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A method for modifying the forming tool geometry in order to compensate for springback effects

Anders Jernberg Engineering Research Nordic AB, Linköping, Sweden There is always a certain amount of springback deformation in a metal forming process. The high strength steel is becoming a more attractive choice for many applications when low weight of the structure is of importance. One major drawback with the high strength steel is that the springback deformation increased compared to low strength steel. All currently known techniques to reduce the springback deformation are used in tool design today, so it can be really hard to reduce the springback deformation further. The only possibility to obtain the desired geometry for the sheet after springback is to have a shape of the tool that is different than the desired final shape of the sheet. A method to modify the tool geometry in order to compensate for the springback effect is here presented. It is a heuristic method, based on the difference between the sheet after springback and the desired shape. No parameterisation of the tool geometry is needed. Since no parameters are describing the shape of the tool geometry, it can be modified in an arbitrary way without the restriction of the design space spanned by design parameter. The method is demonstrated on a doubly curved sheet and it is shown that the method gives a very fast convergence for the desired shape of the sheet. It is most likely that the method will work on a variety of different shapes. The method is applicable regardless of the yield strength of the sheet material, but most interesting are probably those materials which gives a large springback deformation, such as high strength steel and aluminium.