考虑螺钉预紧力的反射镜安装结构仿真及优化

Simulation and Optimization of the Mirror Assembling Structure Considering Bolt Preload

为考察某空间相机次镜背后安装螺钉预紧对反射镜面形影响,研究了反射镜在不同螺钉预紧力和重力作用下面形变化的规律,使用接触非线性有限元方法对反射镜组件进行了仿真,采用基于Zernike多项式的数据处理算法对面形数据进行了处理,得到了消除刚体位移后的面形变化规律,并对改变螺钉直径和改变连接螺钉结构形式两种优化路径分别进行了仿真。结果表明,拧紧力矩对面形的影响明显,沿径向的重力对面形的影响随预紧力矩的增大而减少,改变螺钉连接环节的结构形式对面形的影响大于改变螺钉直径。根据仿真结果对螺钉连接环节的结构进行了修改,试验测试证明改变螺钉连接环节的结构形式对于改善反射镜面形作用明显,可应用到类似反射镜结构连接的设计中。

To investigate the influence of the assembling bolt preload on the surface figure of the secondary mirror for certain space camera, the change rule of the mirror surface figure was studied under different bolt pretightening force with and without gravity using contact nonlinear finite element method. The surface displacement data were processed using algorithm based on Zernike polynomials, and then the rule of surface figure with rigid motions eliminated was obtained. To improve the surface figure quality, the bolts with different diameter parameters and bolt structure configuration were considered in the simulation. The results show that the pretightening torque has obvious influence on the surface figure, and the influence of gravity along radial direction reduces as the pretightening torque increases. Moreover, the change of bolt structure configuration has more significant influence on the mirror surface figure than the diameter change. According to the simulation result, the assembling bolt structure was modified, manufactured and assembled, and then the surface figure was measured. Experiment data indicate that the mirror surface figure quality can be improved effectively by the updated bolt structure. It should be helpful to generalize the connection configuration into other similar mirror assembles.