Blank Optimization For The Sheet Hydroforming Of A Frame-Shaped Structure

Sheet hydroforming is an innovative technology for the production of sheet components with a high strength/weight ratio and is therefore particularly suitable for the automotive industry as an alternative to deep drawing. In the hydroforming process, where there is no solid punch to ensure a uniform material flow from the flange, the blank holder force and the initial blank shape are the only parameters which can influence the contact pressure distribution in the flange and thus the material draw‐in. For this reason the precise definition of the blank shape is crucial for the success of the hydroforming process. In this work an analytical model and the FE‐analysis have been used in the definition of the initial blank contour in case of frame‐shaped structures. First an analytical model, developed for the stretch flanging, was successfully applied to the expansion of the inner hole during the hydroforming of a frame‐shaped part. The model has been then applied to the definition of the initial blank shape for a more complex part and finally refined by FE‐analysis. The optimized blank obtained in this way has been finally used in the hydroforming trials.