Abstract: Applying highly flexible characteristics of multi-gripper stretch forming machine, the determination of blank shape is based on the target part, according to blank shape grippers clamped, the non-rectangular blank clamping is tested. The finite element models of rectangular blank and trapezoidal blank are built for irregular part, the stretch forming process is simulated, the forming results of two blank are analyzed comparatively. The simulation results show that the stress and strain of trapezoidal blank part is smaller and uniformly distributed; thinning value is smaller than that of rectangular blank part. Stretch forming parts of trapezoidal blank can save materials and improve the utilization of materials. Stretch forming experiments of rectangular blank part and trapezoidal blank part are conducted with multi-gripper stretch forming machine, the simulated results are validated. It has been fully proved that the non-rectangular blank clamping is feasible and the effect of stretch forming is better by numerical simulation and stretch forming experiments, can offer reference and study on stretch forming process of other irregular parts, stretch forming process is expanded in industrial applications, which has laid the foundation for the design and development of new stretch forming machine.

Key words: sheet forming, strain, stress, stretch forming, thinning value