Dynamic Analysis Of Spinning Flexible Structures

In recent years, spinning flexible structures have been widely used in the field of aviation,aerospace, and energy. The flexible structures not only undergo large overall rotations, but also sufferfrom the structural vibrations induced by the unbalanced centrifugal forces and aerodynamic forces.The coupling of rigid motions and elastic vibrations of the flexible structures will lead to complexdynamic characteristics. This makes that it is difficult to model and analyze the flexible structures. Thedynamic modelling of the spinning flexible structures and predicting their dynamic responses are ofgreat scienctific significance and practical value.Previous studies have indicated that the conventional modelling motheds of structural dynamicsand flexible multibody dynamics based on the assumptions of small deformations can not lead to theaccurate descriptions for the nonlinear dynamic characteristics of the flexible structures undergoinglarge overall rotations, while the Absolute Nodal Coordinate Formulation (ANCF) can accuratelydescribe the coupled dynamics of the flexible structures with large rotations and large deformations.Futhermore, the Absolute-Coordinate-Based (ACB) method, which combines the Natural CoordinateFormulation (NCF) describing rigid bodies and the ANCF describing flexible bodies, can well describethe dynamics of rigid-flexible multibody systems. However, this method still surfers from some openproblems, such as efficient computation schemes for complicated structures and adequate finiteelements with internal damping, when it deals with the dynamics of spinning flexible structures.By modeling the flexible structures by using the ANCF, this dissertation studies the dynamiccharacteristics of two specific kinds of spinning flexible structures: the rotating thin plate and thespinning deployable solar sail. The major contributions of the dissertation can be summarized asfollows.1. The ANCF finite elements of reduced beam and plate elements which can be solved in acomputational efficient way are proposed. The analytical expressions of elastic forces andJacobian matrices are derived. The static deformation examples are used to verify the validation ofthe elements.2. The modal analysis of a rotating plate is studied by using the ANCF thin plate element. Theobtained results are compared with the ones obtained by the conventional method and thecommercial software. The eigenvalue loci veering and crossing phemomena caused by thevariation of rotations are observed. The effect of rotational angular velocities on the frequencies and the modes of the rotating plate are discussed.3. The dynamic responses of the rotating thin plate by using the ANCF are analyzed. The dynamicstiffening of the thin plate is studied. It is concluded that the ANCF is more efficient in thedynamic analysis of flexible structures undergoing large rotations and large deformationscompared with the conventional methods.4. By combining the NCF and the ANCF, the spinning deployment process of a large flexible solarsail structure is studied. The simplified IKAROS solar sail system is established. The second stagedeployment of the system is also studied. The effects of the tip mass and the initial spin rate on thedeployment are analyzed.5. A viscoelastic ANCF finite element of thin plate is proposed. By combining the viscoelastic cableelement, the second stage deployment of the simplified IKAROS solar sail system withviscoelastic damping is studied. The effect of the viscoelastic damping on the deployment isdiscussed.