As ship frame, the asymmetric section-angle section need to be bent to particular shape. However there are side bending deformation in bending process which is deformation generated in the vertical direction during the angle section subjected to horizontal bending due to asymmetric section. In order to eliminate the deformation in the vertical direction, a vertical pre-bending method is presented to obtain flat bending parts for three-point bending. Numerical simulation of web-out bending process of the angle section are performed by Ansys LS/DYNA software. Angle section L100×63×8 bending test is carried out to verify the validity of the finite element analysis.
The profiles and the plates are welded together to form the whole hull. In order to reduce the ship resistance, the ship is designed to streamline at the bow and stern. Therefore, the profiles and plates are required to bent to desired shape. The three kinds of sections, angle section, bulb section, and T section are mainly used as profiles for ship structure. In addition to the T section, angle section and bulb section are asymmetric profiles.
For the aviation or mobile industry, the profile is forming by the fixed mould. But the ship is different, which belonging to the order type products. It has a variety of products and a small number, even single one, and the size of the section used is relatively large. So it is impossible to use the fixed mould processing. In order to form the desired shape, the shipyard generally uses frame cold bending machine to forming profiles by three point bending.
It was found that the vertical deformation of web plate comes into being along with horizontal bending for asymmetric section. This phenomenon for the sagging or hogging of web plate is called as side bending or lateral bending. Because the web edge of the section is welded in shipbuilding, it should be flat in a plane, so this defect must be overcome or corrected.