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Time to Flutter of a Maneuvering Viscoelastic Goland Wing

机译:挥动粘弹性戈兰翼的时间

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摘要

The use of high polymer composite materials in aircraft requires the incorporation of viscoelastic effects during the design process to fully capture the capabilities of these materials. One design analysis of concern is the prediction of flutter for an aircraft wing because flutter may result in the catastrophic failure of the wing. The current analysis assumes that the wing material is elastic which neglects the time dependent memory effect that appears for viscoelastic materials such as polymer composites. Previous work has shown that the viscoelastic effects lead to a flutter time in addition to a flutter speed. This earlier time to flutter theory was limited to constant flight speeds during the analysis so the effects of past maneuvers and mission profiles could not be explored. An expanded theory using an operator mapping is possible and captures the effects of maneuvers. Further, the theory is implemented in Matlab to provide numerical examples using a viscoelastic Goland wing. The results show that the time to flutter for most scenarios is limited to twice the relaxation period of the material, and that the results are sensitive to the functions used to represent the changes in flight velocity. Time to flutter decreases with increasing flight cycles, suggesting a trend similar to the fatigue limit of metals. For the viscoelastic Goland wing considered, 50,000 flight cycles per relaxation period is the maximum limit before flutter occurs instantaneously for a range flight velocities and viscosities.
机译:在飞机上使用高聚物复合材料需要在设计过程中引入粘弹性效应,以充分捕捉这些材料的功能。一种令人关注的设计分析是对飞机机翼的颤动的预测,因为颤动可能会导致机翼的灾难性故障。当前的分析假设机翼材料是弹性的,而忽略了粘弹性材料(例如聚合物复合材料)出现的随时间变化的记忆效应。先前的工作表明,粘弹性效应除了会导致颤动速度外,还会导致颤动时间的增加。在分析过程中,较早的颤振理论仅限于恒定的飞行速度,因此无法探讨过去的操作和任务配置文件的影响。使用操作员映射的扩展理论是可能的,并且可以捕获操纵的效果。此外,该理论在Matlab中得以实现,以提供使用粘弹性Goland机翼的数值示例。结果表明,在大多数情况下,颤振时间被限制为材料弛豫时间的两倍,并且结果对表示飞行速度变化的函数很敏感。颤动时间随飞行周期的增加而减少,这表明趋势类似于金属的疲劳极限。对于所考虑的粘弹性戈兰特机翼,对于一定范围的飞行速度和粘度,每个驰豫周期的50,000个飞行周期是在瞬时发生颤动之前的最大限制。

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