Tensile strains ahead of entry into the roll gap

Tensile strains ahead of entry into the roll gap were analysed using the finite element method and compared with results of the analytical approach developed by Pawelski [1]. The longitudinal tensile strains in the stock surface ahead of contact with the roll produced by frictional contact with the roll were calculated for the different roll gap aspect ratios, h(o)/L = 0.1,... 1 and Coulombic friction coefficient 0. 1,... 0.5. The results have been analysed in terms of oxide failure resulting from this kind of deformation and compared with predictions using the advanced oxide scale model. A simple formula has been developed to evaluate the longitudinal strain component at entry into the roll gap for a given friction coefficient and aspect ratio. It was related to cracking of the oxide scale in tension at this area. Prediction of the scale behaviour at this area is a key to understanding the friction and heat transfer phenomena taking place at the roll/stock interface. It is also important for optimisation of descaling operations.