US3887987A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making, and of measuring article fatigue life
Assignee: General Electric Co
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Filing: 1974-07-29
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Granted: 1975-06-10
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Expires: 1994-07-29
Abstract
Abstract Fatigue failure of an engineering article is primarily influenced by a natural inherent defect in the material from which the article is made. By an ability established to allocate a quantitative measure to such defect as a new material property influenced only by environment and material manufacturing procedures as are other basic properties, and using known methods for determining critical stress areas, a wide range of fatigue design data can be generated from a few basic measurements. Thus, from the deduction of a characteristic material defect length, there can be determined both a material''s basic fatigue properties and the fatigue capability of the article for which the material is used. Using the fatigue properties and fatigue capability so determined as a guide the article is either made to the original design or made to a reshaped design.
Inventors
- 👤 Trevor L Salt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 10:15
CPC Classifications
F; F01; F01D; F01D5/00; F01D5/30; F01D5/3007; G; G01; G01B; G01B7/00; G01B7/16; G01N; G01N17/00; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49764; Y10T29/49771
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
207 words
A method for making an article having at least a minimum selected useful fatigue life under certain operating conditions, the article being made of a selected material, comprising the steps of: making an initial design for the article; selecting from the design an area of relatively high stress; obtaining stress/strain data for the selected material; obtaining stress intensity/crack growth data and at least one fatigue characteristic for the selected material; determining a characteristic material defect length ( lambda ) for the selected material by: a. selecting at random a first characteristic material defect length for the selected material; and then b. comparing and modifying the length of the initial characteristic material defect length with the stress/strain data and stress intensity/crack growth data in an literative method until a characteristic material defect length ( lambda ) matches the fatigue characteristic; applying ( lambda ) to the stress data to determine the useful fatigue life of the article in the relatively high stress area, and then making the article to the design if the useful fatigue life is at least the selected minimum or reshaping the design of the relatively high stress area until the useful fatigue life is attained and then making the article to the reshaped design.
Claim 2
Independent Claim
207 words
A method for making an article having at least a minimum selected useful fatigue life under certain operating conditions, the article being made of a selected material, comprising the steps of: making an initial design for the article; selecting from the design an area of relatively high stress; obtaining stress/strain data for the selected material; obtaining stress intensity/crack growth data and at least one fatigue characteristic for the selected material; determining a characteristic material defect length ( lambda ) for the selected material by: a. selecting at random a first characteristic material defect length for the selected material; and then b. comparing and modifying the length of the initial characteristic material defect length with the stress/strain data and stress intensity/crack growth data in an literative method until a characteristic material defect length ( lambda ) matches the fatigue characteristic; applying ( lambda ) to the stress data to determine the useful fatigue life of the article in the relatively high stress area, and then making the article to the design if the useful fatigue life is at least the selected minimum or reshaping the design of the relatively high stress area until the useful fatigue life is attained and then making the article to the reshaped design.
Claim 3
Dependent Claim
197 words
The method of claim 1 in which the determination of the characteristic material defect length ( lambda ) comprises the steps of: obtaining for the selected material a stress/strain relationship from observed discrete points; constructing from known material test data the equivalent theoretical stress/strain relationship for cycling between two limits of items selected from the group of items consisting of stress and strain, the relationship having an equivalent linear relationship; obtaining for the selected material an observed relationship between stress intensity (SI) and crack growth per cycle (da/dN); obtaining as the fatigue characteristic an observed failure data point for the selected material at a first selected stess; and then determining the effective length ( lambda ) of the characteristic material defect by: a. selecting at random a first characteristic defect length, b. using the equivalent linear relationship for the theoretical stress/strain relationship and the observed relationship between SI and da/dN to determine if the first selected defect length fits the data for the observed failure data point for the selected fatigue property; and c. repeating the determination if no fit occurs by selecting substitute defect lengths until a desired fit occurs with the observed failure data point.
Claim 4
Dependent Claim
30 words
The method of claim 2 in which the material is tested to obtain data for yield strength, ultimate strength, reduction in area and Young''s modulus to obtain the stress/strain relationship.
Claim 5
Dependent Claim
88 words
The method of claim 2 in which the relationship between SI and da/dN is constructed using a lower value of stress intensity (KL) as an initial point, using an upper value of limiting critical stress intensity (KU) as a final point, and then constructing the relationship as a series of three connected substantially straight lines, the first of which starts at KL, the last of which terminates at KU and the intermediate of which has a constant slope relating to a common fourth power observation of crack propagation.
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) | 1978-06-09 | 1978-12-09 | 1979-06-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-09 | 1982-12-09 | 1983-06-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-09 | 1986-12-09 | 1987-06-10 | $7700.00 | Window Closed / Lapsed |