Numerical simulation research on the loading trajectory in stretch forming process based on distributed displacement loading

Abstract

The stretch forming process based on distributed displacement loading presents a better ability to form three-dimensional surface parts, because the stretch forming load is applied by displacement at a series of discrete points and the loading trajectory can be individually controlled at each discrete point. To investigate the influence of the loading trajectory on the forming results, four different loading trajectories were designed and the corresponding forming processes were numerical analyzed. It was found that the loading trajectory can greatly change the values and distributions of the strain and the stress on the formed surface, the optimal loading trajectory among the four trajectories is the one whose material elongations and rotational angles of clamps vary according to cubic functions, the stress and strain in the forming process with this loading trajectory are the smallest, and the deformation distribution of the sheet metal on the formed surface is most uniform. Numerical results shows that the mean and the range of stress of the spherical part formed with optimal loading trajectory can be reduced by 26 and 44 %, respectively, compared with those of the part formed with traditional loading mode. Through the numerical analyses on the stretch forming processes with different number of loading points, it was concluded that the more discrete loading points are, the more uniformly the longitudinal strain distributes on the formed surface of sheet metal and the smaller the mean strain value will be. Experiments were carried out, and the results show that the three-dimensional sheet metal parts with good quality can be obtained by the stretch forming process.