, and signal comparator means arranged to receive said received electrical oscillations and said second train of oscillations for comparison when simultaneously present therein, said time delay means being operable to present said second train of oscillations to said comparator means in a time interval that is adjustable within the time period when said received electrical oscillations are present therein.
Claim 3
Dependent Claim
59 words
An instrument according to claim 1 in which each of said first and second gating means includes respectively a first and a second triggerable monostable multivibrator each of which upon being triggered with a trigger voltage provides a single gating pulse of the same polarity, said gating pulses having time durations equal, respectively to said first and second periods.
Claim 4
Dependent Claim
31 words
An instrument according to claim 1 having a common source of trigger voltage connected directly to said first gating means and through said time delay means to said second gating means.
Claim 5
Dependent Claim
63 words
An instrument according to claim 1 in which said means to apply said first train of oscillations to said transducer means is a gated device which requires to be gated to an operative state, and a connection is provided between said first gating means and said gated device to render operative said applying means for at least the duration of said first period.
Claim 6
Dependent Claim
30 words
An instrument according to claim 4 in which a separate connection between said oscillator and said signal comparator means provides said second train of oscillations to said signal comparator means.
Claim 7
Dependent Claim
66 words
An instrument according to claim 2 in which said means to apply said first train of oscillations to said transducer means is a gated device which requires to be gated to an operative state, and a connection is provided between said first multivibrator to provide the gating pulse thereof to said gated device to render operative said applying means for the duration of said first period.
Claim 8
Dependent Claim
41 words
An instrument according to claim 1 in which said time delay means is operable to adjust said time interval with a precision such that said second train of oscillations is in phase opposition to said received electrical oscillations in said comparator.
Claim 9
Dependent Claim
45 words
An instrument according to claim 1 including means to alter said prescribed frequency for making a measurement on a given specimen of metal first at one prescribed frequency and thereafter at another, to determine a stress parameter as a function of change in said frequency.
Claim 10
Dependent Claim
51 words
An instrument according to claim 1 in which said transducer means comprise a first electromechanical transducer for location at a first position on said specimen, for initiating said transit, and a second separate electromechanical transducer for location at a second location on said specimen, for receiving said train of elastic waves.
Claim 11
Dependent Claim
22 words
An instrument according to claim 1 in which said transducer means comprise a single electromechanical transducer to initiate and receive said waves.
Claim 12
Dependent Claim
181 words
In an electro-acoustic process of measuring stress in a specimen of metal by propagating elastic waves in the specimen and determining the relative transit times for such waves over similar path lengths of propagation along two principal axes of stress, the improvement comprising the steps of launching transverse elastic waves into the specimen responsive to a first burst of electrical oscillations at a prescribed frequency starting in a given polarity-going direction and enduring for a first time interval, generating a reference burst of electrical oscillations of the same frequency starting in the same polarity-going direction and enduring for a second time interval shorter than the first interval; providing an adjustable time delay on the order of tens of microseconds to a precision of approximately 1 nanosecond between said first and second bursts, receiving said elastic waves after transit over said path length and generating therefrom an electrical oscillation corresponding to said first burst, and adjusting said time delay to bring said reference burst into time-coincidence with said received-wave generated burst within the time interval of a single cycle of said frequency.
Claim 13
Dependent Claim
181 words
In an electro-acoustic process of measuring stress in a specimen of metal by propagating elastic waves in the specimen and determining the relative transit times for such waves over similar path lengths of propagation along two principal axes of stress, the improvement comprising the steps of launching transverse elastic waves into the specimen responsive to a first burst of electrical oscillations at a prescribed frequency starting in a given polarity-going direction and enduring for a first time interval, generating a reference burst of electrical oscillations of the same frequency starting in the same polarity-going direction and enduring for a second time interval shorter than the first interval; providing an adjustable time delay on the order of tens of microseconds to a precision of approximately 1 nanosecond between said first and second bursts, receiving said elastic waves after transit over said path length and generating therefrom an electrical oscillation corresponding to said first burst, and adjusting said time delay to bring said reference burst into time-coincidence with said received-wave generated burst within the time interval of a single cycle of said frequency.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-27 | 1977-11-26 | 1978-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-27 | 1981-11-26 | 1982-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-27 | 1985-11-26 | 1986-05-28 | $7700.00 | Window Closed / Lapsed |