| タイトル | Investigation of Cracks Found in Helicopter Longerons |
| 本文（外部サイト） | http://hdl.handle.net/2060/20100011385 |
| 著者（英） | Newman, John A.; Wallace, Terryl A.; Baughman, James M. |
| 著者所属（英） | NASA Langley Research Center |
| 発行日 | 2009-07-15 |
| 言語 | eng |
| 内容記述 | Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces. |
| NASA分類 | Nonmetallic Materials |
| レポートNO | LF99-9172 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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