Springback adjustment for multi-point forming of thick plates in shipbuilding

At most shipyards, flame bending has been widely used to fabricate curved shells. Since residual deformation of flame bending is produced by thermo-elastic–plastic strains, it is difficult to accurately achieve the desired shape. Therefore, mechanical bending processes such as multi-press forming and multi-point press forming have become attractive because such processes can accurately control the desired shape. Springback is one of the major problems associated with mechanical bending. When the pressing tools are removed after the loading stage, the workpiece springs back due to the elastic recovery and the shape deviation needs to be compensated. The tools of the press forming process therefore need to be changed in order for the produced surface to reach the desired shape accurately after springback. Generally, forming tools are designed and constructed to operate through an iterative process in which the die and the pistons are adjusted to compensate for springback after a pressing operation. Such adjustments require significant time and effort. Therefore, the present study investigates not only how to simulate springback deformation, but also the degree of adjustment required to the stroke of pistons in multi-press forming. Finite Element Analysis (FEA) of thick metal forming and an iterative displacement adjustment algorithm are integrated for practical application. Shape deviations between the design surface and the deformed plate are minimized to reach the desired shape.