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US3665751A
Expired / Lapsed
US
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Low-cycle fatigue testing machine
Assignee: National Aeronautics and Space Administration
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Filing: 1970-08-04
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Granted: 1972-05-30
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Expires: 1990-08-04
Abstract
Abstract A low-cycle, fatigue tester which simulates cyclic thermal loading by the application of cyclic mechanical stresses and deformations. The specimen is heated to the critical (most conducive to failure) temperature of the structure under consideration, and then deformed cyclically by the two interconnected, opposing, convex jaws of a mandrel driven reciprocally by an oscillating ram. The cyclic wrapping of the specimen around the opposing jaws of the mandrel mechanically induces alternating compression and tension stresses in the surface of the specimen which simulate the thermal stresses that would be caused by a temperature gradient through the depth of the structure under consideration. The stress level is controlled by the radius of the mandrel. The frequency of the oscillation is representative of the frequency of the thermal cycle affecting the structure under consideration.
Inventors
- 👤 Christos Demogenes
- 👤 Connie E Richard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 08:53
CPC Classifications
G; G01; G01N; G01N3/00; G01N3/32; G01N2203/00; G01N2203/02; G01N2203/022; G01N2203/0222; G01N2203/0226
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
92 words
A fatigue testing device comprising: a heating chamber serving to maintain a temperature actually experienced by a structure to be tested and which is most conducive to fatigue failure of the structure; a specimen; means for mounting said specimen in said chamber so that said specimen, including its ends, may deform freely; mandrel means for deforming said specimen in a shape simulating cyclic thermal loading which normally occurs due to a cyclic change in temperature gradient across the structure to be tested; oscillating means for imparting reciprocal motion to said mandrel means.
Claim 2
Dependent Claim
92 words
A fatigue testing device comprising: a heating chamber serving to maintain a temperature actually experienced by a structure to be tested and which is most conducive to fatigue failure of the structure; a specimen; means for mounting said specimen in said chamber so that said specimen, including its ends, may deform freely; mandrel means for deforming said specimen in a shape simulating cyclic thermal loading which normally occurs due to a cyclic change in temperature gradient across the structure to be tested; oscillating means for imparting reciprocal motion to said mandrel means.
Claim 3
Dependent Claim
78 words
The fatigue testing device of claim 1 wherein the mandrel means is comprised of two interconnected, opposing jaws convexly shaped to correspond to the desired thermal loading of the specimen, the surface of said specimen conforming with the surface of said jaws at points of contact between said specimen and said jaws, the said jaws serving to deform the specimen as the actual structure would deform if it were free to deform when subjected to thermal loading alone.
Claim 4
Dependent Claim
37 words
The fatigue testing device of claim 2 wherein the means for mounting said specimen includes bearings restraining ends of said specimen and permitting the entire specimen to deform freely in response to movement of said mandrel means.
Claim 5
Independent Claim
64 words
A method of metal fatigue testing whereby the stresses associated with thermal loading are mechanically simulated comprising the steps of: providing a specimen; heating said specimen to maintain a constant specimen temperature; mounting said specimen so that said specimen, including its ends, may deform freely; and mechanically bending said specimen in a shape simulating thermal loading caused by a temperature gradient across the structure.
Claim 6
Independent Claim
64 words
A method of metal fatigue testing whereby the stresses associated with thermal loading are mechanically simulated comprising the steps of: providing a specimen; heating said specimen to maintain a constant specimen temperature; mounting said specimen so that said specimen, including its ends, may deform freely; and mechanically bending said specimen in a shape simulating thermal loading caused by a temperature gradient across the structure.
Claim 7
Dependent Claim
52 words
The method of claim 4 wherein the step of mechanically bending includes cyclically bending said specimen in two opposite directions, in simulation of repeated thermal loading in the plastic strain range, the frequency of said cyclic bending beinG representative of the frequency of cyclic heating of a specimen undergoing cyclic thermal loading.
Claim 8
Dependent Claim
33 words
The method of claim 4 wherein the constant specimen temperature is maintained at a value which is the most critical and the most conducive to fatigue failure of a structural member under consideration.
Claim 9
Dependent Claim
60 words
The method of claim 5 including the further step of sealing and pressurizing said specimen, whereby a loss of pressure in the specimen indicates failure of the specimen due to fatigue cracks and wherein the constant specimen temperature is maintained at a value which simulates the temperature most critical or most conducive to fatigue of a structural member under consideration.
Claim 10
Independent Claim
77 words
A method of metal fatigue testing wherein the stresses associated with thermal loading caused by a temperature gradient across a structure are simulated comprising the steps of: providing a specimen; sealing and pressurizing said specimen; heating said specimen to a constant temperature; mechanically bending said specimen in a shape simulating thermal loading caused by a temperature gradient across the structure, whereby a loss of pressure in the specimen indicates failure of the specimen due to fatigue cracks.
Claim 11
Independent Claim
77 words
A method of metal fatigue testing wherein the stresses associated with thermal loading caused by a temperature gradient across a structure are simulated comprising the steps of: providing a specimen; sealing and pressurizing said specimen; heating said specimen to a constant temperature; mechanically bending said specimen in a shape simulating thermal loading caused by a temperature gradient across the structure, whereby a loss of pressure in the specimen indicates failure of the specimen due to fatigue cracks.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-30 | 1975-11-29 | 1976-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-30 | 1979-11-29 | 1980-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-30 | 1983-11-29 | 1984-05-30 | $7700.00 | Window Closed / Lapsed |