US3777555A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cumulative fatigue life indicator
Assignee: United States Department of the Navy
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Filing: 1972-05-03
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Granted: 1973-12-11
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Expires: 1992-05-03
Abstract
Abstract The purpose of this invention is accumulation and display of information indicative of expended and remaining fatigue life of a test specimen or pressure vessel. Strain-gauge output signals are amplified by a dual channel conditioning circuit. The dual channel bipolar strain signals are then used to compute the alternating stress range absolute value on a continuous basis. Voltage signals proportional to the alternating stress are then presented to a counter which registers the individual accumulated stress cycles with reference to the total allowable cycles in thousandths of counts and provides a usage factor indicating cumulative fatigue damage and remaining fatigue life.
Inventors
- 👤 E Petrisko
- 👤 K Keller
- 👤 P Keller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 04:51
CPC Classifications
G; G01; G01N; G01N3/00; G01N3/02; G01N3/06; G01N3/066; G01N2203/00; G01N2203/0058; G01N2203/0069; G01N2203/0073
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
164 words
A system for storing and indicating cumulative fatigue life of a structure comprising: a structure to be measured for cumulative fatigUe; strain gauge means attached to the structure along the principal stress axes for sensing cyclical strain; means connected to said strain gauge means and responsive thereto for generating alternating stress signals ES1 and ES2 wherein: ES1 K1 (Emax-Emin) ES2 K2(Emax + sigma Emin); and where, K1 is the modulus of elasticity of the material divided by 2(1+ sigma ); K2 is the modulus of elasticity of the material divided by 2(1sigma 2); Emax is the strain signal produced in response to strain in the direction of the maximum stress on the structure; Emin is the strain signal produced in response to strain in the direction of the minimum stress on the structure; sigma is the Poisson''s ratio; and further including: means connected to receive said cyclical stress signals, and responsive thereto for indicating the number of stress cycles at discrete levels of strain.
Claim 2
Independent Claim
164 words
A system for storing and indicating cumulative fatigue life of a structure comprising: a structure to be measured for cumulative fatigUe; strain gauge means attached to the structure along the principal stress axes for sensing cyclical strain; means connected to said strain gauge means and responsive thereto for generating alternating stress signals ES1 and ES2 wherein: ES1 K1 (Emax-Emin) ES2 K2(Emax + sigma Emin); and where, K1 is the modulus of elasticity of the material divided by 2(1+ sigma ); K2 is the modulus of elasticity of the material divided by 2(1sigma 2); Emax is the strain signal produced in response to strain in the direction of the maximum stress on the structure; Emin is the strain signal produced in response to strain in the direction of the minimum stress on the structure; sigma is the Poisson''s ratio; and further including: means connected to receive said cyclical stress signals, and responsive thereto for indicating the number of stress cycles at discrete levels of strain.
Claim 3
Dependent Claim
66 words
The system of claim 1 wherein: said means for indicating the number of accumulated stress cycles includes means for discriminating between ES1 and ES2 and selecting the larger of ES1 and ES2; and said means for indicating includes means responsive to said larger signal for storing and indicating the total cumulative stress cycles at each discrete level of stress corresponding to each discrete stress signal generated.
Claim 4
Dependent Claim
131 words
The system of claim 2 wherein: said means for storing and indicating the total cumulative stress cycles at each discrete level includes; means to generate a plurality of pulses corresponding to the larger of the signals ES1 or ES2; a first plurality of counters, each counter of said first plurality of counters corresponding to a respective discrete signal stress level; means responsive to said pulses for connecting said pulse generating means to a respective counter of said first plurality of counters corresponding to the signal stress level ES1 or ES2; said respective counter being incremented in response to a pulse generated by said pulse generator; said incrementing pulse being generated in response to said stress signal ES1 or ES2 dropping below a predetermined threshold at the end of each strain cycle.
Claim 5
Dependent Claim
44 words
The system of claim 3 wherein: said counters are each calibrated to generate a single output pulse in response to x pulses received where x is equal to one one-thousandths of the allowable stress cycles at the stress level corresponding to said respective counters.
Claim 6
Dependent Claim
119 words
The system of claim 4 including: a second plurality of counters; wherein: each said counter of said first plurality of counters connected to said pulse generator responsive to a stress signal ES1 or ES2 has its output connected to a corresponding counter of said second plurality of counters and incrementing said corresponding counter of said second plurality of counters in response to receiving x increments from said pulse generator; and including: a usage counter; all said first plurality of counters being connected to said usage counter for indicating the cumulative usage factor; said counter for indicating cumulative usage factor being incremented for each pulse output for each of said first plurality of counters and indicating the cumulative fatigue damage.
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) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |