A Study On The Dynamic Modeling And Simulation For The Rigid-flexible Coupled System Based On Meshless Methods

In the field of engineering,complicated systems are usually composed of a plurality of independent objects,which are connected by a series of geometric constraints and able to complete expected actions.Among all of these,many of them are the flexible appendages attached to the rigid body,which we called rigid-flexible coupled structures,such as space robotic manipulators,satellite antenna,helicopter rotors,solar energy panels and aircraft engine blades and so on.All the actual engineering problems above can be simplified to a rotating hub-beam systems or rotating cantilever plate model to make dynamic analysis.And what will have a major impact to the accuracy and computational efficiency of the simulation is whether we could describe the deformation field of flexible body correctly and reasonably.Therefore,the study of the discrete method of deformation field has always been the central issue and the most tough step when we are making the dynamic analysis of rigid-flexible coupled system.And also it is the urgent requirement in engineering and scientific fields.In this dissertation,a research has been made on the discrete method of rigid-flexible coupled system dynamics.In order to enrich the discrete method of the flexible multibody system dynamics,the meshfree or meshless method which has a rapid development in recent years,is introduced to the rigid-flexible coupled system dynamics.Based on the floating frame of reference formulation,use the point interpolation method,radial point interpolation method,node-based smoothed point interpolation method,finite element method and the assumed mode method to describe the deformation field of hub-beam system and make them the unified expression.The dynamic equations for a flexible hub-beam system with large overall rotating motion are established by the second Lagrange equations.The simulation results which are obtained by using these discrete methods are compared in the field of computational accuracy and efficiency to verify the accuracy and replicability of meshless method and explain the disadvantages of the assumed mode method.What's more,three time integration methods which are used to solve dynamic equations are analyzed,and their computational efficiency is compared.The modeling theory for a rectangular plate with large overall motion is studied.Baesd on classic thin plate theory,the first order approximate rigid-flexible coupled dynamic model is established by using the assumed mode method and finite element method with rectangular elements and triangular element.Based on Mindlin plate theory,the deformation field of flexible plate is described by using the radial point interpolation method,moving least squares method and smoothed finite element method.Considering the coupling deformation and its high order terms,the first order approximate rigid-flexible coupled dynamic model and high order rigid-flexible coupled dynamic model of plate with arbitrary thickness ratio undergoing large overall rotating motion are established.Using the radial point interpolation method and smoothed finite element method based on Mindlin plate theory to simulate a cantilever plate undergoing large overall motion and compared with the assumed mode method and finite element method based on classic thin plate theory.The methods to avoid shear locking phenomenon are also provided.Meanwhile,the differences among the zeroth order model,the first order approximate model and the high order approximate model are compared and their scope of application are also discussed.The free vibration characteristics of a rotating cantilever thin plate at constant speeds are investigated,especially for the influence of different structure parameters and the curve veering phenomena of the system.