Development of Thermal Elastic-plastic FEM for Line Heating with Remeshing Technique

Abstract

In order to predict deformation during line heating accurately, thermal elastic-plastic FEM with remeshing technique is developed. The model is represented by a fine mesh near the heat source and much coarser mesh around the fine area. Mesh of the model is updated with the movement of heat source, and solution variables are mapping from the old mesh to the new mesh. The analysis procedure after each remeshing step is the same as conventional method. Results of a typical line heating example show that the remeshing technique ensures the accuracy and accelerates computing speed greatly. Ship hull is formed by many plates with complex geometrical shape which are usually made by skillful workers with line heating. The decrease of these people and lack of new workers specializing in this area will be a problem for shipbuilding. Research on computer aided process dates back to the last decade of 20th century and automation system for line heating has now been employed in some shipbuilding companies. It is recognized to be a much more efficient way compared with that operated by human hand. So it is necessary to predict the distortion quantitatively before performing line heating. Inherent strain method proposed by Ueda and Murakawa is employed currently for analysis of plate distortion under line heating 1) . Stretching strain component and bending strain component are firstly computed based on the initial surface and target surface. And then heating paths can be determined by the distribution of the strain components. Since inherent strain method is an elastic FEM and there are usually some iterative procedures required to obtain the final target shape. Thermal elastic-plastic finite element method (TEP-FEM) is a