Prediction and analysis of real-time forces in novel 3D flexible rotary stretch forming of complex profiles

Abstract

Three-dimensional (3D), flexible rotary stretch bending is a new forming technology that enables manufacturing complex components, like 3D profiles with varying curvatures, thus addressing several limitations of conventional stretch forming processes. However, little knowledge exists about the force requirements, which in turn influence the design of process and machine tools. In this study, an analytically-based method for effective modeling of real-time forces in 3D rotary stretch bending was developed. This method considers material and geometry parameters, kinematically-controlled loading paths, as well as the workpiece-die friction effect. By forming experiments using aluminum hollow profiles with in-situ strain measurement as well as finite element analysis (FEA), the capability of the analytical model was assessed. The developed method was verified to have a similar capability to FEA for the prediction of real-time stretch strain as well as the forces of profile and tools. Based on the analytics and FEA, the developments of force components of tools during the entire forming process with pre-stretching, stretch-bending and post-stretching stages were discussed, and the friction effect on the forming forces and strain distributions were clarified. The findings facilitate analyzing force requirements and characteristics as well as can support the development of closed-loop control strategies for improved product accuracy.

Prediction and analysis of real-time forces in novel 3D flexible rotary stretch forming of complex profiles