Investigation On Rigid-flexible Coupling Dynamics For Curved Beam And Plate-shell Structure Multibody System

In the research field of aerocraft and spacecraft, with the increase of the elasticdeformation, the rotating speed and the operational accuracy of the flexible appendage,the system dynamic behavior becomes more and more complicated, and the rigid-flexiblecoupling effect becomes more and more significant, which should be paid attention in theengineering application. Influenced by the combined action of environmental factorssuch as solar radiation, wind force and body inertial force, the large overall motion ofsatellite antenna, the solar panel and wind turbine blade are more easily affected by theelastic deformation of flexible appendage. It has important value to establish themultibody system dynamic equations for curved beam and plate shell structures whichare basic components of those complicated mechanical systems in order to accuratelypredict the dynamic behavior of the system.In order to improve the computational accuracy and efficiency for dynamics ofcurved beam and shell flexible multi-body system, the dynamic modeling method ofrigid-flexible coupling system based on arc coordinates is proposed, in which threereference frames (global frame, floating frame, and curvilinear frame) are used todescribe the configure of arbitrary point in the flexible body. Arc coordinate areintroduced instead of previous Cartesian coordinates for describing the elasticdeformation, and the kinematics relationship of an arbitrary point of the curved beam isestablished. Based on Green strain of spatially varying curvature beam, the nonlinearstrain-displacement relationship for plane beam with varying curvature is derived. Finite element method is used for discretization. Instead of using the previous straight beamelements, curved beam elements are proposed to approximate the curved beam withvarying curvature. Rigid-flexible coupling dynamic equations are obtained, which aresuitable for the curved beam undergoing large overall motion. For validation the presentmodeling theory, the experimental tests for curved beam pendulum are carried out for thefirst time. By comparing the experiments results and those of present linear and nonlinearmodel, the correctness and accuracy of present nonlinear model are verified. Comparisonof the simulation results obtained by linear and nonlinear models show the geometricnonlinear effect. Furthermore, comparison of the simulation results obtained by thecurved beam elements and straight beam elements verifies the quick convergence andhigh efficiency of the curved beam element.Based on the research of the curved beam, the rigid-flexible coupling dynamicequations of the cylindrical shell are established. Arc coordinates are employed todescribe the deformations, and2-D shell element is adopted for finite elementdiscretization, and then a new method for evaluating the generalized elastic forces, whichis more formalized and more easily used than the previous method, therefore, the largecalculation quantity of nonlinear stiffness matrix is avoided, and the simulation cost isreduced obviously. Great advantages can be also achieved from the present evaluation ofthe elastic forces when calculating the jacobian of the elastic forces. By the experimentof the single axis air-bearing test bed and plate structure rigid-flexible system, thecorrectness and accuracy of present nonlinear model are verified and the shortcoming oftraditional linear model is pointed out for dealing with large deformation rigid-flexibleproblem.Considering the anisotropic material and thermal effect, rigid-flexible couplingdynamic equation is build for composite shell considering thermal shock. The thermaldeformation and geometrical nonlinear effect on the rigid-flexible coupling dynamics are studied. In order to further apply the present rigid-flexible coupling dynamics modelingtheory in the engineering field, the relationship among the heat flux density and theattitude motion coordinates as well as the elastic coordinates is firstly established.Considering the coupling among the attitude motion, structural deformations andtemperature change, rigid-flexible-thermal coupling dynamic modeling method isproposed. The rigid-flexible-thermal coupling dynamic performance is analyzed bymumerical simulation, which can be used for explanation of the thermally inducedfluttering phenomena.Based on the formulation of evaluating the generalized elastic forces, a newincremental method is proposed, and jacobian of the elastic forces are derivedinnovatively. Efficient and accurate simulations of rigid-flexible coupling dynamicsystem are achieved by the present incremental method.Finally, the research work is summarized and the contributions of the presentinvestigation are concluded.