直升机桨叶扬起下坠碰撞动响应计算

Computation of Dynamic Response for Helicopter Blade Droop Stop Impact

针对铰接式旋翼桨叶扬起下坠碰撞问题,采用中等变形梁模型,同时引入有限转角模拟桨叶绕铰的刚性运动。运用Hamilton原理建立桨叶扬起下坠碰撞动力学方程,采用隐式Newmark法计算桨叶在有初始挥舞角下的下坠碰撞响应。计算结果与试验数据的对比表明:如果采用定步长的方法计算响应,计算时间较长,计算结果会产生明显的延迟。为了解决上述问题,在碰撞前后设置了一碰撞缓冲区,采用了变步长的方法强制计算点在跳过此缓冲区时必须进入该区。此法在计算桨叶扬起下坠碰撞动响应时,能较好的解决计算延迟问题,计算时间大大减少,计算结果与试验数据吻合较好。

In order to investigate the dynamic characteristics of blade impact to droop stop, a moderate deflection beam model is adopted to deal with the elastic deformations, and the finite rotation is introduced to take account of the rigid motions around hinges. Dynamic equations of blade droop stop impact are derived by Hamilton principle. Implicit Newmark method is used to compute the dynamic response when blade is released with an initial flap hinge angle. Comparison of computation with test shows that the fixed step method results in time delay with test data and the computation time is much longer. To solve this problem, impact buffer area is inserted just before the impacting occurs. When jumping over this area, computation must go through this area by alterable steps. This method can solve the delay problem and computation time is reduced a lot. The results are in good agreement with the test data.