Research On Beam-rod Type Nonlinear Vibration Isolation Device Coordinating Low-frequency And Bearing Performance

With the increasingly stringent requirements for vibration environment,the demand for efficient vibration isolation technology in daily life and engineering applications is increasing.Nonlinear vibration isolators have attracted wide attention from scholars at home and abroad due to their excellent characteristics of high static stiffness and low dynamic stiffness.Based on the design idea of obtaining quasi-zero stiffness characteristics of the system by connecting negative stiffness and positive stiffness elements in parallel,several new non-linear vibration isolation devices are proposed and their vibration isolation performance is systematically studied in this paper.The purpose is to obtain stable wide-frequency and low-frequency vibration isolation performance and provide theoretical basis and reference for the design of engineering vibration isolation devices.A quasi-zero stiffness nonlinear vibration isolation device is proposed by introducing a slender beam into the design of positive stiffness components.The statics model of the device is established,and its carrying and stiffness characteristics are compared with the traditional threespring structure.It is found that this design has the advantages of strong carrying capacity and large low stiffness interval,and the structural parameter design method for obtaining low stiffness characteristics is given.The dynamic model of the isolation device is established by combining Newton’s second law and Taylor expansion technology,and the transmission rate curve of the device is obtained by using the harmonic balance method.It is found that,compared to the beam structure and three-spring structure,this device has a larger vibration isolation range,outstanding low-frequency vibration isolation performance,and better performance stability.The correctness of the theoretical calculation is validated by the vibration testing experiments.Based on the principle of lever,three nonlinear vibration isolation devices are proposed,namely lever-compression spring,lever-tension spring,and lever-beam,revealing the inherent mechanism of the lever mechanism for expanding the low-frequency working range of the vibration isolation device.The statics models of the three vibration isolators mentioned above are established,and their force-displacement and stiffness-displacement relationships are analyzed,which shows that they are superior to the traditional three-spring structure in terms of the bearing capacity and low-stiffness performance,and proves the amplification effect of lever mechanism on the low-stiffness range of vibration isolators.However,considering the poor deformation stability of compression springs and the structural heaviness of high stiffness tension springs,the lever-beam nonlinear vibration isolation device with great application potential is ultimately chosen as the research object.Through the dynamic characteristic analysis,the low-frequency vibration isolation performance of the device is evaluated,and the principles for determining design parameters under different vibration stroke conditions are provided.A low-frequency and long-stroke beam type nonlinear vibration isolation device with high bearing capacity is proposed by introducing slender beams to the design of both positive and negative stiffness components,coordinating the high load-bearing performance of the system with a significantly increased low-stiffness working range.Based on the statics and dynamics analysis,the bearing capacity and stiffness characteristics of the device and the vibration isolation performance under the underload and overload conditions are systematically studied.It is found that positive stiffness components play a major role in the load-bearing capacity of the isolation device,while the negative stiffness component design is the core way to expand the low stiffness working range of the system.Combining the double connecting rods with the movable springs,a broadband vibration isolation device that can realize the softening nonlinear characteristics is proposed.The statics and dynamic models of the device are established.Based on the statics model,the bearing capacity and stiffness characteristics of the device are studied,and it is found that the device has a high bearing capacity.According to reasonable design,the softening nonlinear stiffness characteristics can be obtained and the low-stiffness range is large.The fourth order Runge Kutta method is employed to verify the correctness of the dynamic calculation method and results in this paper,and the force transfer rate curve of the device was obtained.The influence of structural parameters on its main resonance characteristics is analyzed.The problem of hardening nonlinearity weakening low-frequency isolation performance in existing nonlinear isolators is solved.The wide-frequency isolation range is obtained.