Finite Element Modeling Of Deployment Dynamics Of Space Structures Via Isogeometric Analysis

In recent years,some challenging missions have been proposed in aerospace science and technology,such as the high-precision observation,the large-capacity communications and the deep space exploration.In order to achieve these aerospace goals,the large-scale space deployable structures play an important role in future space activities.In general,the scale of the space structure is much larger than the diameter of the launch vehicles.Therefore the space structure should be folded before launching the spacecrafts.After the spacecrafts injection into orbit,the space structures are deployed.During the deployment progress of the space structure,the large-scale movement of the flexible components is coupled with the large deformation,which is the typical dynamic characteristic of the flexible multibody system.Restricted by the laboratory facility and the cost of the experiments on ground,such as microgravity and heat exchange,modeling and simulation based on the dynamics of flexible multibody systems is an irreplaceable part in the research and development of the large-scale space deployable structures.In the last two decades,the research in flexible multibody dynamics has made substantial progress,in particular,the nonlinear finite element represented by the Absolute Nodal Coordinate Fromulation(ANCF)has been widely applied to deal with the deployment dynamics of the large-scale space structures.However,in this formulation the slope vectors are selected as the element node coordinate,the increased scale of the freedoms for the complex structures gives rise to the computational burden.While in recent years,the Isogeometrical Analysis(IGA)emerging in computational mechanics has provided a new approach to solve the above problems.Based on this method,not only the large rotation and large deformation of flexible components can be captured with high convergence,but also the geometric features can be described accurately with fewer freedoms.However,using this method to study the dynamics of flexible multibody systems in the deployment of large-scale space structures,there are still some open problems,such as adequate finite elements for very soft components,efficient computation schemes and local refinement for the complicated flexible components.Based on the above issues,several new finite elements and calculation methods havebeen proposed in the frame of the IGA.Besides,the form-finding analysis and design of the mesh reflectors are stuied.Furthermore,the dynamics simulation of the modular space deployable antenna is also researched.The major contributions of the dissertation can be summarized as follows.1)To model the slender beam and thin shell structures with exact geometry,the beam and shell elements described with NURBS curves and the tensor product NURBS surfaces have been proposed in the frame of IGA.Based on the total lagrangian formulation,the deformation of the elements is described with the Green strain,and the strain energy of the elements can be obtained.Besides,the elastic force and its Jacobian matrix of the elements are also deduced.2)In order to solve the deficiency of the local refinement with tensor product splines in IGA,three geometrically exact triangular shell elements are proposed based on the cubic triangular Bézier surface patches.The linear mapping between ANCF triangular elements and triangular Bézier surface patches is established.To guarantee the continuity of the approximate geometric G~1,the constraint conditions between the adjacent patches are discussed.Besides,the possion locking problem of the fully parameterized element can be relieved with the quadratic polynomial interpolation along the shell thickness direction.3)In order to expand the IGA with triangle topological splines,the reproducing kernel triangle elements based on the triangle B-spline surface are implemented.A reproducing kernel skill is introduced to improve the computation stability and accuracy of the triangle B-spline basis,and the consistency condition can be observed,thus improving the convergence of the triangle B-spline elements.The correctness and convergence of the proposed elements are verified with some numerical examples in the end.4)Based on the Force Density Method(FDM),an effective and universal form-finding method of the mesh reflectors for the modular space deployable antenna has been proposed.Using this method,the form-finding analysis of the modular mesh reflector is performed and the form-finding results provide a reference for the manufacturing and infrastructure of the mesh reflector.5)Based on IGA and ANCF,A rigid-flexible coupling dynamics modeling of the modular space deployable antenna reflector is established.The dynamics response of the support truss and cable-net during the deployment process is analyzed.In addition,the excessive cable tension in the stowed configuration of the mesh reflector is also studied.The results provide the theoretical foundation for the deployment research of the multi-module antenna reflectors.