Structural Design And Vibration Isolation Characteristics Of A Torsional Quasi-zero-stiffness Elastic Vibration Isolator

Shafting vibration widely exists in automobiles,ships,generators,lathes and other mechanical equipment.Generally,conventional vibration isolators can effectively resolve the high-frequency vibration isolation problem,but cannot handle the contradiction between low-frequency vibration isolation and installation stability.Aiming at the low-frequency vibration isolation problem in a shafting system,this paper proposed a simple and compact torsional quasi-zero stiffness(QZS)elastic vibration isolator.The QZS isolator was constructed by combining curved thin-walled beams with slightly bent thin-walled beams.The rated torque was completely supported by the curved thin-walled beams at static equilibrium position.The stiffness of curved thin-walled beams could be neutralized by the slightly bent thin-walled beams,which acted as a negative-stiffness mechanism,leading to high static but low dynamic stiffness characteristics,especially zero stiffness at the equilibrium position.The main contents of this paper are listed as follows:1.The structure of the torsion QZS elastic vibration isolator was designed based on the compliant mechanism design method and the principle of connecting positive and negative stiffness elements in parallel.The static analysis was carried out to determine the geometrical parameters by using ABAQUS,which enabled the quasizero-stiffness characteristic.In order to facilitate the subsequent dynamic analysis,the expression of the restoring torque with respect to the rotational angle was approximated by polynomial fitting.2.Considering the inertia of the rotor and motor in the shafting system,a singledegree-of-freedom nonlinear dynamic model was established,which was solved by the harmonic balance method,and then the torque transmissibility was calculated to evaluate the vibration isolation performance.The finite element model of the QZS isolator was built and the dynamic analysis was conducted by using ABAQUS to validate the theoretical results.In addition,the torque transmissibility of the QZS vibration isolation system was compared with the counterpart linear system,which showed the advantage of the QZS system in low-frequency vibration isolation over the linear system.3.The static experiment on the torsion QZS elastic isolators wad carried out,and the relationship between the restoring torque and the rotation angle was obtained,which presented an obvious quasi-zero-stiffness feature.Furthermore,the dynamic experimental platform was built to measure the dynamic stiffness of the torsion QZS elastic isolator and the relationship between the dynamic stiffness and frequency was obtained.In order to exhibit the advantage of the QZS isolator,the dynamic stiffness of the linear counterpart constructed by removing the lightly bent thin-walled beams(negative-stiffness element)was also tested.The experimental results showed that the QZS isolator notably outperforms the linear one in low-frequency vibration isolation.