Research On Dynamics And Restraining Vibration Of Assembled Flexible Link

It is proposed that flexible link can be made assembled structure to restrain its vibration with contacting-surface damping. Assembled flexible link has effective vibration-restraining capability, simple structure, stable performance and engineering application value. Through a kind of multi-layer assembled flexible link, many problems about assembled flexible link are researched by means of experiment, theoretical analysis and finite element simulation. They include the static and dynamic behavior of assembled flexible link, its vibration-restraining capability, influence of structural parameters on its static and dynamic behavior and vibration-restraining capability, dynamic modeling, dynamics model parameter identification, and solution of dynamic differential equation, which provides principles and effective methods for research of vibration suppression of assembled flexible link,damping design and motion control. The main contents are as follows:By static bending test, load-deformation characteristics and energy dissipation characteristics are understood, and can be explained according to interaction effect of contacting-surface. On the basis of synthesizes and analyses of experimental results, load-deflection curve is simplified, and its load-deformation characteristic can be described with three parameters such as first stiffness k₁, second stiffness k2 and turning point deformation y_B.The formula about energy dissipation rate of assembled flexible link under threes deformed-conditions is obtained. The deformed state is discussed, in which assembled flexible link has maximum energy dissipation rate, and is verified by experiment.Through a lot of experiments, the influence of structural parameters such as clamping force, laminated layer stiffness, laminated layer numbers, laminated layer material, etc on load-deformation characteristic and energy dissipation rate of assembled flexible link are researched. The measures about improving energy dissipation rate and reducing the laminated quality are presented. The results provide principles for the structure design of assembled flexible link.Three kinds of dynamics models of system composed of assembled flexible link and a mass are established. Firstly, on the basis of Bernoulli-Euler beam theory, deformation relation and interactional force between main beam and laminate layers are analyzed and established, and by Newton-Euler method, continuous systems movement partial differential equation of assembled flexible link is deduced. Secondly, using equivalence principle, interaction among combination layers is equaled to bilinear hysteretic model, and shape function is introduced to describe deformation of assembled flexible link, and then according to the Hamilton principle, concentrated parameter model of system composed of assembled flexible link and a mass is established. Thirdly, using contact element to simulate interaction among layers and considering influence of large deformation on the stiffness of assembled flexible link, finite element model of the system is established.Through free vibration test and forced vibration test of assembled flexible link, it is proved that assembled flexible link can effectively restrain vibration. According to the characteristics of the response, free vibration of assembled flexible link is divided to two phases. They are fast damped vibration with changing frequency and slight vibration. The reasons of the vibration damping are analyzed, and vibration attenuation index is made.Through lots of experiments, it is researched that structural parameters influence the vibration-restraining capability of assembled flexible link, which are clamping force, friction coefficient, laminated layer stiffness, laminated layer numbers, laminated layer material, the weight of mass. The results provide principles for research of vibration suppression and damping design of assembled flexible link.By using finite element model, the simulation testing about the static and dynamic behavior of assembled flexible link is implemented. The simulation testing is consistent with experiment and can describe the static and dynamic characteristics of assembled flexible link. FEA simulation provides an effective method for damping design and research of assembled flexible link.According to FEA simulation testing instead of physical experiment, the dynamic model parameters of system composed of assembled flexible link and a mass is identified. The quartic polynomial is used to express the shape function of assembled flexible link, the coefficient of polynomial is determined according to FEA statics simulation testing. Through decomposing dynamic hysteretic restoring force curve and least-square method, the dynamic model parameters of system composed of assembled flexible link and a mass are determined.The influence of Amplitude and frequency of vibration on the dynamic model parameters is researched. The results show that dynamic model parameters of assembled flexible link are basically stable, which provides principles for the application of dynamics model of assembled flexible link.S-function blocks are written in M-file to calculate dynamic restoring force and nonlinear elastic force. The simulink model is created, and is used to solve nonlinear dynamic differential equation of system composed of assembled flexible link and mass. The results from simulink simulation are consistent with experiment. It is indicated that the method of dynamic modeling, parameter identification of dynamic model and method of dynamic equation solution are accurate and feasible, which provides an effective method for modeling and solving of system composed of assembled flexible link and mass.