Abstract: Based on the surface asperity distribution hypothesis of Christensen and the theory of rolling and hydrodynamics， a mixed lubrication model was set up for cold rolling process in which surface roughness is taken into consideration. The mixed film lubrication constraint relation was also proposed to judge the friction condition. The distribution of film thickness， contact area ratio， pressure stress and friction stress were simulated and analyzed under different conditions using this model. The results showed that larger reduction results in a thinner film thickness， larger contact area ratio of the interface and higher stress. Surface roughness was shown to have a pronounced effect on the contact area ratio and the stress distribution. As the surface roughness increases， the contact area ratio， as well as pressure stress and friction stress， would increase. Higher viscosity lubricant or roll speed can reduce the friction and the rolling force effectively.

Key words: rolling, interfaces, mixed lubrication, contact area ratio, stress analysis