Design of high volume fraction SiC/Al composite mirror in space remote sensor
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摘要: 为消除反射镜与支撑结构材料线胀系数差异产生的热变形对反射镜面形精度、系统成像质量的影响, 采用高体份SiC/Al复合材料作为新型反射镜组件的材料。首先, 通过合理的结构设计及有限元分析比较, 确定了Ф600 mm口径反射镜结构参数, 然后, 对反射镜组件进行了静力学和动力学分析, 在1 g重力载荷作用下, 反射镜X、Y、Z方向去除刚体位移后的镜面变形RMS值分别为12.6, 12.7, 12.6 nm, 达到了λ/50(λ=632.8 nm)。最后, 为了验证高体份SiC/Al复合材料反射镜组件的结构性能及检验结构在振动条件下的抗干扰能力, 对反射镜组件进行了力学试验, 反射镜组件的一阶谐振频率为556.6 Hz。力学试验前后, 反射镜镜面面形误差RMS分别为0.021λ、0.025λ, 没有明显变化。实验结果表明:高体份SiC/Al复合材料反射镜达到了与SiC材料反射镜相同的设计指标要求, 能够满足空间应用。
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关键词:
- 空间遥感器 /
- 空间反射镜 /
- 高体份SiC/Al复合材料 /
- 有限元分析
Abstract: The difference of linear expansion coefficient between a mirror and its support structure causes mirror thermal deformation which influences the surface accuracy of mirror and the image quality of optical system. In order to avoid above influence, the high volume fraction SiC/Al composite is chosen as the only material of a Φ600 mm mirror component. The Φ600 mm mirror structure parameters are specified by the reasonable mechanical design and finite element analysis. Using finite element analysis method, the static and dynamic characteristics of the mirror component are analyzed. Under the gravity load of 1 g, the surface figure accuracy of the high volume fraction SiC/Al composite mirror reaches RMS 12.6 nm, 12.7 nm, 12.6 nm, in X, Y, Z respective direction, nearly λ/50(λ=632.8 nm). The mechanical dynamic test results verify the structural performance and the capability of vibration resistance. The 1st order natural frequency of the mirror component is 556.6 Hz. After the test, the surface figure accuracy changs from RMS 0.021λ to 0.025λ, not showing obvious changes. The high volume fraction SiC/Al mirror can reach the same design indexes as SiC mirror and meet the space application requirements. -
图 3 不同镜体厚度、面板厚度的反射镜镜面面形变化曲线
Figure 3. Curves of mirror deformation with different mirror thickness and plate thickness
图 4 镜面面形随不同筋板厚度的变化曲线
Figure 4. Curve of mirror deformation with different rib thickness
表 1 常用反射镜材料的性能
Table 1. Performance of rational materials for mirror
光学材料 密度/ (g·mm-3) 弹性模量/ Gpa 比刚度 热膨胀系数 10-6/K 导热系数/ (W·m-1·K-1) 比热容/ (J·kg-1·K-1) 热稳定性 铍 1.85 287.00 155.14 11.40 216.00 1 925 18.95 硅 2.33 131.00 56.22 2.60 137.00 710.00 52.69 碳化硅 3.20 400.00 125.00 2.40 155.00 650.00 64.58 高体份SiC/Al 3.00 180.00 60.00 8.00 225.00 715.00 28.13 
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表 2 不同反射镜厚度、面板厚度面形分析统计
Table 2. Mirror surface figure of different plate and mirror thickness(Unit: nm)
面板厚度/mm 反射镜厚度/mm 100 110 120 130 140 150 160 170 3.0 8.34 8.07 7.79 7.68 6.92 6.76 6.62 6.49 3.5 7.97 7.39 7.12 7.00 6.2 6.05 5.90 5.77 4.0 7.98 7.37 6.93 6.55 5.71 5.56 5.32 5.18 4.5 8.09 7.48 7.03 6.65 5.35 5.17 5.03 4.89 5.0 8.19 7.58 7.04 6.66 5.437 5.03 4.78 4.60 5.5 8.30 7.69 7.15 6.76 5.437 5.13 4.82 4.52 6.0 8.40 7.79 7.25 6.86 5.54 5.13 4.83 4.52 6.5 - - - - - - - 4.63
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表 3 不同筋板厚度面形分析统计
Table 3. Mirror surface figure of different rib thickness
筋板厚度/mm 面形PV值/10-8 m 2 5.664 2.5 5.439 3 5.432 3.5 5.437 4 5.432 4.5 5.339 5 5.432 5.5 5.435 6 5.538 6.5 5.536 7 5.540 7.5 5.645
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表 4 反射镜组件前3阶模态
Table 4. First 3-order modes of mirror component
阶次 频率/Hz 振型 1 591 反射镜沿着x轴摆动 2 662 反射镜绕着x轴转动 3 666 反射镜绕着y轴转动
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