A dimensional analysis of front-end bending in plate rolling applications

Rolling under asymmetrical conditions such as temperature gradients within the material, difference of the circumferential velocity of the rolls and different friction coefficients cause the rolled slab to bend towards the direction of one of the rolls. This mechanical phenomenon is referred to as ski effect. In general this effect is undesired, since it hinders the further material transport and is a potential danger for the machine components in the proceeding processes. De facto it is possible to exert control on the ski effect in terms of selected peripheral speeds of the rolls. Unfortunately the essential mechanisms and the sensitivity of the influencing parameters in asymmetric rolling are still not comprehended sufficiently. In this contribution a mathematical description of the ski effect is provided, embedding this process into a finite element framework of plasticity in the context of large deformations. In order to qualify the impact of specific process parameters a corresponding dimensional analysis is performed. The introduced dimensionless quantities give rise to a complete parametric study of the process under consideration. Both the ratio of the circumferential velocity of the rolls and the difference of the friction coefficients as a cause for ski effect are exposed and their influence as well as their interdependency subjected to different roll geometries are studied