US3793874A
Expired / Lapsed
US
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Method for determining fracture toughness using small specimens
Assignee: SRI International Inc
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Filing: 1972-08-25
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Granted: 1974-02-26
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Expires: 1992-08-25
Abstract
Abstract A method for determining the plane strain fracture toughness KIc of a material. A specimen of a material is impacted with a gas gun to produce flat plate impact and hence uniaxial strain. The specimen is recovered, sectioned and the size distribution of internal cracks determined. The specimen is then impacted again, sectioned, and the new crack size distribution determined. The old and new crack distributions are then compared to determine ac, the critical crack half length of radius above which cracks grew and below which they did not. Knowing the tensile stress caused by the second impact and the critical crack half length, the fracture toughness is then calculated from the appropriate fracture mechanics expression.
Inventors
- 👤 D Shockey
- 👤 D Curran
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:12
CPC Classifications
G; G01; G01N; G01N3/00; G01N3/30; G01N3/307; G01N2203/00; G01N2203/0058; G01N2203/006; G01N2203/0062; G01N2203/0066; G01N2203/02; G01N2203/06; G01N2203/0617; G01N2203/0623
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
96 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a specimen of the material to produce uniaxial strain which causes internal cracks in the specimen, determining the size distribution of the internal cracks in the specimen, loading the specimen again, determining the new internal crack size distribution and comparing the new crack size distribution with the former crack size distribution whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 2
Independent Claim
96 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a specimen of the material to produce uniaxial strain which causes internal cracks in the specimen, determining the size distribution of the internal cracks in the specimen, loading the specimen again, determining the new internal crack size distribution and comparing the new crack size distribution with the former crack size distribution whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 3
Independent Claim
108 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a first specimen of the material to produce uniaxial strain which causes internal cracks in the specimen, determining the size distribution of the internal cracks in the specimen, preparing a second specimen from a portion of the first specimen, loading the second specimen, determining the new internal crack size distribution and comparing the new crack size distribution with the former crack size distribution whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 4
Independent Claim
108 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a first specimen of the material to produce uniaxial strain which causes internal cracks in the specimen, determining the size distribution of the internal cracks in the specimen, preparing a second specimen from a portion of the first specimen, loading the second specimen, determining the new internal crack size distribution and comparing the new crack size distribution with the former crack size distribution whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 5
Dependent Claim
25 words
A method in accordance with claim 2 wherein the specimens have a high aspect ratio and in which the loading is accomplished through flat-plate impacting.
Claim 6
Dependent Claim
22 words
A method in accordance with claim 2 including the step of sectioning the specimens after each impact to expose the internal cracks.
Claim 7
Dependent Claim
33 words
A method in accordance with claim 2 including the step of determining the stress sigma to which the second specimen is subjected during loading so that the fracture toughness KIc can be computed.
Claim 8
Dependent Claim
44 words
A method in accordance with claim 4 wherein the steps of determining the size distribution of internal cracks in the first and second specimens comprise determining the surface distribution of internal cracks and determining from the surface distribution the volume distribution of internal cracks.
Claim 9
Independent Claim
114 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a specimen of the material to produce uniaxial strain, said loading producing an initial tension phase in the specimen causing internal cracks to be propagated, said loading also producing a subsequent tensile reverberation which repropagates cracks produced during the initial tension phase, determining the size of the smallest crack propagated during the second tension phase, determining the size of the largest crack not propagated during the second tension phrase whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 10
Independent Claim
114 words
A method for determining the plane strain fracture toughness KIc of a material by determining the critical crack half length ac comprising the steps of loading a specimen of the material to produce uniaxial strain, said loading producing an initial tension phase in the specimen causing internal cracks to be propagated, said loading also producing a subsequent tensile reverberation which repropagates cracks produced during the initial tension phase, determining the size of the smallest crack propagated during the second tension phase, determining the size of the largest crack not propagated during the second tension phrase whereby the critical crack half length ac above which cracks grew and below which they did not is determined.
Claim 11
Dependent Claim
18 words
A method in accordance with claim 7 wherein the loading of the specimen is accomplished by flat-plate impacting.
Claim 12
Dependent Claim
21 words
A method in accordance with claim 7 including the step of determining the stress in the specimen during the tensile reverberation.
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) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |