Numerical modeling is conducted to analyze a two-step forming process for springback analysis. Inthis process a set of lockbeads in the binder activates just before the end of punch stroke, lockingthe remaining blank in the binder. The continuation of the punch stroke then creates a finalincrement of pure stretch. It is most effective for deep drawings of U-channel type of structuressuch as rails.This technique is also known as "post-stretch" or "shape set" in the automotive industry and in theliterature. Finite element simulations for a straight channel are conducted in order to understand thespringback reduction mechanism of the process and to determine its effectiveness. After anexamination of deformation profile after drawing and wall curl as a result of springback, variousmagnitude of post-stretch amount is modeled and their deformation history is analyzed. It is foundthat a post-stretch strain around 2% almost completely eliminates wall curl. CAE investigationsdemonstrate that the technique is equally applicable to more complex 3D channel, where a stepchannel is examined. The effectiveness of this concept is demonstrated by laboratory experimenton the forming of a U-channel. Various implementation techniques for the process in an industrialenvironment are also suggested, together with a discussion on the associated benefits and costs forproduction use.
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