空间SiC反射镜背部中心支撑特性

基于特定的轻量化形式和支撑结构,采用有限元方法研究了口径为500mm的空间SiC反射镜的背部中心支撑特性.通过分析镜体结构参量对反射镜性能的影响,确定了最佳的支撑孔直径与反射镜口径的比例为0.23,指出对不同口径的反射镜需通过优化确定最佳的背部形状,当重力沿径向作用时,增大支撑深度有利于提高面形准确度.支撑结构分析结果表明,柔性连接件底部螺栓圆半径是影响温变载荷工况下的面形准确度和反射镜组件的一阶固有频率的关键因素,要确定最佳的底部螺栓圆半径需综合考虑面形准确度和结构基频两方面的指标要求;背部中心支撑的反射镜面形准确度受外界装配应力的影响较小,且对柔性连接件切槽深度的变化不敏感;支撑长度主要影响结构的动态刚度,减小支撑长度能提高反射镜组件的一阶固有频率.最后确定了空间SiC反射镜背部中心支撑的最大适用口径为750mm,对口径小于750mm的SiC反射镜在结构允许的前提下采用背部中心支撑均能满足设计要求.

Characteristics of Rear Support in Centre for Space SiC Mirror

Taking a SiC mirror with an aperture of 500mm for example,the supporting characteristic of rear support in centre was studied based on spercific lightweight shape and supporting structure by using finite element analysis,and the effects of structural parameters on the performance were analyzed.The analyses point out that the optimal proportion of the diameter of support hole to the aperture of mirror is 0.23,the optimal rear shape of mirror with different aperture should be determined by using optimization method,and the surface accuracy can be improved by increasing the support depth when the gravity in radial direction.The analyses of supporting structure indicate that the radius of bolt circle at the bottom of the flexible connector is the key factor which has great influence on both the surface accuracy under the load case of temperature variation and the first order frequency of mirror subassembly,so it is considerable to weigh the requirment of surface accuracy and structural basic frequency when chosing the optimal value of the radius.The surface accuracy of the mirror supported by rear in centre is less affected by the assembling stress from outside and not sensitive to notch depth changing.The support length has a great influence on dynamic stiffness of the structure and its decrease will increase the first order frequency of mirror subassembly.Finally the maximum aperture of the space SiC mirror supported by rear in centre is intended to be 750 mm,which means that the mirror supported by rear in centre without of structural constraint can be satisfied with the refered requirment when its aperture is less than 750 mm.