EXPERIMENTAL VERIFICATION AND COMPARISON OF VARIABLE BLANK-HOLDER FORCE TRAJECTORIES PREDICTED USING AN ARMA MODEL

摘要

Variation of blank-holder force (BHF, also known as binder force) in the sheet metal forming process is a well-established method of improving the forming process. Several researchers have demonstrated the advantages of spatial and temporal blank-holder force variation for a variety of part geometries, tooling conditions and material characteristics. Through the use of novel tooling designs like segmented binders, flexible binders and open-loop or closed-loop control, the BHF in a forming process can be varied to produce improved formability, higher accuracy and better part consistency. In previous work, the authors have proposed a novel BHF variation strategy based on the Auto-Regressive Moving-Average (ARMA) model. The strategy is robust and can be applied to a variety of forming situations due to the inherent generic nature of the ARMA model. This paper aims to further validate the proposed BHF strategy through experimental verification and comparison with another BHF trajectory proposed in literature. In the first part of the paper, results for experiments conducted with segmented binders for rectangular pan forming are presented. In the second section, results from the ARMA model are compared to another BHF variation strategy using FEM simulations. The results of the experiments and the FEM simulations demonstrate that the ARMA model can be used to predict an optimal BHF trajectory that gives reduced flange wrinkling, lower strain levels and reduced weld-line movement.