A new approach to the investigation of mixed lubrication in metal strip rolling

Mixed lubrication is an important lubrication mode, and if controlled properly, can improve the performance of metal rolling. However, understanding the mechanisms of mixed lubrication is still a big challenge in the discipline because of the complexity caused by the fluid-solid interaction and random surface asperity deformation in a rolling process. A complete solution to mixed lubrication with full resolution down to the microscopic asperity level is formidable although the fundamental fluid and solid mechanics have been established. A practical approach is to solve the problem in the framework of continuum mechanics with the ingredients of microscopic asperity contacts and the lubricant flow at the interface. This paper aims to take such challenge by establishing an integral approach to reveal the mechanisms of the mixed lubrication in metal strip rolling. This new approach analyses the overall strip deformation with explicit finite element method, but introduces an equivalent interfacial layer to capture the microscopic interface mechanics including the random asperity deformation using a statistical formulation and the effect of lubricant using the modified Reynolds equation. It was found that this approach can effectively predict the contact pressure, shear traction and friction in metal strip rolling processes.