The Relationship betwween Surface Roughness and Film Thickness in Cold Rolling Processes

• Main Authors: Chang bo-gy, 張伯騏
• Other Authors: Hsu,Tze-Chi
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/35512344765478378941

碩士 === 元智大學 === 機械工程研究所 === 86 === In the cold rolling processes ,any of several regimes of lubricants can occur at the tooling-workpiece interface .These regimes can be characterized by the fraction of interface load that is carried by the contact of the roughness peaks or asperities. W.R.D.Wilson has described four main regimes ,thick film ,thin film ,mixed and boundary .The thick film and thin film are often combined and called the full-film regimes .Here there is considerable interaction between the asperities on the roll and billet surfaces, but there is also some hydrodynamic action of the oil. Too thick a lubricant film, like full-film regime will result in a metal surface due to insufficient constraint by the rolls, while too thin a film, like mixed and boundary regimes might allow direct metal-to-metal contact which is responsible for rolls wear, billet surface scoring and other defects. Improvements in quality and productivity in industrial metal rolling require a good understanding of mechanics of this lubrication process. Due to the development of digital computers in the past few years ,the finite element method has been extensively used for metal forming analysis and computer-based simulations has already proven themselves as valuable tools of produce ,process and tooling design . The model combines a rigid-plasticity finite element code with a lubrication analysis. The surface roughness effect on lubricant flow is included by using a average Reynolds equation based on porous medium model and the concept of percolation theory. The simulation of the film thickness are compared with experimental measurements of surface roughness in rolling aluminum A1100 and spcc steel billet with different lubricants ,reductions and rolling speed . The most important thing is to investigate the relationship between surface roughness and film thickness in the four regimes of lubrication .