| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 97 === In this study, a model suitable for the plasto-hydrodynamic lubrication of cold rolling with the oil-in-water emulsions has been developed. The coupled modified Reynolds and von Karman equations are solved by the Newton-Raphson method. In the numerical simulation, the main factors of influencing the numerical convergence are the initial guess for the inlet film thickness and the inlet speed of strip. The inlet film thickness can be estimated by the Wilson and Walowit formula [5]. The effects of oil volume fraction, surface speed of roller, reduction ratio, forward tension, backward tension, pressure viscosity coefficient, and surface tension group on the lubricating properties of cold rolling are investigated.
Results show that the film thickness increases with increasing surface speed of roller, but its effects on the film pressure, the roll force and the roll torque are not conspicuous. In addition, the film thickness increases as the pressure viscosity coefficient increases. In the condition of the very low pressure viscosity coefficient, hydrodynamic lubrication of cold rolling works by enhancing the forward tension. Ahead of the roll bite, the metal surface has a higher affinity to the oil phase so that water is excluded and the oil pooling is formed because of the difference in the viscosity of the two components of the emulsion. Hence, in the condition of the lower initial oil volume fraction, the thicker film thickness is formed by the higher oil volume fraction in the work zone due to the oil pooling. The oil pooling is mainly influenced by the surface tension group. The surface speed of roller and the reduction ratio could enhance the oil volume fraction ahead of the roll bite.
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