US3908447A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of measuring article fatigue life
Assignee: General Electric Co
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Filing: 1973-01-15
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Granted: 1975-09-30
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Expires: 1993-01-15
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 crticial 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.
Inventors
- 👤 Trevor L Salt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:19
CPC Classifications
G; G01; G01N; G01N3/00
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
161 words
A method for testing an article design intended to have at least a minimum selected useful fatigue life under certain operating conditions, the article intendEd to be made of a selected material, and the article design having an area of relatively high stress, comprising the steps of: 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 iterative 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.
Claim 2
Independent Claim
161 words
A method for testing an article design intended to have at least a minimum selected useful fatigue life under certain operating conditions, the article intendEd to be made of a selected material, and the article design having an area of relatively high stress, comprising the steps of: 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 iterative 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.
Claim 3
Dependent Claim
27 words
The method of claim 1 in which the selected material is selected from the group consisting of metals, metal alloys, metal composites, non-metallic composites and their combinations.
Claim 4
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 stress; 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 5
Dependent Claim
30 words
The method of claim 3 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 6
Dependent Claim
88 words
The method of claim 3 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)
US3744300A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |