Enhanced strip-roll coupling concepts for the numerical simulation of flat hot rolling

In the present paper, an enhanced iterative algorithm for the effective numerical simulation of the contact between an elastic roll stack and an elasto-viscoplastic strip or plate in hot rolling is presented. The underlying physical process treated here is the forming of metal within a rolling stand, that is, between a lower and an upper roll set, each of which may consist of one or more rolls. The strip material is described elasto-viscoplastically, whereas the roll stack is deformed elastically. Due to the high nonlinearity of the whole problem, the coupling between roll stack and rolled material is performed iteratively. The contact stress distribution resulting from the strip model describing the material flow bounded by the work rolls serves as input for the determination of the deformed work roll surface, which can be performed very accurately and effectively by applying the analytical and numerical methods outlined in this study. The new deformed work roll contours represent the "flow channel" for the next calculation step of the strip model. The accurate coupling of the strip model with the routines for the elastic roll stack deflection is a precondition to get reliable results concerning profile transfer, incompatible strains, and residual stresses inside the strip, which allows the prediction of flatness defects, such as buckling.