Investigation of tension force in stretch forming of doubly curved aluminum alloy (Al5083) sheet

Aluminum alloys, which are suitable for lightweight applications, are being applied widely in diverse industries, especially to the external bodies of automobiles, ships, and aircraft. The external bodies of these vehicles have a three-dimensional geometric shape with various double curvatures. However, aluminum sheets with double curvatures are difficult to form because of their elastic recovery characteristic, known as the springback effect. As a consequence, the stretch-forming process is widely used to reduce the springback phenomenon and to obtain the desired quality product. In the stretch-forming process for aluminum sheets, the stretching conditions should be precisely designed to achieve high accuracy and minimum product defects. In particular, thickness reduction and elastic recovery of the formed plate must be considered during the determination of the stretching force. In this study, the deformation of an aluminum plate according to the magnitude of a tension force was analyzed and an optimal tension force proposed, while considering changes in the mechanical properties of the formed material. FE simulations and experiments show that the proposed tension force can be used to manufacture doubly curved aluminum surfaces with minimum thickness reduction and high accuracy