| Pneumatic cylinder is widely applied in automatic production as one of common actuating mechanisms in pneumatic system. However, the difference between the dynamic friction force and static friction force is one of the main reasons for the cylinder’s stick-slip motion, affecting process quality, positioning accuracy and limiting the development of pneumatic technology. Recently, as an effective way to reduce the friction, the friction reduction by ultrasonic vibrations has attracted a wide attention. This article will intends to apply the ultrasonic vibration on the rubber strip – steel plate which simulate the internal cylinder piston friction motion pair, and study the theory of friction reduction.The friction in cylinder is mainly affected by the piston sealing parts, by unfolding the cylinder circumferentially along the central axis, the physical model of friction rubber strip- metal plate is established. Comparing the friction between the rigid body and the friction between elastomer and the rigid body, on the basis of full analysis of the existing friction theory, analyzing the applicability of the existing friction theory on elastomer such as rubber. This article use the theory of adhesion and lagging of rubber to build the mathematical model of friction between rubber and steel plate without the ultrasonic vibration about the actual contact area, using the theory of unimodal contact and Hertz contact theory to calculate the actual contact area respectively, to determine the mathematical model of friction about the rubber materials, the diameter of rubber, the strip length of rubber, normal load, roughness. Simplifing the model to analyze the relationship between various influencing factors and friction qualitatively.Analyzing the ultrasonic wave properties by transmission equation of ultrasonic vibration and determining the maximize amplitude of ultrasonic vibration, lay a theoretical foundation to experiment. According to the properties of the ultrasonic wave, using the mechanical action of contact surface and the characteristics of the sliding friction process to analyze the basic principle of ultrasonic anti-friction. Based on our previous study of ultrasonic anti-friction, known as the ultrasonic amplitude is bigger, the friction force is smaller, it is known from analysis that ultrasonic vibration reduced the real contact area so that reducing the friction. Through the relevant research before, this article fits the relationship between ratio of frictional force before and after the ultrasonic vibration and fits the ultrasonic amplitude and ultrasonic voltage linearly related using modal test, and thus established the mathematical model of friction with ultrasonic vibration and ultrasonic amplitude. The relationship between influence factors and the friction are obtained by using the MATLAB numerical simulation according to the model.A friction test-bed is built by using Solidworks software to determinate the components and assembly method, and using ANSYS software to determinate the ultrasonic vibration plate size and transducer parameters with simulation of ultrasonic amplitude. Various influencing factors on the influence of friction in the third chapter was validated by the experiment, and test the anti-friction effect between different rubber – steel plate, which manifest that friction can be maximally reduced to 36.6%. Friction model is built under the conditions of the test-bed Establishing the actual friction empirical correlation by experimental data based on Dimensional analysis, the fit was 99.8%. Compared theoretical analysis of the mathematical model, verified its accuracy, analyzed reasons for the use of the difference. The final analysis, a method of reducing the static friction to avoid creeping phenomenon is improved by a combination of theoretical and experimental approach: reducing the normal load W, reducing rubber diameter D, increasing the mixing elastic modulus E*, reducing the pull tensile strength σmax, increasing the ultrasonic amplitude YA. |
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