Numerical Simulation Research On Welding Stress And Deformation

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. In order to get high quality welding structure, we have to control these factors. If welding process can be simulated with computer, we will easily determine the best design, procedure method and optimum welding parameter. Based on summing up others' experience, employing numerical calculation method, this paper researches how to realize the 3D dynamic simulation of welding temperature field, stress field and welding deformation when weldment is been welding and welding residual stress and residual deformation when weldment is cooled, then uses the research result to simulate the welding process of board surfacing. At the same time, the calculation result accords with traditional analysis results and theory results.Welding process is that parts of an area is quickly heated to high temperature and then rapidly cooled. With the heat source moving, the whole weldment's temperature sharply changes, and the material's physical property parameters also sharply change. At the same time, there is latent heat of melt and phase-change. Therefore, the analysis of welding temperature field is a typical nonlinear transient heat conduction problem. Because of non-uniform temperature distribution, at the course of welding and postweld, weldment takes on serious welding stress and deformation. Calculation of welding stress and deformation includes geometrical nonlinear problem and material nonlinear problem.Although welding temperature field and stress, strain field are bi-directional couple, because stress and strain field have little influence on temperature field, this paper only considers the single couple which temperature field effects on stress and strain field. When calculating, through ANSYS' thermal-structure couple function, firstly calculate welding temperature field and save the result, then use the temperature result as load to calculate weldingstress and deformation.The most important problem, we have to face when calculating, is that the counting time is too long. There are three reasons:(1) Serious material and geometrical nonlinear result in difficult solving convergence.(2) 3D model has enormous degree of freedom.(3) Have to employ multi-step load for moving heat source.In order to solve the problem and improve solution accuracy, this paper chooses suitable material property parameter, uses transition mesh, chooses Gauss function heat source model, uses ANSYS' APDL (ANSYS Parametric Design Language) to compile program to apply load of moving heat source, chooses suitable time step, uses the method of "birth and death" method to simulate the weld pool's melting and freezing.Through research and practical verify, this paper establishes a feasible dynamic simulation method on 3D welding temperature field, stress and deformation, which provides theory foundation and instruction, promotes the application of FEM (Finite Element Method) on welding mechanics analysis and engineering.