Simulation And Experimental Study On Forming And Welding Of Conical Curved Plates For Ships

The construction process of the hull sections has a very important influence on the construction of the whole ship,and the level of the process largely determines the quality and efficiency of the whole ship.One of the key points in the structure is the sheet forming and joining process,The traditional design process for forming and joining plates relies heavily on experimentation and manual experience,inefficient and costly.The difficult to control spring back during the forming process,residual deformation,and stresses during and after welding,all of which affect the dimensional accuracy and load-bearing capacity of the segmented structure,are all difficult areas of research and are urgent problems to be solved in the ship production process.In view of the above difficulties,the key to the study of the hull tapered curved plate structure in this thesis is the press molding process of the tapered curved plate and the subsequent welding process of the four tapered curved plates.One of the main aspects of the curved plate compression molding process study is to consider two aspects,the conditions for obtaining the amount of plate forming and the avoidance or rational use of post-forming spring back,while for curved plate splicing the key lies in the difficulty of predicting post-weld deformation.Based on the appeal,this thesis uses the finite unit method to numerically simulate the forming and welding of the curved plate compression mould,analyses the key issues in the simulation process and finally determines the forming and welding process of the curved plate compression mold.Firstly,the theory of sheet forming,and the welding process are systematically studied and analyzed to determine the key issues of the forming process rebound and to guide the planning and simulation of the subsequent welding process design.Process planning is then carried out for the compression molding of the conical curved plate to determine the processing details of the forming pattern and the design of the mold.A simulation of the forming process of the tapered curved plate is carried out using the rebound compensation method using finite element software.The degree of curvature compliance and the change in surface thickness after forming are used as characterizing factors to compare the forming quality of the curved plate under different process parameters under pre-planning and to determine the optimum forming process route.Secondly,to address the time and cost issues of the TEP finite element method simulation of a complete tapered curved plate,the TEP finite element simulation of a typical joint based on the TEP method of multi-layer,multi-pass,double-sided welding is proposed.Analysis of its calculation results,temperature field,stress field and overall deformation and in the subsequent design and finite element simulation of the same welding process of the actual trial,selected specific points of residual stress and measurement of the overall post-weld deformation from these two directions for mutual verification,to determine the accuracy and reliability of this typical joint TEP simulation.Finally,for the difficult problem of predicting the post-weld deformation of tapered curved plate butt welds in segmental structures,through the study of the inherent strain method,the inherent strain use method innovation,the previous paper on the typical joint of the thermal-elasticity finite simulation and test research and analysis,the establishment of a new inherent strain method of regional division of data tables,proposed a non-uniform inherent strain method on the hull tapered curved plate structure welding deformation prediction simulation.The subsequent rational planning of the welding sequence for the tapered segments proposes four welding sequences.With the overall deformation as the evaluation criterion,the four welding sequences are optimized by simulation and calculation in order to obtain a better welding sequence.