| The space-expandable structure undergoes a complex thermal environment with alternating heat and cold during the operation of the track,undergoes a temperature field that changes with time,and generates a time-dependent temperature gradient within the structure,resulting in thermal deformation and thermally induced vibration of the structure.Under the complicated thermal environment,it will affect the dynamic characteristics of the space expandable structure and affect its normal operation.In order to study the structural vibration induced by space thermal loads,the near-earth orbits are divided into orbits of different time periods and different regions.In combination with the near-earth orbital parameters,the spatially-extended heat flow changes of space-expandable structures during orbital operations are obtained.Then,the finite element model of a single-joint spatial expandable structure considering the thermal-gap is established,a reasonable simulation boundary is set,and the solution conditions are established.Using the spatial heat flow data obtained from the analysis of the thermal environment,the initial conditions of the simulation and the external load are set.The transient temperature field of the whole structure is obtained by the solution of the load,and the temperature gradient of the induced structural thermal deformation is obtained.The finite element analysis was performed on joints with gaps,and the law of heat transfer and the variation of clearance values of the joints with clearance under the influence of the main heat flow load were obtained.Subsequently,the temperature,velocity and acceleration cloud diagrams of the spatially expandable structure are analyzed,and combined with their respective time history graphs,the influence of thermal-gap on the dynamic characteristics of the spatially expandable structure is analyzed.Through the finite element simulation comparison of the spatial expandable structures with different gap values in the hinge part,the influence of hinges with different clearance values on their vibration characteristics is obtained.Based on the analysis of the dynamic characteristics of the space expandable structure with hinges,the dynamic characteristics of the thermal-gap coupling are studied.The analysis of the time history curve of the speed and acceleration of the structure during an entire cycle of on-orbitoperation gives the effect of the thermal-gap on the dynamic characteristics of the overall structure.Then,the simulation results of the time history curve of speed and acceleration under multi-period conditions are analyzed,and the influence of the thermal-gap coupling on the dynamic characteristics under multiple cycles is obtained. |
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