Improvement Of Model And Method For Welding Simulation Calculation Of Large Engineering Components

Welding technology is one of the key technologies in the manufacturing process of many large equipment.In the welding process,the weldments are subjected to local and instantaneous thermal expansion and contraction,consequently have complex deformation and stress.Welding residual stress and deformation seriously affect the reliability and safe service of welded structure.Therefore,it is an urgent problem for enterprises to improve the welding process by accurately predicting the welding deformation and residual stress.At present,the numerical simulation method,utilizing which to predict the welding deformation and residual stress,can meet the demand of practical welding production,due to that this method can not only reduce the blindness of experiment,but also effectively reduces the experimental cost.However,for large complex engineering structures,the present welding numerical simulation method still exists the problems of low computational efficiency,long period and low precision.Based on the above,the present study improves the model and procedure of the existing welding numerical simulation method,and verifies the improved simulation model and procedure on two typical large welding structures of high-speed train roof and large splicing welding pressure vessel.Firstly,a new welding simulation model is established,and is used to calculate the overall deformation of the high-speed train roof after laser-MIG welding.On this basis,the welding sequence of the roof is optimized.Secondly,the welding simulation procedure is improved.For large splicing welded pressure vessels,the distribution of welding deformation and residual stress is calculated by the new simulation procedure to optimize the location and sequence of welding lines.Through improving the model and procedure of the existing welding simulation method,as well as the simulation calculation on the different typical welding structures,the present study provides a basis for further optimization of welding process and in-depth understanding of welding principle.The main contents of the present study are as follows.Firstly,the global existing welding technology and simulation are analyzed,as well as the way to improve the existing welding simulation model and procedure.And two typical weldments are selected to verify the improved welding simulation model and procedure.(Chapters 1 and 2)Secondly,a new welding simulation model is established by improving the two existing models of thermo-elastic-plastic finite element calculation of the local joint and inherent strain of the whole weldment.Specifically for the laser welding and laser-MIG hybrid welding processes,the new welding simulation model is described detailedly.Utilizing the welding of high-speed train roof,the results of experiment and simulation by new model are compared to verify the accuracy of the new hybrid heat source model.Furthermore,the welding sequence is optimized by calculating the overall deformation of the high-speed train roof after laser-MIG welding,so that to provide reference for improving the practical welding process.(Chapter 3)Finally,the existing welding simulation procedure is improved by combining the advantages of thermo-elastic-plastic finite element method and inherent strain method.And the new simulation method is verified by calculating the stress distribution and deformation of pressure vessel when changing the relative positions of its longitudinal seams of the adjacent shell section.Thereupon,the regulation of new simulation procedure is amended according to the calculations.On the basis,the influence of welding sequence on the overall deformation of splice welding tank is explored.(Chapter 4)...