Patent US3593025A successfully refreshed from Google Patents.
US3593025A
Expired / Lapsed
US
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Detecting defects by distribution of positron lifetimes in crystalline materials
Assignee: Midwest Research Institute
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Filing: 1968-06-14
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Granted: 1971-07-13
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Expires: 1988-06-14
Abstract
Abstract A method of nondestructively testing a structural member of crystalline material employs positrons from a radioactive source as a probe to detect the presence of latent defects in the crystalline structure of the member, such as those due to early fatigue damage or microscopic porosity. The half-life of positrons is longer in materials containing such defects than in undamaged materials; therefore, a measurement of the time of existence of positrons in a given material is effected and serves as an indication as to whether the half-life of the positrons in the material under test is longer than normal.
Inventors
- 👤 Joseph C Grosskreutz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:23
CPC Classifications
G; G01; G01N; G01N23/00; G01N23/20; G01N23/203; G01T; G01T1/00; G01T1/30
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
32 words
The method as claimed in claim 1, wherein is provided the additional step of: detecting any change from normal in said delay to thereby provide the indication that the member is defective.
Claim 2
Dependent Claim
51 words
The method as claimed in claim 1, wherein is provided the additional steps of: obtaining an indication of the half-life of positrons in said material at a second selected zone of said member; and detecting any difference in the half-lives of the positrons at the first-mentioned zone and the second zone.
Claim 3
Independent Claim
154 words
A method of nondestructively testing a structural member of crystalline material to determine the presence of latent defects in its crystalline structure, such as those due to early fatigue damage or microscopic porosity, said method comprising the steps of: providing a source of positron radiation; directing positrons from said source into said member at a selected zone thereof; sensing the timing of the application of said positrons to said zone; sensing the annihilation of the positrons introduced into the member at said zone; measuring the time interval between the time of application of each positron to said zone and the annihilation thereof to determine the lifetimes of the positrons introduced into the member at said zone; and detecting any change from normal in said measured time intervals indicative of a longer half-life than the normal half-life of positrons in the same material to indicate that the member is defective if said change is detected.
Claim 4
Dependent Claim
69 words
The method as claimed in claim 4, wherein said sensing of the annihilation of the positrons includes detecting the emission of characteristic energy produced when each positron is annihilated, and sensing the timing of said characteristic energy emissions, and wherein said time interval measuring is effected by measuring the delay between the time of application of each positron to said zone and the time of emission of said energy.
Claim 5
Dependent Claim
35 words
The method as claimed in claim 4, wherein said detecting of any change from normal in said time intervals includes counting the number of positrons annihilated at each of a plurality of said time intervals.
Claim 6
Dependent Claim
34 words
The method as claimed in claim 6, wherein said detecting of any change from normal in said time intervals further includes graphically displaying the distribution of the counts over said plurality of time intervals.
Claim 7
Dependent Claim
60 words
The method as claimed in claim 4, wherein said detecting of any change from normal in said time intervals includes determining the number of positrons annihilated at each of a plurality of said time intervals to thereby determine the distribution of the individual lifetimes of the positrons over a period extending from the shortest to the longest of said intervals.
Claim 8
Independent Claim
195 words
A system for nondestructively testing a structural member of crystalline material to determine whether latent defects such as those due to early fatigue damage or microscopic porosity are present in the crystalline structure of the member, said system comprising: a source of positron radiation for directing positrons into said member at a selected zone thereof; means for sensing the timing of the application of said positrons to said zone; means for sensing the annihilation of the positrons introduced into the member at said zone; means coupled with said application sensing means and said annihilation sensing means and responsive thereto for measuring the time interval between the time of application of each positron to Said zone and the annihilation thereof, whereby to determine the lifetimes of the positrons introduced into the member at said zone; and means coupled with said interval measuring means and responsive to time interval information therefrom for analyzing said information to provide an indication that the member is defective if the distribution of the individual lifetimes of the positrons is indicative of an increase in the half-life of the positrons as compared with the normal half-life of positrons in the same material.
Claim 9
Independent Claim
217 words
A system for nondestructively testing a structural member of crystalline material to determine whether latent defects such as those due to early fatigue damage or microscopic porosity are present in the crystalline structure of the member, said system comprising: a source of positron radiation for directing positrons into said member at a selected zone thereof; means for sensing the timing of the application of said positrons to said zone; means for sensing the annihilation of the positrons introduced into the member at said zone; time interval measuring means coupled with said application sensing means and said annihilation sensing means and responsive thereto for delivering output information indicative of the time interval between the time of application of each positron to said zone and the annihilation thereof, and thus indicative of the lifetimes of the positrons introduced into the member at said zone; and means coupled with said measuring means and receiving said output information therefrom for analyzing said information to determine the number of positrons annihilated at each of a plurality of said time intervals to provide an indication that the member is defective if the distribution of the individual lifetimes of the positrons is indicative of an increase in the half-life of the positrons as compared with the normal half-life of positrons in the same material.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-07-12 | 1975-01-11 | 1975-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-12 | 1979-01-11 | 1979-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-12 | 1983-01-11 | 1983-07-13 | $7700.00 | Window Closed / Lapsed |