Research On Nonlinear Vibration Isolation Characteristics Of A Circular Ring

The nonlinear stiffness can improve the low-frequency vibration isolation performance without instability,and the nonlinear damping can suppress the resonance without affecting the high-frequency characteristics.Therefore,it is an important research direction to study the dynamic characteristics and vibration isolation performance of the new nonlinear structure.It is a more direct method to realize the nonlinear vibration isolation by using the nonlinear relationship between the force and deformation of the structure with a specific shape.In this paper,the nonlinear vibration isolation system is obtained by the bending deformation of the elastic ring,and the nonlinear characteristics of the ring are used to improve the vibration isolation performance.The basic theory of nonlinear bending ring vibration isolation is put forward and studied.Based on the analysis of the static stiffness characteristics of the ring under the prestressing force,a dynamic model of nonlinear vibration isolation of the ring with prebending is established.The frequency response function and displacement transmissibility of the system are derived by using the direct motion separation method,harmonic balance method and direct numerical integration method.The stability of the nonlinear system is judged by Floquet multiplier.The complex nonlinear dynamic phenomena such as nonlinear jump,quasi period and their existing laws are analyzed.The vibration isolation characteristics of the ring under different pre bending are discussed.The influence of the geometric configuration parameters of the system on the vibration isolation system is investigated.Both the analytical and numerical results show that the reasonable optimization of different parameters can effectively improve the isolation efficiency of the vibration isolation system.The dynamic characteristics of ring vibration isolation system strengthened by nonlinear stiffness and damping are studied.Nonlinear damping is achieved by placing horizontal linear dampers.Furthermore,the horizontal stiffness is added to the ring structure to provide nonlinear stiffness,and the vibration isolation performance of the system under the excitation of foundation displacement is studied.The results show that adding horizontal stiffness to the ring vibration isolation system can effectively broaden the frequency band of vibration isolation,and the horizontal damping can suppress the peak value of resonance without affecting the high frequency transmissibility.Reasonable combination of horizontal stiffness and horizontal damping parameters can effectively improve the vibration isolation performance of the system.Shape memory alloy(SMA)rope is introduced into the ring vibration isolation system to improve the nonlinear vibration isolation performance of the ring.Based on the Bouc-Wen hysteretic characteristics of shape memory alloy rope and the restoring force surface method,the stiffness and damping coefficients are identified.The whole continuum model of transverse pull shape memory alloy ring vibration isolation system is established.The influence of different stiffness and damping coefficient of shape memory alloy on the vibration isolation system is analyzed by harmonic balance method.The vibration isolation performance of different types of shape memory alloy(NiTi7,NiTi9/NiTi1,ST49/NiTi7,ST49/NiTi1)are compared.The results show that SMA wire rope can effectively improve the vibration isolation performance of the ring,and NiTi19/NiTi1 composite SMA wire rope has the best vibration isolation effect.Finally,the experimental device of nonlinear ring vibration isolation system is designed and established.The relationship between force and displacement of the theoretical model of ring bending is verified by quasi-static test method,and the performance of ring vibration isolation under the excitation of foundation displacement is further studied.and the displacement transmissibility under three different prebending states is compared.The experimental datas show that with the increase of the preloaded mass,the resonant frequency of the isolator gradually decreases and the frequency band of the isolator becomes wider.The theoretical model,analytical method and analytical results are verified by static/dynamic experiments.