剪切载荷下航空发动机螺栓松动行为及其临界值的数值模拟研究

Numerical Simulation of Bolt Loosening Behavior and Critical Value of Aeroengine under Shear Load

关键词:  剪切载荷  螺栓连接结构  松动行为  临界值  影响因素  数值模拟

Key words:  Shear load  Bolted structure  Loosening behavior  Critical value  Influencing factors  Numerical simulation

摘要:

为研究剪切载荷下螺栓连接结构松动行为，首先建立了多种螺栓连接结构精细有限元模型，进行了全六面体网格划分，并运用Yamamoto方法和Spowith方法验证了模型的有效性，然后通过多种模型仿真对比，分阶段首次研究了不同影响因素下塑性松动期、旋转松动期内以及整个松动期内的螺栓松动行为及其重要临界值。结果表明：剪切载荷下螺栓初始预紧应力和其材料屈服应力之比在1.32～1.44时，松动最不容易发生；存在一初始预紧力临界值，当初始预紧力小于此临界值时，松动开始于旋转松动期，反之经历整个松动期；存在两个剪切载荷幅值临界值，当大于第1临界值时，螺栓松动会发生反之不会发生，当大于第2临界值时，松动过程经历整个松动期，反之仅经历旋转松动期；剪切载荷幅值越大，螺栓松动越容易发生，松动变化速率不单调且在某一幅值处发生突变；一定区间内，存在一个螺纹啮合面间摩擦系数范围使得松动最难发生；偏心距离越大，松动越容易发生。

Abstract:

In order to study the loosening behavior of bolted structures under shear load， firstly， a variety of fine finite element models of bolted structures were established， the full hexahedral mesh was divided， and the effectiveness of the model was verified by Yamamoto method and Sopwith method. Then， through the simulation comparison of various models， the bolt loosening behavior and its important critical values in plastic loosening period， rotational loosening period and the whole loosening period under different influencing factors were studied for the first time. The results show that when the ratio of bolt initial pre-tightening stress to material yield stress under shear load is between 1.32 and 1.44， loosening is the least likely to occur. There is a critical value of initial preload. When the initial preload is less than this critical value， the loosening begins in the rotating loosening period， on the contrary， it goes through the whole loosening period. There are two critical values of shear load amplitude. When it is greater than the first critical value， bolt loosening will occur， otherwise it will not occur. When it is greater than the second critical value， the loosening process will experience the whole loosening period， on the contrary， it will only experience the rotating loosening period. The larger the shear load amplitude is， the easier the bolt loosening occurs， and the loosening change rate is not monotonous and sudden change occurs at a certain amplitude. In a certain range， there is a range of friction coefficient between thread mating surfaces which makes loosening the most difficult to occur. The larger the eccentric distance is， the easier it is to loosen.