Finite Element Method in Assessing Springback of Stamped Parts – A DKT Shell Model 2005-01-0519
Springback is one of the main detrimental factors affecting the dimensional quality of stamped parts in automotive industry. Accurate determination of springback is vital to the design of tools used in the automotive sheet stamping operations. Generally the least distance from a point on a stamped part to the die surface is used as a measurement of the amount of springback. This paper presents a reversed finite element method for assessing the springback of stamped parts. First, the point cloud (coordinate measurement data) scanned from actual stamped parts is triangulated to generate a finite element mesh with triangles. Contrary to the traditional finite element mesh from an existing CAD model, this is a reversed process in which the actual CAD data for the surface is unknown. Then finite element method is utilized to determine the deformation the stamped part needed to conform to the die surface using the minimum amount of work. In this process, only the displacement vector will be refined through optimization, which is also a reversed process. A simple example is used to verify that the nearest point is not the least energy point. Thus, the method presented here is more appropriate for assessing the springback. The proposed methodology is validated using a couple of examples with simple shell sheet. The results show that the numerical scheme is an effective, accurate, and appropriate method for assessing the springback of stamped sheet metals.