Numerical Analysis And Compensation Research Of Springback In Multipoint Forming For Metal Sheet

Multi-point forming is a flexible manufacturing technology for three-dimensional sheet metal forming. It have applied successfully in many fields, such as the skin of high-speed locomotive,ship shell plates and automobile panel, by right of flexibility on the path, applied extensively, process of automation and other advantages.Multi-point forming mould is composed by a pair of matrices of adjustable punches with the designed tool surface, this forming of technology skillfully integrated with computer technology. On the one hand, Computer in accordance with objective surfaces sculpts the shaping surface, on the other hand, it real-time control of the adjustable discrete elements arranged regularly. In virtue of big advantages of flexible controlling the displacement and speed of elements, multi-point forming processes of different curved surfaces (saddle surface and parabola surface) were simulatedSpringback is an inevitable consequence in the process of sheet metal forming. Due to the existence of springback, it brings great influence for the precision. In this paper, the whole process about how to deal with springback problem is used the finite element software of ANSYS/LS-DYNA. Dynamic-explicit formulation is employed to analyze sheet metal forming processes and the implicit algorithm formulation is used to analyze unloading process. The finite element is applied to simulate the springback processes with different curvature radius and yield strength, the springback and its distribution under different conditions were obtained.In order to effectively reduce the errors of springback, a method is proposed which modified the forming surface of element group in the Multi-point forming (MPF). The procedures are described. By means of modifying the forming surface, the shape of the sheet metal after springback is closer to the object surface. Use of modifying the forming surface (compensation of springback) to improve the precision of forming, it must adjust the height of discrete elements several times, do it like this, sheet metal is not smooth enough. In this paper, B spline curve is used fitting connate into surface to operate the height of the discrete elements which enable the surface smooth. At last, the accuracy of forming was improved after twice compensation of the springback, it was proved that this method can compensate springback of the multi-point forming. These conclusions provide significant reference and guidance to the practical application of multi-point forming technique.