Press bending and line heating are two forming methods to shape the curved hull plates in shipbuilding industries. There have been many attempts to automate the forming process, but no feasible solutions are seen due to lack of information required for the automated process. In this paper, first the kinematics of final curved shells with reference to the flat plates is studied. Second, a numerical modeling of the thermo-elastic-plastic analysis of the line heating is suggested for double curvature shells. These combined information helps establish an automated process of forming curved shells.
Ship hull plates at fore- and after- body have double curvature. Ship hull plate parts are traditionally formed up to the required double curved shape through the process of shell development, press bending and line heating. Two types of research on the plate forming process have been in-progress. One is how to get the desired surface, and the other is how much the deformation of a plate by the heat source is. The studies on how to get the desired surface is to determine the heating path, heat energy, and the processing sequences. Ueda et al (1994a) divided the deformation caused by line heating as bending strain and in-plane strain, and investigated the effect of each component. For the studies to get the deformation of a plate by the heat source, strip model was given by Moshaiov and Shin (1991). Kawakami et al (1985), Shin et al (1995) has modelled the line-heating process by using a general finite element analysis package. But, up to present, the studies overlooked the shell development process of the desired surface into the flat plate. Because the hull plate forming is the reversal of the shell development, plate forming and shell development process must be studied concurrently. Therefore this paper presents how to estimate the inherent strain by mapping between the shell surface and the developed plate.