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-s eamed medium-and large-size tubular sections. To optimise the bending capacity of these roller benders, multi-pass applications are generall y utilised. This paper seeks to provide a better understanding of the bending mechanics by proposing a mathematical model for determining th e plate internal bending resistance at the top roll contact for multi- pass four-roll thin-plate bending operations. The model is derived fro m 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 estim ation 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) rela tive to the intended bent plate radius. Theoretical predictions for th e second-and subsequent-pass bending of HP30 aluminium plates are made , these indicating that for bending thin plate the multi-pass four-rol l bending mode is dependent on the bending route.