Investigation On Simulation And Experiment Technique For Rigid-Flexible Coupling Dynamic System With Large Deformation

In this dissertation, the dynamic modeling theory and experiment of rigid-flexible coupling systems are studied extensively.Based on Euler-Bernoulli assumption and Kirchhoff assumption, absolute nodal coordinate formulation is used to establish rigid-flexible coupling dynamic equations for a rectangular beam with large deformation and a rectangular plate with large deformation, in which geometric nonlinear effect is taken into account. Experiment of the rigid-flexible coupling system with large deformation is designed to verify the correctness of the complete nonlinear model by comparison of the theoretical and experiment results. Furthermore, applicability of one-order approximate nonlinear model based on small deformation theory is investigated. The main contents are described as follows:In chapter 1, the engineering application background and the significance of the research work on the dynamic modeling theory of rigid-flexible coupling system are introduced. The research development of the theoretical analysis and experiment investigation for rigid-flexible coupling dynamics is reviewed. In addition, the research trend and important problems of the rigid-flexible coupling system are put forward, and the objective of the research is proposed.In chapter 2, based on nonlinear relation between Green strain and displacement, complete geometric nonlinear model for an elastic beam is established by using absolute nodal coordinate formulation. Firstly dynamic variational equations are derived, and then considering structural damping, rigid-flexible coupling dynamic equations for the multi-body system composed of air-bearing test bed and elastic beam are derived.In chapter 3, simulation and experimental research on hub-beam system with large deformation are carried out. Experiment of the rigid-flexible coupling system composed of an air-bearing test bed and a rectangular beam with large deformation is designed and structural damping is taken into account and measured. By using the non-contact motion measuring instrument and strain measuring instrument, velocity, angular velocity and strain of points of the beam are measured to verify the correctness of the complete nonlinear model by comparison of the theoretical and experiment results. Furthermore, applicability of one-order approximate nonlinear model based on small deformation theory is investigated. By comparing the theoretical and experiment results, we found that, the results of the complete nonlinear model of this dissertation, the one-order approximate nonlinear model and the experiment make no difference while the initial tip deflection is 0.1m, thus verified the correctness of the complete nonlinear model and the correctness of the one-order approximate nonlinear model in case of small deflection. It is considered as large deflection issue while the initial tip deflection increases to 0.25m, which is greater than 10% of the beam length. The result showed that, the complete nonlinear model agrees well with the experiment while the one-order approximate nonlinear model makes great difference with the experiment. So we concluded that, the complete nonlinear model can be used in case of small and large deflection while the one-order approximate nonlinear model can be used only in case of small deflection. The numerical error of the one-order approximate nonlinear model can not be ignored when the deflection is greater than 10% of the beam length.In chapter 4, based on Kirchhoff assumption, nonlinear relation between strain and displacement as well as exact curvature expression, dynamic variational equations for a rectangular plate with large deformation are established, in which the shear strain is ignored. Considering structural damping, rigid-flexible coupling dynamic equations for the multi-body system composed of air-bearing test bed and elastic beam are derived.In chapter 5, rigid-flexible coupling dynamic analysis for hub-plate system with large deformation are carried out. By using the non-contact motion measuring instrument and strain measuring instrument, velocity, angular velocity and strain of points of the plate are measured to verify the correctness of the complete nonlinear model by comparison of the theoretical and experiment results.In chapter 6, by using absolute nodal coordinate formulation, more complete nonlinear dynamic model for a rectangular plate with large deformation is established, in which both shear strain and transverse normal strain are taken into account. On this basis, the Lagrange equations of the first kind of the rectangular plate with large deformation are established by leading into the kinematic constraint equations. Simulation of a plate applied with gravitational force shows that the total energy converges to zero, which shows the stable characteristics of the numerical results. The results of the simulation example of two rectangular plates with large deformation show that with the increase of the flexibility of the thin plate, the coupling of the longitudinal deformation in low frequency and the transverse deformation in high frequency is more significant.In chapter 7, the investigations of rigid-coupling dynamics in this dissertation are summarized and the prospect of the research is proposed.