A new method for 3D forming of extrusion-based sheets for light-weight hull applications

This paper presents a new, innovative forming method that has been developed for 3D bending of aluminum alloy sheets with integrated T-stiffeners. The main motivation for developing this technology is twofold: (a) reduce construction, operating and service (maintenance) costs while (b) lowering the environmental impact of aspects associated with use and recycling of working boats. Focus is placed on describing the overall system, demonstrating shape flexibility and dimensional capability of components. A prototype forming machine has been built for incremental bending of sheet panels into double curvature part configurations. Full scale forming trials were conducted using friction stir-welded aluminum alloy AA6082 panels with T-stiffeners. The panels were tested in both temper T4 (extruded and stabilized) and temper T6 (artificially aged) in order to determine differences in formability, springback and dimensional accuracy. An analytical method for springback compensation was established using conventional bending theory combined with the deformation theory of plasticity. A comparison between the analytical and experimental results shows that the former demonstrates good capability in predicting springback. The results, as represented by bending–springback diagrams, represent a suitable basis for establishing an automated steering model for forming of 3D geometry configurations based on CAD data received from product designers.