Modelling the forming zone of force fitted bending processes

Abstract

Increasing the flexibility of manufacturing processes is regarded as key challenge for modern production facilities to meet the requirements of market economy. An option to achieve a wide production variety of forming processes is to realize geometrical independence between tools and products. If not bound to tool shape, force transmission from machine to product can be transposed by friction. Because strain is determined by the size and shape of the forming zone, it is hence of crucial interest how the zone develops over the ongoing process. This study presents an analytical approach to study the forming zone of a frictionally engaged, i.e. force fitted, bending process. The model depends parametrically on the mechanical material properties as well as the kinematic parameters with regard to bending angle, clamping pressure and friction. An estimation of the material portion, that is drawn out of the initially clamped area is given by the analytic process model which can thus be deployed to describe strain within the bent arc. For validation purposes, the force fitted in-plane bending process is implemented in a numerical simulation based on solid elements. A significant influence of the material’s hardening properties on the forming zone is observed from the models. With regard to the process, the parameters clamping force and friction coefficient were identified as important influences. With these achievements, the present approach is intended to deliver transferrable knowledge for forming processes, in particular about the areas where tool clamping applies, and thus the impact of strain on geometry, such as the beginning and ending transition zones of a bent arc. In contrast to numerical approaches, the presented analytical model does not require significant computing effort and, with regard to its equations, allows to identify the main influences on strain generated within the forming zone of force fitted bending.