Surface roughness formation of tin plates during skin pass rolling with dull work rolls of 165mm and 480mm diameter has been investigated through rolling experiments and elastic-plastic finite-element (FE) analyses considering surface asperity and elastic deformation of the work rolls. Surface roughness predicted by two-dimensional rolling FE analysis exhibits fairly good agreement with experimental results obtained using smaller work rolls of 165mm diameter, but not with results obtained using larger work rolls of 480mm diameter. Discussion has been carried out on the characteristics of surface roughness formation and the validity of the two-dimensional rolling FE analysis in view of the surface roughness of the rolled plates, utilizing three-dimensional die press FE analysis simulating a generic piece of the rolled plate and a unit of asperity of the work roll. It is concluded that surface roughness formation is governed by mean stress in the rolling direction and elongation of the rolled plate, and that two-dimensional rolling FE analysis inevitably induces substantial error in predicting surface roughness for two reasons. One is the neglecting of shear stress acting from adjacent material in the width direction. The other is that, when mean stress in the rolling direction is small, unrealistic nonplastic regions appear in the rolled plate at the concave portion of the work roll. For a practical solution to these problems of the two-dimensional rolling FE analysis, a combination of two-dimensional rolling analysis with three-dimensional die press analysis connected with mean stress in the rolling direction and elongation of the rolled material is proposed for surface roughness prediction.
