US3854325A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and means for determining fatigue damage and surface stress
Assignee: United States Department of the Air Force
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Filing: 1973-07-13
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Granted: 1974-12-17
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Expires: 1993-07-13
Abstract
Abstract The test specimen is mounted on a movable table, ultrasonic surface waves are caused to travel across the specimen by a transducer fed from a CW signal source, a laser beam is passed through a beam splitter, one portion being reflected onto a photo-detector measuring signal amplitude, an output signal is compared with the output of the CW signal and the CW signal shifted in phase by 90*, these outputs measure ultrasonic phase difference, at points along the specimen; the second portion of laser beam is reflected from a mirror attached to the specimen table and back to a screen where an interference pattern is formed as the table is moved, photo detectors sense the changes in interference pattern and determine specimen displacement.
Inventors
- 👤 F Coate
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:39
CPC Classifications
G; G01; G01H; G01H9/00; G01N; G01N29/00; G01N29/04; G01N29/041; G01N29/22; G01N29/24; G01N29/2418; G01N2291/00; G01N2291/04; G01N2291/042; G01N2291/0423
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
93 words
A method for determining early fatigue damage and surface stress in metals comprising the steps of: transmitting an ultrasonic wave across a surface to be examined; directing a beam of coherent radiation at a point on the said surface, through the ultrasonic wave; detecting the reflected coherent radiation; moving the surface in a known manner; measuring the change in amplitude of the reflected radiation, and comparing the phase relationship of the reflected radiation to the ultrasonic wave whereby variations in said amplitude and phase will be indicative of fatigue damage and surface stress.
Claim 2
Independent Claim
93 words
A method for determining early fatigue damage and surface stress in metals comprising the steps of: transmitting an ultrasonic wave across a surface to be examined; directing a beam of coherent radiation at a point on the said surface, through the ultrasonic wave; detecting the reflected coherent radiation; moving the surface in a known manner; measuring the change in amplitude of the reflected radiation, and comparing the phase relationship of the reflected radiation to the ultrasonic wave whereby variations in said amplitude and phase will be indicative of fatigue damage and surface stress.
Claim 3
Independent Claim
138 words
A system for detecting fatigue damage and surface stress in metals comprising: means for supporting a test specimen; means attached to the support means for measuring displacement of the test specimen in a plane; means for generating an ultrasonic wave; means connected to the generating means for transmitting the ultrasonic wave along a surface of the test specimen; a source of coherent radiation; means for transmitting said radiation from the source to the surface; means for measuring the radiation reflected from the surface of the test specimen; display means connected to said measuring means to indicate the amplitude of said reflected radiation; phase detecting means connected to said generating means and said measuring means to detect changes in phase of said ultrasonic wave and said reflected radiation, and display means for providing an indication of said phase changes.
Claim 4
Independent Claim
138 words
A system for detecting fatigue damage and surface stress in metals comprising: means for supporting a test specimen; means attached to the support means for measuring displacement of the test specimen in a plane; means for generating an ultrasonic wave; means connected to the generating means for transmitting the ultrasonic wave along a surface of the test specimen; a source of coherent radiation; means for transmitting said radiation from the source to the surface; means for measuring the radiation reflected from the surface of the test specimen; display means connected to said measuring means to indicate the amplitude of said reflected radiation; phase detecting means connected to said generating means and said measuring means to detect changes in phase of said ultrasonic wave and said reflected radiation, and display means for providing an indication of said phase changes.
Claim 5
Dependent Claim
24 words
A system for detecting fatigue damage and surface stress in metals according to claim 2 wherein the means to indicate amplitude is an oscilloscope.
Claim 6
Dependent Claim
27 words
A system for detecting fatigue damage and surface stress in metals according to claim 2 wherein the display means for indicating phase changes is a digital counter.
Claim 7
Dependent Claim
28 words
A system for detecting fatigue damage and surface stress in metals according to claim 2 wherein the means for transmitting the ultrasonic wave is a surface wave transducer.
References Cited (Backward Citations)
US3471238A
Cited
US3745812A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-16 | 1978-06-17 | 1978-12-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-16 | 1982-06-17 | 1982-12-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-16 | 1986-06-17 | 1986-12-17 | $7700.00 | Window Closed / Lapsed |