Study On Several Critical Techniques Of Steel Plate Forming By Line Heating

Line heating is an effective and efficient plate forming method for compound curvaturesurface, which has been widely used in industries of shipyard, automobile, airplane and soforth. Specially, in shipbuilding, the fabrication of shell is still manually operated byexperienced workers. Because of the inefficiency of the manual processing mode, shellforming has become a bottleneck greatly restricting the production of modern shipbuilding.Therefore, it is significant to realize the automation of the line heating process.Line heating is a complicate thermal-mechanical coupling physical process. Firstly, thisthesis presented the overall framework of the study on steel plate forming by line heating, andanalyzed the links between the critical techniques. Then, the basic theories applied in thisthesis were introduced, including DOE (design of experiment), SVR (support vectorregression), surface theory and hybrid PSO-SQP algorithm. The investigations on the threecritical techniques are described as follows:(1) The numerical simulation of line heating process. The line heating process is analysedby finite element method. Besides, the nonlinear material, heat source model and boundaryconditions are discussed. Then, the finite element codes ANSYS is used to finish the three-dimensional transient thermal-mechanical process. The accuracy of this method is proved tobe acceptable by comparing simulation results with experimental results.(2) The prediction of deformation induced by line heating. All potential influences arelisted by fishbone diagram, and fractional factorial design is used to screen the maininfluences. After that, the ε-SVR is introduced to predict the in-plane shrinkage during lineheating process. The model is proved to be effective by comparing the predicting results andexperiment results.(3) The surface development and layout of heating line. The thesis proposed an algorithmof optimal development for doubly curved surface based on surface theory. The surfacedevelopment problem is transformed into constrained nonlinear programming problems,which are solved by hybrid PSO-SQP algorithm to obtain the strain distribution and the initialplanar shape. According to the obtained strain distribution, the layout of heat paths isdetermined.Finally, the above investigations were concluded and evaluated, and the furtherimprovements and refinements of research on line heating were discussed.