Characteristic Analysis Of A New Kind Of Quasi-zero-stiffness Vibration Isolator Under The Variable Load

With the rapid development of technology,people's requirements for accuracy in industrial production are more stringent.The existence of vibration greatly affects the accuracy in high precision machining.Therefore,vibration control,especially for the isolation of low-frequency,has very important significance.Aiming at low-frequency vibration control,in this paper,a quasi-zero-stiffness isolation system with positive and negative stiffness in parallel is designed,and the compliant mechanism is introduced to satisfy the variable load working condition.The system has high static stiffness and low dynamic stiffness so that it has good low-frequency vibration isolation performance on the basis of its bearing capacity.According to the principle of the quasi-zero-stiffness and the finite element analysis software ANSYS,a positive stiffness element air spring is designed.The static mechanical properties of the structure under different initial conditions are calculated and analyzed.Combined with the positive stiffness curve,a negative stiffness element Euler buckled beam with axial load is designed.And the load-displacement relationship and the stiffness curve are calculated under different prestress conditions.What's more,to satisfy the variable load working condition,the compliant mechanism is introduced to transfer the load to negative stiffness element,and therefore it can apply the corresponding axial force and vertical displacement to produce the negative stiffness suitable for the current load,so as to satisfy the quasi-zero-stiffness under varying load condition.By the parallel of positive and negative stiffness elements,the two quasi-zero-stiffness isolation system with and without compliant mechanism are designed.The ANSYS is used to analyze the static mechanical characteristics of the two quasi-zero-stiffness system before and after the introducing of compliant mechanism.By comparing dynamic stiffness values of the two systems under different load conditions,the results show that by applying different initial internal pressures,the dynamic stiffness of the system with compliant mechanism can be at a small dynamic stiffness within the load range of 1100kg~1800kg,and the condition of low-frequency vibration isolation is realized.Based on the harmonic balance method,a quasi-zero-stiffness system dynamic equation is established,and the amplitude frequency response curve is obtained.The influence of the damping ratio,stiffness and excitation amplitude on the dynamic characteristics of the system is studied.By using the finite software,the low order mode of the system with compliant mechanism are calculated,and the harmonicresponse analysis at different frequency ranges is studied.Compare the results with the harmonic balance method results,thus the good vibration isolation effect of the system in the low-frequency vibration range is verified.