Study On Targeted Energy Transfer And Global Dynamics Of Bistable Vibration Absorbing Structures

In this thesis,a new grounded bistable nonlinear energy sink with light mass is proposed,the vibration reducing characteristics and effect of the NES weakly coupled to a linear oscillator are studied through the Hamiltonian topology structures and the Melnikov method.The nonlinear energy sink combined with the bistability and grounding characteristics has asymmetric characteristics,which can optimize the targeted energy transfer(TET)in the coupled system.The advantages of this new type of grounded bistable nonlinear vibration absorbing structure are highlighted by comparison with a grounded linear vibration absorbing device.The main contents are as follows:Firstly,the dynamic equations of the main structure coupled with a grounded linear damper are derived.Two linear modes of the system are discussed,and the vibration reducing mechanism of the grounded linear damping device is revealed according to the characteristics of these two linear modes.Furthermore,the vibration reducing characteristics of the grounded linear vibration absorbers are discussed through the dynamic characteristics of two kinds of linear modes.Secondly,dynamic equations of the coupled system in which the LO weakly coupled to the grounded bistable nonlinear energy sink are obtained.The capability for the grounded bistable NES to absorb the energy from the LO is evaluated by the transformed variable on the projections of the isoenergetic manifolds when the coupled system occurs1:1 internal resonance.The dynamical properties of nonlinear normal modes(NNMs)are studied by the Poincare map.In the damped coupled system TET as an irreversible energy transfer channel is realized by the jump of different NNMs.Furthermore,proper application of the asymmetric characteristics of the potential energy well will optimize the TET to achieve complete energy transfer.The response of the coupled system under impact excitation and periodic sinusoidal excitation are discussed comprehensively.Compared to the linear vibration absorber,the lightweight and broadband characteristics of this new grounded bistable NES are highlighted.