Thermal Deformation And Buckling Analysis On Large Space Structures Including Thin-walled Open Section Beam

Thermal buckling is a common problem for space structure design. Thisproblem is especially dominative for large flexible space structures, whichconsist of thin-walled open section beams. However, the mechanism ofthermal buckling with coupled bending-torsional mode has not beencompletely clarified. This paper illustrates that the characteristic of thethin-walled open section beam must be considered to study this problem.A kind of two nodes thin-walled open section beam element with warpingdegree of freedom is developed in this paper. This element is capable ofanalyzing the restricted torsion and the coupled bending-torsional deformation.Moreover, in the large deformation analysis, the thermal stress is consideredin the geometric stiffness matrix.Combining this element and other traditional beam elements, a FiniteElement (FE) scheme is developed to compute the thermal-inducedbending-torsional deformation and the thermal buckling of large space trussstructures. The thermal deformation analysis considers the thermal-inducedmoment and bi-moment, which are caused by the non-uniform temperaturefield on the cross-section of the beam;while the thermal buckling analysis isbased on a given mode of temperature field. The above methods have beencoded into a FE program, and several numerical computations are conducted.Firstly, a simple example with one beam is computed. The resultingcritical temperature and the buckling modes are in good agreement with thesolutions of ANSYS. This illustrates that this element is suitable and reliablefor this kind of applications. This example also reveals that the thermalbending-torsional mode will occur earlier than the bending mode. This is dueto the characteristic of thin-walled open section beam.Further more, the large deformation and buckling analysis are conductedfor a simplified model of the solar array on the Hubble Space Telescope(HST). The displacement and the critical prestress obtained by the presentnumerical method are approximately coincident with the ones from thetheoretical method mentioned in the references. This further illustrates thevalidity of the present FE scheme. Finally, the cause of the torsional bucklingobserved on the HST solar arrays is explained based on the thermal bucklinganalysis using the same process.