Hydroforming Of Sheet Metal Pairs From Aluminium Alloys

Novotny, S.; Hein, P.

University of Erlangen-Nuremberg, Germany

Driven by environmental laws and higher energy costs, automobile constructors are working on new concepts for saving weight. Two major strategies are under intensive research: the optimisation of steel constructions as shown in the ULSAB-study on one hand and the auto body construction using aluminum alloys, realized in the Aluminum Space Frame concept on the other hand.
While good material values and the excellent recyclability make sheets from aluminum alloys a good choice material for lightweight constructions, the lower formability compared to steel sheets arises different challenges for part manufacturing.
New production technologies have to be qualified for both, steel and aluminum alloy sheets. The hydroforming of sheet metal pairs, where the pressure builds up between two blanks and forms them into either side of a die cavity, is under research at the chair of production technology. This paper will show the process window, special requirements and potentials of the Hydroforming of Sheet Metal Pairs using sheet material from strain hardening and heat treatable Aluminum alloys.

Process design was done using FE-Simulation tools, and standard material tests like the tension test, LDH-test, bulge test and strip drawing test. The influence of different lubricants and die materials, and the results of forming a part form two aluminum blanks on a hydroforming system will be shown.

A promising approach for the enhancement of the formability of aluminum alloys is forming at elevated temperatures up to the recristallisation temperature, where additional sliding planes are activated in the material. The hydroforming production method offers new possibilities for the realisation of the temperature-guided processing of sheet metals since the pressure fluid can be used for transporting thermal energy into the part. A concept will be shown, how an existing manufacturing system will be enhanced to provide for the thermal options and the other special requirements of this technology

Keywords: Hydroforming, lightweight construction, FE-simulation, process design, elevated temperature