Analysis On Gas Squeeze-film Linear Guide Using Ultrasonic Vibration

NFAL(near-field-acoustic-levitation)is a new supporting method based on the gas squeeze film theory, which has significant prospect. However the mechanism of this kind of levitating methods is not clear by now. The characteristic of the squeeze film using ultrasonic excited has been investigated by the analysis and experiment. It is verified that the squeeze film has considerable carrying capacity and could support the objects well.The whole system is made up by the piezo-stack,the horn,the excited plate, the squeeze-film with ultrasonic excited and the specimen suspended. Four coupled fields are involved which include the electrical,solid,fluid,sound. The components of the system coupled each other decide the properties of squeeze-film with ultrasonic excited. Equations including the pressure equation of gas film, the electromechanical coupling equation of the transducer, the vibrating equation of horn and the kinetic equation of free objects have been set up. The proper boundary conditions and initial conditions have been decided. Then the coupled govern equations were solved by the use of software such as ANSYS or MATLAB with value methods. In the numeric calculation, the film thickness is the sum of the defection of excited and exciting plate as well as mean film thickness, so the coupled fields could be calculated.The experimental study consists in two parts. The one is to test and prove the capacity of the squeeze film, the other is to design a linear guide. The experiment of the carrying capacity of the film is used to contrast to the theoretical results. The main contents of the experiment is including the make of the piezo stack and the horn, the selection of the stimulating generator, the displacement sensor, the amplifier as well as the acquisition and process of the signal system. The linear guide is a transport equipment with little or no friction,which could be applied on the field of production. It is proved that the linear guide support on the squeeze-film generated by the piezo ceramics and elastic hinges has considerable load carrying capacity. This study is the explore and practice of the usage of squeeze-film levitation theory.