Thermally Induced Vibrations Of Large-scale Space Multi-body Structures Based On The Absolute Coordinate

Nowadays the spacecraft is developing toward the direction of large-scale,complicated, and precise manufacturing, and thermally induced vibrations of the spacecraftare easily caused by the special space radiation, therefore, it will be crucial to accuratelypredict the thermally induced dynamics of spacecrafts during structural design. But on theground, it is very difficult and expensive to simulate the space environment of thermalradiation, microgravity, and high vacuum, so the theoretical and numerical methods have tobe used for the thermal-structural dynamic analysis of spacecrafts. Furthermore, thelarge-scale flexible structures on spacecrafts usually undergo the motions of large rotationand deformation, and the coupled thermal-structural dynamic analysis of the spacestructures with large overall motions is still lacking.In this thesis, the absolute nodal coordinate formulation is employed to analyze thedynamics of large-scale space flexible structures under the solar radiation, and the basicelements for the coupled thermal-structural dynamic analysis of the beam or plate withlarge overall motions are established. The study is developed on the basis of three typicalspace structures including the manipulator, solar panel, and spinning spacecraft, and the2-dimensional Euler-Bernoulli beam,3-dimensional laminated composite plate, and3-dimensional cross-section distortion beam elements considering thermal effect in thespace environment are developed, respectively. The research results show that: under asudden solar radiation, the thermal flutter is discovered for the fixed manipulator,cantilevered plate, and spinning spacecraft, and the deflection of a rotating manipulator andthe vibration amplitude of a translational solar panel are both increased obviously; underthe thermal load of sunrise, the acceleration response of the rigid-flexible couplingmulti-body structures consisting of the solar panel and the main body of satellite displays athermal snap characteristic; and the beating phenomenon in vibration is found for theattitude dynamics of the spin-stabilized Ulysses spacecraft. In addition, the causes ofthermal flutter are explained according to the work done by the thermal moment, and thethree conditions for causing the thermal flutter are also derived; the efficient formulations of evaluating the nonlinear elastic forces are derived using the condensed shape function,which can obviously reduce the running time of the program.Based on the absolute nodal coordinate formulation, a new three-dimensional fullyparameterized beam elements including cross-section distortion is proposed in this thesis,and the model B2in the proposed beam elements is employed to study the coupledthermal-structural dynamics of spinning spacecrafts. Firstly the position vector of any pointon the beam is given by a unified way, and the linear and high-order models of beam crosssection are proposed by means of the Pascal triangle polynomials. The research resultsshow that: the Poisson locking problem in the beam elements of the absolute nodalcoordinate formulation can be eliminated with the proposed high-order beam models; theproposed cross-section distortion beam elements can capture more accurately the structuredeformations, compared to the existing beam models, especially for the beams with largeflexibility and deformation; the fourth-order beam model can well describe the warpingtorsion and large torque deformation of a square beam; the model B2is more efficient toinvestigate most of the static and dynamic problems for a beam structure.Finally, the thermally induced vibrations of the large-scale ring truss structure of theAstroMesh under a sudden solar radiation are studied by means of the coupledthermal-structural analysis model. The thin-walled tube element considering thermal effectis developed by means of the model B1, and the enhanced continuum mechanic basedformulation is used to evaluate the elastic forces. The research results show that: the naturalfrequencies of the ring truss are very low; under the solar radiation, the thermally induceddeformations and vibrations of the structure are both very small, that is, the ring truss isextremely stabilized; but the temperature difference between the parts of the ring truss issignificant, and its maximum value is approximate to200K.