Research On Dynamic Analysis Of Extrusion Ultrasonic Bearing Rotor System

The rotor is the core component of rotating machinery,and the bearing is the most common part of rotating machinery to support and drive.For the modern equipment the relative speed of the rotor is higher and higher,and the gap between the rotor and stator is smaller.So it is of great significance to reduce the system friction between the rotor and the stator.In recent years,as a novel method of restraining vibration,the near-field acoustic levitation effect is widely used,with the use of ultrasonic levitation and ultrasonic reducing friction.It has feasibility for the production of ultrasonic bearing.The research detail contents are as follows:Firstly,a new extrusion ultrasonic bearing is proposed.It is consist of piezoelectric ceramic sheets and a thin walled cylinder which material is aluminum.Six pieces of piezoelectric ceramic sheets which size is 15×5×1 mm are all on the surface of thin wall cylinder evenly with an angle of 120.And they are divided into three groups and connect each other.Compared with the traditional plane or concave ultrasonic bearing,the new extrusion ultrasonic bearing can increase the contact area between shaft and bearing.It also can increase the squeeze film effect and the bearing capacity.So it is worth a further study.Secondly,a modal analysis of the piezoelectric transducer is carried out.When the vibration frequency of the piezoelectric ceramic is the same as the resonant frequency of the cylinder,the resonance will be generated.At this moment,the piezoelectric transducer achieves the optimum operating condition.So,a modal analysis of the piezoelectric transducer is carried out by using the multi-physical coupled fields in ANSYS.The mode of vibration and the resonant frequency of the piezoelectric transducer can be received.The vibration mode of the piezoelectric transducer and the optimum working frequency are ensured.The influence of the base structure size of the thin walled cylinder(include thickness and inside diameter)on the resonant frequency and the vibration mode is studied.The resonant frequency of the piezoelectric transducer is inversely proportional to the size of the inner diameter and proportional to the thickness.This conclusion is reached.So the optimal size of piezoelectric ultrasonic transducer can be determined.Thirdly,the mechanism of ultrasonic levitation was studied.Based on the principle of acoustic radiation,the analytical formula of the ultrasonic levitation gas extrusion film is obtained.Based on the theory of fluid mechanics,the Reynolds equation of the gas squeeze film is derived.Starting from the angle of micro element method,dynamics of viscous fluid continuity equations is simplified to solve by using the method of numerical analysis and the finite difference method,obtaining the ultrasonic gas film force.This paper analyses that the relationship of the ultrasonic bearing force and the levitation gap,ultrasonic amplitude are close when the ultrasonic frequency is sure.So the ultrasonic bearing force is inversely proportional to the levitation gap.The ultrasonic bearing force is proportional to the ultrasonic amplitude when the ultrasonic frequency is sure.Fourthly,the nonlinear dynamic analysis of the extrusion ultrasonic bearing-rotor system is carried out.This paper uses incremental harmonic balance method to analyze the extrusion ultrasonic intermediate bearing-rotor system and the ultrasonic supporting bearing-rotor system.Then it explored the vibration suppression effect of the extrusion ultrasonic bearing-rotor system when the levitation gap and the ultrasonic amplitude are different.So the vibration suppression is inversely proportional to the levitation gap and proportional to the ultrasonic amplitude.Finally,the vibration suppression experiment of the extrusion ultrasonic bearing-rotor system is carried out.According to the theoretical simulation results,the experiment is performed with a single variable principle.And it used eddy current displacement sensor monitoring signal.It used NI collecting rotor vibration signal with two directions.The vibration suppression effect of different suspension gaps and different ultrasonic amplitude on the rotor is studied.The rotor vibration suppression effect is consistent with the theoretical simulation analysis,under different levitation gap and ultrasonic amplitude.