Thermoelastic Behavior and Stability of the Spacecraft Booms

本文对太阳辐射加热和实验室灯加热下薄壁圆形闭截面悬臂的热致弯曲振动进行了理论分析。并通过空气和真空实验对这些结果进行了验证。首先，将具有顶部质量的均匀圆截面臂架建模为单自由度模型。控制方程是在假设臂架受单向太阳辐射加热和净吸热取决于相对于臂架的热辐射入射角的情况下制定的。考虑静挠度周围的小振动，得到了不稳定区域边界的封闭形式方程，并给出了将系统参数平面划分为稳定和不稳定区域的边界曲线。接下来，使用连续系统模型进行了类似的分析。在这种情况下，求解…More的方法包括对方程和时变边界条件应用关于时间的拉普拉斯变换，并通过对变换后的解进行数值反演来获得响应。此外，考虑重力的影响，假设臂架表面的辐照量与臂架的挠度成正比，建立了实验室条件下实验的基本方程。通过室内空气条件下的实验，验证了辐射加热引起的热致弯曲振动的发生。薄壁圆截面悬臂由不锈钢制成，顶部有质量，由红外灯加热，红外灯用作单向辐射源。测量了悬臂叶顶位移的响应，结果表明，当辐照强度较大时，悬臂梁确实会产生自激弯曲振动。热激振动的频率、稳定性边界和由总阻尼比表示的不稳定性特征与理论预测结果吻合较好。最后，利用大型真空室在真空条件下进行了类似的实验。得到了臂架表面扰动温度响应的相位角与臂架尖端偏转响应的关系，从而明确了臂架的热致弯曲振动是由于温度波动在90℃附近存在相位滞后而引起的非定常热弯矩引起的。少

Theoretical analyses of the thermally induced bending vibration of the thin-walled circular closed section boom are presented for both the cases heated by solar radiation and by a lamp in the laboratory.And experimental verifications of these results are carried out by both the experiments in air and in vacuum.First, uniform circular section boom with a tip mass is modeled as a single-degree-of-freedom model. The governing equations are formulated assuming that the boom is heated by the unidirectional solar radiation and that net heat absorption depends on the angle of incidence of heat radiation with respect to the boom. The closed form equation of the boundary of unstable region is obtained by considering the small vibration around the static deflection, and the boundary curves which divide the system parameter plane into regions of stability and instability are also presented. Next, similar analysis is presented using the continuous system model. In this case, the method of solution … More consists of applying the Laplace transform with respect to the time to the equation and to the time-dependent boundary conditions, and of obtaining the response by a numerical inversion of the transformed solution. Furthermore, the basic equations for the experiments under the laboratory conditions are also formulated by taking account of the effect of the gravity and assuming that the irradiation of the boom surface changes proportional to its deflection. An occurrence of the thermally induced bending vibration caused by radiant heating is verified by the experiment under laboratory conditions in air. Thin-walled circular section boom made of stainless steel with a tip mass is heated by an infrared lamp which is used as a source of the unidirectional radiation. Responses of the tip displacement of the boom are measured and it is shown that the self-excited bending vibrations can occur actually when the irradiation is large. Frequencies of the thermally induced vibrations, the stability boundaries and the instability characteristics presented by the total damping ratio are well consistent with the theoretically predicted results. Finally, similar experiments are carried out in vacuum making use of the large vacuum chamber. The relations of the phase angle in responses of the perturbation temperature of the boom surface and of the tip deflection of the boom is found, and then it is clarified that the thermally induced bending vibration of the boom is caused by the unsteady thermal bending moment due to the temperature fluctuation having the phase lag near 90ﾟ. Less