大型航天器结构的热致振动研究

摘要

多数航天器在轨服役期间会受到冷热交变热辐射载荷作用而出现热致振动问题，因此，在结构设计阶段准确地预测热诱发的航天器动力学行为至关重要。基于绝对节点坐标方法，并采用耦合的热-结构分析模型，建立了可以对大范围运动的薄壁管和复合材料层合板进行热-动力学耦合系统分析的非线性有限单元，同时基于浓缩的形函数推出了非线性弹性力的高效计算公式。利用所建单元，针对受到太阳辐射热冲击载荷作用的航天器结构展开研究。首先，研究了经典的悬臂梁和板结构的热致振动，其位移响应都出现了不稳定的热颤振现象，并从热弯矩做功角度解释了产生热颤振的原因；然后，又研究了UARS卫星和Ulysses自旋稳定航天器的热致振动，将它们简化为刚-柔耦合的多体系统动力学模型， UARS的加速度响应出现了热跳变现象，而Ulysses的姿态角响应出现了热拍现象；最后，研究了大型环状天线的桁架结构及其支撑机械臂结构，热变形和振动幅值都较小，即结构较稳定。%Thermally induced vibrations are generated by the heat radiation with cold and hot alter-nation for most of the spacecraft structures in orbit.Therefore, it is crucial to accurately predict the thermally induced spacecraft dynamics during the structure design.In this paper, the nonlinear fi-nite elements of the thin-walled tube and laminated composite plate which may have large overall motions were established based on the absolute nodal coordinate formulation and the coupled ther-mal-structural model to analyze the coupling effect between heat transfer and dynamics.In addition, the efficient formulation for evaluating the nonlinear elastic forces was derived by means of the con-densed shape function.The spacecraft structures, under the thermal shock from solar radiation, were studied using the established elements.Firstly, thermally induced vibrations of the classical cantilevered beam and plate structure were considered.There were both thermal flutters for the dis-placement responses, and the causes of the phenomenon were explained according to the work done by the thermal moment.Secondly, the UARS satellite and Ulysses spinning spacecraft were also studied, in which they were simplified into a rigid-flexible multibody system.There were thermal snap and beating for the UARS acceleration and Ulysses attitude angle responses, respectively.Fi-nally, the truss of a large reflector and its supporting arm were investigated.For the truss and arm, the amplitudes of thermally induced deformations and vibrations were both very small, that is, the structure was extremely stabilized.