Aging Theories for Establishing Safe Life Spans of Airborne Critical Structural Components
Ko, William L. (2003) Aging Theories for Establishing Safe Life Spans of Airborne Critical Structural Components. Technical Report NASA/TP-2003-212034, Research Engineering, NASA Dryden Flight Research Center.
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Abstract
New aging theories have been developed to establish the safe life span of airborne critical structural components such as B-52B aircraft pylon hooks for carrying air-launch drop-test vehicles. The new aging theories use the “equivalent-constant-amplitude loading spectrum” to represent the actual random loading spectrum with the same damaging effect. The crack growth due to random loading cycling of the first flight is calculated using the half-cycle theory, and then extrapolated to all the crack growths of the subsequent flights. The predictions of the new aging theories (finite difference aging theory and closed-form aging theory) are compared with the classical flight-test life theory and the previously developed Ko first- and Ko second-order aging theories. The new aging theories predict the number of safe flights as considerably lower than that predicted by the classical aging theory, and slightly lower than those predicted by the Ko first- and Ko second-order aging theories due to the inclusion of all the higher order terms.
| EPrint Type: | NASA Technical Publication |
|---|---|
| Keywords: | Closed-form aging theory, Discrete aging theory, Equivalent constant stress cycle, Half cycle theory, Number of safe flights, B-52B aircraft |
| Subjects: | Aircraft/Project: B-52 (31 - 39) Engineering: (39) Structural Mechanics |
| ID Code: | 13 |
| Deposited On: | 28 May 2004 |
| Additional Information: | 40 pages. Errata on page 14, table 2, column C. |
