两种典型螺栓连接结构的刚度特性比较研究

针对法兰对接和径向套接两种典型舱段螺栓连接形式,基于有限元静刚度计算、动力学简化建模、冲击响应特性分析及结构冲击试验,系统研究了两种连接形式的轴向刚度特性及其对动力学冲击响应的影响.有限元静刚度分析揭示了法兰对接与径向套接的轴向拉压刚度分别是非对称的和对称的,而法兰对接的平均刚度更大.之后,为两种连接形式建立了统一的动力学模型,证明非对称的轴向拉压刚度导致结构在受到横向载荷作用时会产生附加的耦合轴向振动,并且利用高精度幂函数拟合刚度跳变,得到耦合轴向振动频率是弯曲振动频率的二倍的结论.最后,通过冲击动力学试验证明了法兰对接存在二倍频的耦合轴向振动,而径向套接则不存在该耦合振动.径向套接虽然一阶频率较低,但阻尼效果更好.

COMPARISON OF THE STIFFNESS CHARACTERISTICS OF TWO TYPICAL BOLTED JOINTS

A comprehensive comparison of the stiffness characteristics is made for the bolted flange and socket joints of two typical connected structures between cabins. First, the finite element results of a 3D fine model reveal that the static axial stiffness of the two bolted joints is asymmetric and symmetric in tension and compression, respectively. With a larger average static stiffness of tension and compression, the bolted flange joint has a higher natural vibration frequency. Then, a unified dynamic model of the two bolted joints is established, the motion of the flange joint is shown to be coupled because of the asymmetric axial stiffness. By approximating the nonlinear stiffness by high precision power functions, under the transverse dynamic load, numerical solutions of the impact response demonstrate that the frequency of the coupled longitudinal vibration is twice of the transverse frequency. Finally, for the flange joint, the double-frequency coupling longitudinal vibration is confirmed by the impact experiments. The socket joint can provide a high modal damping ratio despite the lower frequency for the first mode according to experimental results.