Many components for aerospace and automotive industries are currently manufactured using superplastic forming, being the fine-grained aluminum alloy AA5083 widely used for this proposes. However, the development of cavitation voids is inherent in this process and reduces the ductility of the alloy. Back pressure can be used to diminish the growth of cavitation void. The experimental conditions used in this work are in the best condition for nucleation and grow of cavitation, because of the coarse grain size (81 µm), large second phase particles (9 µm) and elevated test temperature (570ºC) in a AA 5083. Domes were formed at 570ºC and at a strain rate of 5x10 -5 s -1 by blow forming with and without back-pressure. They were compared in terms of their final shape, thickness distribution, and quantity of cavitation voids. The effectiveness of the usage of back pressure to reducing the quantity of cavitation void was analyzed.
Superplastic forming (SPF) is a technique that takes advantage of metallic alloys with fine grain size presenting very high ductility and large deformations before rupture under certain conditions. There is a growing interest in this manufacturing process in different areas, such as: aeronautical, automotive and medical, due to the possibility of fabricating complex geometry, lightweight, and strong thin shell parts. The researchers employed an industrial size superplastic hot press and, aiming to start investigations in the field of superplastic forming, finite element simulation and material analysis. This paper presents one of a first works in this field: developing a numerical model and forming a titanium alloy dome. A finite element model was developed to obtain the pressure curve, used as input in the superplastic forming machine control and for thickness prediction. Results and comparisons between the formed part and numerical calculations are presented, as well as the main difficulties the institutions faced in this new research field.
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