Study On The Friction Characteristics Of Pneumatic Cylinder Based On Ultrasonic Vibrations Induced Friction Reduction Theory

As one of the most common actuating mechanisms in pneumatic system, pneumatic cylinder is widely applied in automatic production. However, the friction of the cylinder is one of the main reasons for affecting process quality, positioning accuracy and the life span of equipments. Friction reduction by ultrasonic vibrations is a novel means for reducing friction and has attracted a wide attention and deep investigations in these years. This article will study on the theory of friction reduction by ultrasonic vibrations between rubber and aluminum alloy flat plate and applied it on reducing the cylinder friction in order to improve the static friction characteristics of pneumatic cylinder.This article founded the static friction physical model of flat-flat contacting body couples. The influence of ultrasonic vibrations on the static friction was discussed by derivating the formula of ultrasonic wave transmitting on aluminum alloy plate. Aiming at the friction between piston seal and the inner surface of barrel, a physical model with ultrasonic vibrations is established. The friction reduction mechanism was explained by analyzing the deformation of seal and the contacting states of friction couples.The modes of aluminum alloy flat plate and cylinder were simulated in the presence of ultrasonic vibrations with ANSYS. The particles on aluminum alloy plate and cylinder vibrate in a form of standing wave. Meanwhile, similar to the simulation results of aluminum alloy plate, the maximum amplitude of mechanical wave transmitting on cylinder is nearly the same, with a well-distributed state. Their geometry center is one of the wave loops of standing wave and has the largest vibration amplitude.The test system for the basic investigations of rubber/aluminum friction couple is constructed and the study of static friction and ultimate displacement between rubber and metal in the presence of ultrasonic vibrations are realized. The static friction with vibrations can be reduced to 23.1% of that without vibrations. Moreover, the static friction rises when the normal load increases, no matter whether ultrasonic vibrations are introduced. Increasing the vibration amplitude or the contacting area can both reduce the static friction and ultimate displacement.The test system of ultrasonic vibration induced friction reduction was established. The static friction and ultimate displacement can both be reduced sharply by introducing ultrasonic vibrations on the outside barrel of cylinder. The friction can be reduced to 36.3% of that without vibrations when the cylinder is working on a certain pressure. The ultimate displacement can be reduced to 25%. Increasing the exciting voltage and making the cylinder work at resonant frequency can both improve the static friction characteristics.