Design And Analysis Of Quasi Zero Stiffness Vibration Isolator With Adjustable Load-bearing Capability

At present,vibration isolation design is an important guarantee for the stable operation of vehicle mounted precision instruments.The traditional linear vibration isolation system can effectively isolate the medium and high frequency vibration,and the low frequency vibration isolation is a difficult problem in the field of vibration control.In recent years,some no nlinear shock absorbers emerge as the times require.Among them,the quasi zero stiffness vibration isolation system can not only meet the needs of low-frequency vibration isolation,but also has strong bearing capacity without energy input,so it has a good development prospect.However,the current structure of quasi zero stiffness isolator is large in size and prone to instability due to load variation,which limits its application in practical engineering.Therefore,based on the nonlinear vibration numerical analysis method and finite element simulation method,this paper designs a load-bearing adjustable quasi zero stiffness isolator by paralleling the non-standard opening disc spring negative element,the cylindrical rubber spring positive element and the opposite inclined spiral spring adjusting mechanism.The analysis results show that the system has compact structure,adjustable load and excellent low-frequency vibration isolation performance.Firstly,the disc spring structure is introduced,and the stiffness characteristics are analyzed to determine the conditions for its negative stiffness characteristics.At the same time,for the non-standard opening design of the disc spring,the control variable method is used to explore the influence of the opening mode and the central groove position of the disc spring on the static characteristics of the disc spring,and a negative stiffness element with equivalent large deformation and wide negative stiffness range is designed.The results show that the center groove ratio dm1.3 and the single disc spring with inner groove can be used as the negative stiffness unit of quasi zero stiffness shock absorber,and the system has high bearing capacity and wide vibration isolation range.Secondly,the disc spring element with negative stiffness and the cylindrical rubber spring element with positive stiffness are paralleled to form a quasi zero stiffness vibration isolator with a wide range of near zero stiffness displacement.The results show that the system meets the requirements of near zero stiffness,and the influence of center slot size on the vibration isolation performance of the system is studied.The results show that the bearing capacity of the quasi zero stiffness system increases,the quasi zero stiffness range decreases and the low-frequency vibration isolation capacity decreases with the increase of the central slot size.Thirdly,the least square method is used to fit the displacement load curve of the system and establish the vibration equation.The harmonic balance method is used to solve the main resonance response of the quasi zero stiffness system,and the approximate numerical method is used to solve the approximate solution of the up and down jump frequency of the system.The vibration isolation rate curves of nonlinear quasi zero stiffness system and linear spring vibration isolation system are compared and analyzed,and the influence of damping coefficient and excitation force amplitude on the transmission rate of quasi zero stiffness system is discussed.The results show that for the quasi zero stiffness system,increasing the system damping reduces the instability range and weakens the high frequency isolation ability;With the increase of excitation amplitude,the frequency of downward jump incr eases and the vibration isolation interval decreases.Finally,load-bearing adjustable quasi zero stiffness system is designed.The negative stiffness characteristics of the parallel system of the regulating mechanism and the open disc spring negative stiffness mechanism are analyzed,and the coincidence condition between the static equilibrium position of the regulating system and the flattening position of the disc spring negative stiffness is given.It is proved that the quasi zero stiffness system of th e regulating mechanism can meet the low frequency vibration isolation requirements of different loads,expand the bearing range,and avoid the instability of the system such as under load and overload.