大口径SiC轻量化主镜的优化与有限元分析

Optimization and Finite Element Analysis of Large-Aperture SiC Lightweight Primary Mirror

为达到高度轻量化的目的,以口径为1000 mm光电经纬仪的扇型SiC轻量化主镜为研究对象。通过对主镜背部加强筋的厚度、背部半封闭型面板的厚度和主镜的总厚度进行优化,使主镜的体积和质量均减小。建立三维模型后,利用有限元软件Abaqus建立有限元模型,得到有限元仿真结果后对主镜进行变形分析。利用Zernike多项式对主镜变形数据进行拟合,得到主镜的面形误差方均根(RMS)值。仿真结果表明,在满足主镜面形精度设计要求的情况下,优化后主镜的质量为62.78 kg,相比初始质量(89.36 kg)下降30%,主镜的径厚比由8.58提高至11.44。当光轴水平时,利用四维干涉仪对扇型轻量化主镜进行面形检测,主镜面形误差RMS值的检测结果为18.22 nm。

In order to achieve a high degree of light weight,a sector-shaped SiC light-weight primary mirror of a 1000 mm photoelectric theodolite is taken as the research object and optimized design.By optimizing the thickness of the ribs on the back of the main mirror,the thickness of the semi-closed back panel and the total thickness of the main mirror,the volume and quality of the main mirror are reduced.After the three-dimensional model is established,the finite element model is established using the finite element software Abaqus,and the deformation analysis of the primary mirror is performed after the finite element simulation results are obtained.The Zernike polynomial is used to fit the deformation data of the primary mirror,and the root mean square(RMS)value of the surface error of the primary mirror is obtained.The simulation results show that the mass of the optimized main mirror is 62.78 kg,which is 30%lower than the initial mass(89.36 kg),and the diameter-to-thickness ratio of the main mirror is increased from 8.58 to 11.44 when the design requirements of the main mirror surface accuracy are met.When the optical axis is horizontal,a four-dimensional interferometer is used to detect the surface shape of the fan-shaped lightweight main mirror,and the detection result of the RMS value of the main mirror surface error is 18.22 nm.