Mechanical properties analysis of a 20 cm diameter ion thruster
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摘要: 为了提升20 cm离子推力器的抗冲击性能，对现有结构开展了力学分析和试验验证。对栅极组件进行结构等效处理后，采用有限元方法分析了整机的模态和冲击响应谱。分析结果显示，栅极组件结构等效前后的分析结果对比差距8.3%～11.9%；推力器的3个轴向基频分别为246，248，336 Hz，栅极组件和中间极靴是离子推力器的力学薄弱环节并对整体结构稳定性具有重要影响；在冲击载荷1600 g下，栅极组件表面应力主要集中在小孔区边缘处，且形变也主要发生在小孔区；在采取刚度为1000 kN/m的减振措施后，栅极组件的整体形变位移降低了60%～82%。试验结果显示，在10～1200 Hz的低频扫描过程中，推力器3个轴向的基频分别为256，258，348 Hz，与仿真结果基本一致，采用减振措施后的20 cm口径离子推力器通过了1600 g的冲击试验。
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关键词:
- 离子推力器 /
- 力学特性 /
- Von-Mises应力 /
- 形变位移
Abstract: To improve the anti-mechanical performance of the 20 cm diameter ion thruster, the mechanical analysis and experimental verification of its existing structure were carried out. After the grids were handled equivalently, the modal analysis and impact response spectrum analysis of ion thruster were carried out based on finite element analysis. The modal analysis results were validated by the fundamental frequency sweep test. Finally, the impact response of the thruster after adopting the damping structure was simulated and verified by experiments. The obtained results indicate that after the grids assembly being handled equivalently, the analysis results’ difference are about 8.3%−11.9%. The modal analysis result shows that the base frequencies of the thruster in the x, y and z directions are 246, 248 and 336 Hz respectively. The grids and middle magnet pole are the weak links in the mechanics of the ion thruster and affect the overall structural stability. The 1600g response spectrum analysis results indicate that 1600g, the surface stress of the grids concentrates on the rim of the aperture region, furthermore the deformation largely occurs in this region. When the vibration damping effect with the stiffness of 1000 kN/m is taken, the overall deformation of the grids is reduced by 60%−82%. Mechanical test results show that, during the low-frequency scanning process of 10−1200 Hz, the base frequencies of the thruster x, y and z directions are 256, 258 and 348 Hz respectively, basically consistent with the simulation results. Secondly, the 20 cm diameter ion thruster with damping measures passed the 1600 g impact test.-
Key words:
- ion thruster /
- mechanical properties /
- Von-Mises stress /
- deformation
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图 2 加速栅不同结构下的x方向形变量和Von-Mises应力分布
Figure 2. x-direction deformation and Von-Mises stress of different accelerator grid structure
图 5 20 cm离子推力器预应力和形变分析结果
Figure 5. Pre-stress and pre-deformation of 20 cm ion thruster
图 6 冲击载荷下栅极组件z方向Von-Mises应力分布及形变量
Figure 6. z-direction Von-Mises stress and deformation of the grids under impact load
图 7 增加减振措施后的栅极z方向Von-Mises应力及形变的冲击响应分析结果
Figure 7. z-direction Von-Mises stress and deformation of the grids by elastic support under impact load
图 8 x方向基频扫描结果和1600 g冲击载荷试验结果
Figure 8. x-direction fundamental frequency and response spectrum
表 1 20 cm离子光学系统结构等效后的材料力学特性
Table 1. Effective property of the grids of 20 cm ion thruster
component material transparency effective density/(kg·m−3) effective Young’s modulus
/GPaPoisson ratio the screen grid Mo 0.69 2973 99.2 0.31 the accelerator grid Mo 0.27 7001 233.6 0.31 
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表 2 不同加速栅有限元模型下的模态分析结果对比
Table 2. Comparison of modal analysis for different FEM models of the accelerator grid
structure modal analysis results of the accelerator grid/Hz 1st step 2nd step 3rd step 4th step 5th step 6th step with-aperture (reality) 51.815 207.55 251.89 303.24 427.88 474.92 without-aperture (effective) 47.193 194.05 237.34 293.65 405.02 453.04
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表 3 20 cm离子推力器不同部件的材料力学属性
Table 3. Different components material property of 20 cm ion thruster
components material density/(kg·m−3) Young’s modulus/GPa Poisson ratio extension strength/MPa mount ring 2A12 2700 72 0.31 265 up/down harness 2A12 2700 72 0.31 265 magnet (effective） — 4105 72 0.31 265 up/down magnet pole DT4 7830 81 0.29 170 hollow cathode 1Cr18Ni9Ti 7930 193 0.31 200 bolts TC-4 4620 96 0.34 825
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表 4 推力器前6阶模态分析结果及不同方向的有效质量百分比
Table 4. Primary 6 step modal frequencies and effective mass percentage of thruster
modal frequency/Hz x-direction/% y-direction/% z-direction/% 1 246.066 35 1 1 2 248.167 1 37 0 3 338.722 4 0 50 4 404.484 0 17 0 5 411.324 15 0 3 6 605.016 0 0 1
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