MATHEMATICAL-MODELING OF THE INTERNAL BENDING MOMENT AT THE TOP ROLL CONTACT IN MULTIPASS 4-ROLL THIN-PLATE BENDING

In the roller plate-bending industry, the continuous roller bending of plate is an effective process which produces a wide range of single-seamed medium-and large-size tubular sections. To optimise the bending capacity of these roller benders, multi-pass applications are generally utilised. This paper seeks to provide a better understanding of the bending mechanics by proposing a mathematical model for determining the plate internal bending resistance at the top roll contact for multi-pass four-roll thin-plate bending operations. The model is derived from a consideration of the elastic-elastoplastic deformation through the plate thickness and by separating the incremental elastic and plastic strains in the elastoplastic deformation bands: this enables an estimation to be made of the depth of the plastic deformation, the level of spring-back, and the local bend radius (at the top roll contact) relative to the intended bent plate radius. Theoretical predictions for the second-and subsequent-pass bending of HP30 aluminium plates are made, these indicating that for bending thin plate the multi-pass four-roll bending mode is dependent on the bending route.