Sheet metal bending optimisation using response surface method, numerical simulation and design of experiments

Bending is one of the processes frequently applied during manufacturing of automotive safety parts that are obtained by successive sequences of blanking and bending. This paper describes a 3D finite element model used for the prediction of punch load and the stress distribution during the wiping-die bending process. The numerical simulation has been modelled by means of elastic plastic theory coupled with Lemaitre's damage approach. Numerical simulations were carried out by using the ABAQUS/Standard FE code, for a sufficient number of process parameters combinations, particularly the die radius and the gap between the punch and die. An algorithmic loop, programmed in the Script Language of ABAQUS, was developed in order to investigate the mechanical response of parts bent on a mechanical press for each combination of process parameters. The punch load and stress distribution can be predicted in view of optimising the values of the main parameters involved in the process. Finally, a response surface methodology (RSM) based on design of experiments (DOE) was used in order to minimise the maximum punch load during the bending operation. Numerical results showed the suitability of the proposed model for analysing the bending process. Associated plots are shown to be very efficient for a quick choice of the optimum values of the bending process parameters.