Enhanced mixed lubrication model for cold rolling based on a modular and hierarchical structure
Sprache des Titels:
Tribology in Manufacturing Processes
Conventional cold rolling models commonly assume the validity of Coulomb’s friction law with a constant coefficient of friction along the roll gap. Its value and dependence on rolling speed are determined empirically. In contrast to that, the new mixed lubrication model is based on a physical approach which considers the local variability of the coefficient of friction and allows to evaluate it depending e.g. on the evolution of surface asperities along the roll bite, on the lubricant type and on the local lubricant temperature. This leads to an enhanced modelling of cold rolling with the objective to improve the prediction of the force and power requirements for a wide variety of process parameters and to support the optimization of rolling mills. The overall model exhibits a hierarchical structure and is split into six modules (sub-models). To solve the underlying system of coupled differential and algebraic equations, non-dimensional variables are introduced ensuring a much better conditioned system. These equations are solved simultaneously by applying a damped Newton-Raphson method, which avoids the troubles encountered when using multiple nested shooting procedures as known from literature.