Metin Ertugrul

Process control at the sealing line during sheet metal hydroforming

Sheet metal hydroforming is a deep drawing process that uses a pressure medium for load transmission. The process is mainly influenced by the control of the blank holder force and the fluid pressure. This report describes investigations of a newly developed process-control system. Process variables can be controlled by the sealing state of the tool. The detection is performed by a CCD-camera system that allows the continuous recording of occurring leakages. Different control strategies can be used to control the multiple process parameters. This paper describes the performance and the limits of the aforementioned technology.

Hydroforming of Laser Welded Sheet Stringers

The hydroforming of sheet metals belongs to deep drawing processes, where the forming capacitiy is performed by a pressure medium. This process is especially suitable for parts with a non-rotationally symmetric geometry. Light-weight structures require particularly weight optimized geometries with a possibility to attach joints or secondary shape elements. Weight and strength optimised structures often use stringer elements to fulfill this requirement. They are used in flat plates or in single curved bodies. The assembling of the sheet stringers is often costly in terms of time and money. Hence, the hydroforming process of those sheet stringers offers a new process chain for the manufacturing of complex, multi-curved hollow parts with pre-attached stiffeners. Thereby, tools and process control strategies are similar to the conventional hydroforming process of blank sheets. This paper describes the hydroforming process of laser welded sheet stringers. It gives a first outline of the potential and the limitations of the new process chain. Blank holder force and the fluid pressure are the main parameters during the hydroforming process.