Research On Finite Element Analysis Of Welding Process Of Mill Shell Butt Joint

With the development of scientific technology, mathematical model and numerical simulation have become more and more important. Welding is a complicated physicochemical process which involves in electromagnetism, heat transferring, metal melting and freezing, phase-change welding stress and deformation and so on. Once the welding process can be simulated with computer, the best design, procedure method and optimum welding parameters can be obtained. Human resource, material resource and time especially for large complicated weldments can be greatly saved by mumerical simulation. With the development of FEM and computer technology, more and more researchers use numerical simulation technology in welding, and they have got lots of achievements.Dynamic simulation of temperature and stress fields can help to know stress distribution of either position in the welding process, and it also can help to understand the forming reasons of the stresses. The application of such method have a significant meaning in the prediction of residual stresses on weldment. As to the large-scale weldment of slider shoe mill, how to simulate welding prcosess by using numerical technology? It's unpractical to simulate it directly because of high cost, so it needs to be proved by using experimental model which have relation to real model.This dissertation systematically elaborates nonlinear finite element analysis theory in the welding process on the base of the summarization of other peole's work, and uses large general finite elemnt analysis (FEA) software ANSYS to have a analysis of temperature and stress field on butt joint experimental model, the size and distribution of the butt joint is obtained. By comparing the analysis results with spot test, a better coincidence has been achieved. At last, this dissertation also simulates temperature and stress field of the last covering welding of the joint. Therefore, the research work of this dissertation is only an application work, and the main results are as follows:(1) Through to the research of domestic and foreign numerical analysis of welding heat process at present, a suit of methods and experiences have been ascertained to simulate the X bevel butt welding, and a study platform has also been built: firstly, many experience of building calculation mesh, choice of heat resource model, tactics of numerically solving the numerical problem and so on have been accumulated; secondly, the basic theories of non-linear finite element analysis have been better understood and grasped, which lays the theoretical basis for realizing the finite element ananlysis in the welding process.(2) This dissertation plans to systhesize birth-death method and Gauss heat resource to simulate multi-pass welding of the experimental model. By control the death and birth of the element to simulate the course of stuffing, melting, freezing of metal in welding seam. Then, it uses the line-Gauss heat source mode to realize the movement of welding heat source. Thus, the course of heat resource movement can be simulated exactly.(3) Applying the chosen heat source model to the experimental model to have a three-dimensional finite elment analysis of temperature field by using ANSYS software. By comparing the analysis results with spot test, a better coincidence has been achieved. Meanwhile, in the ananlysis, the sampling temperature-time curve of the selected points presents stable state distribution of temperature, thus has proven the reliability and the rationality of the finite element analysis results.(4) After obtaining transient state temperature field, then use the hot-structure indirect coupling method to carry on the finite element analysis and research to the welding heat stress field. The size and distribution rule of the residual stress of the X shape bevel weld joint is obtained by such method.(5) Using blind-hole method to test the surface seam and the near seam area of the butt joint, and the measuring size and rule of the stress consist with the finite element simulation value.(6) The temperature and stress field of the last covering welding of the butt joint have been obtained by finite element method. The relationship that welding straight-seam stresses of the plate are equal to the welding circular-seam stresses have also been established, their forming principle of stresses are also the same. So, when to simulate the welding process of big and thick weldment, plate experimental model is a certain way to research stresses and deformation rule of large-scale weldment in quantity.