Rib-Structures on A5083 Aluminum Alloy Sheet Generated by Friction Stir Forming

Abstract

Abstract Reinforcing a plate with a rib structure to increase the moment of inertia of its cross-sectional area is a common technique for the design of lightweight parts. However, this technique is not as popular for sheet-metal forming as for die-casting and injection molding because there is no effective industrial way to generate ribs for sheet-metal forming. This paper describes a new forming technology, friction-stir forming (FSF), to generate a rib structure on an aluminum alloy plate. The proposed process is as follows. The authors put a 3mm-thick A5083 aluminum alloy plate on a die and conducted friction stirring on its back surface. The material deformed and precisely filled grooves of the die due to high pressure and heat caused by friction stirring, to form a rib structure. This study investigates the forming conditions and the corresponding results, including the height limit of the rib structure. Results indicated that ribs even less than 1mm thick were successfully generated. For example, the maximum height of a 0.8mm-thick rib was 2.98mm with the offset pass. Greater groove width of the die resulted in higher rib generation. However, the height decreased for grooves wider than 2mm because of limitations of the deformable material volume. In the experiments, the maximum moment of inertia was obtained when a 3mm-thick, 4.29mm-high rib was fabricated. The moment of inertia was calculated as 7.1 times that of the original plate, provided that the ribs were fabricated at intervals of 10mm.