Thermoelastic Behavior and Stability of the Spacecraft Booms

在实验室条件下，分别在太阳辐射加热和灯加热两种情况下，对薄壁圆形封闭截面臂架的热致弯曲振动进行了理论分析，并在空气和真空中进行了实验验证。建立了控制方程，假定吊杆受到单向太阳辐射的加热，净吸热量取决于热辐射相对于吊杆的入射角。考虑静挠度附近的小振动，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区域和不稳定区域的边界曲线。接下来，利用连续系统模型进行了类似的分析。在这种情况下，解决…的方法更多的是将关于时间的拉普拉斯变换应用于方程和依赖于时间的边界条件，以及通过对变换后的解进行数值反演来获得响应。此外，还建立了实验室条件下实验的基本方程，考虑了重力的影响，并假定吊臂表面的照射量与其挠度成正比。实验室空气条件下的实验证实了辐射加热引起的热致弯曲振动的发生。具有顶端质量的不锈钢薄壁圆形截面吊杆由红外灯加热，作为单向辐射的源。测量了吊臂顶端位移的响应，结果表明，当辐照较大时，实际上可以发生自激弯曲振动。用总阻尼率表示的热激振动频率、稳定边界和失稳特性与理论预测结果吻合较好。最后，利用大型真空室进行了类似的真空实验。找出了动臂表面摄动温度响应中的相位角与动臂顶端挠度的关系，阐明了动臂的热致弯曲振动是由于温度起伏引起的非定常热弯矩引起的，其相位滞后在90ﾟ左右。较少

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