For modern shipbuilding, line heating is widely employed as an effective method to form complex double-curvature plates, and the shrinkage control method is the key to form the target plate. Taking sail plate forming as an example, heating simulation is realized by thermal elastic-plastic FEM, path planning of sail plate is completed according to the heating line layout of shipyard. Finally, variable shrinkage distribution is realized by loading of different length heating lines which are controlled by the in-plane strain, so as to realize the constant curvature bending deformation of the steel plate under the given shrinkage condition.
In the shipyard, the processing of ship plate depends on the combination of cold processing and hot processing. The typical double-curvature plates include sail plates and saddle plates, and the forming process of sail plates is mainly discussed in this paper. In recent years, the application of induction coil heating in ship plate forming has been widely studied. Hu CC (2017) of Huazhong University of Science and Technology proposed the cold and heat integration automatic line forming machine. First, the main curvature cylindrical plate is formed by concave and convex rollers, and then the target shape plate is formed by hot processing according to the in-plane and out-of-plane strain.
During the hot forming process of the sail plate from the cylindrical plate, the main deformation characteristics are reflected in the shrinkage and the bending degree. The fibers of the slats show different shrinkage at different positions, the maximum shrinkage occurs at the edge of the plate, and the smaller the shrinkage occurs at the center of the plate. In the actual heating line layout, the heating line is usually arranged at the edge of the plate without passing through the center of the plate. The closer the heating line is to the edge, the greater the heat input is, so the shrinkage of the fiber at the edge is larger (UEDA Y, 1994).
