Numerical Simulation Of Laser Welding Temperature Of Ti₃Al Inter Metallic Compound

When high power laser beam eradiats metal, the interaction between the laser beam and the metal make the metal to melt and to form weld seam, known as the laser welding. Laser welding is a complicated thermodynamic and physicochemical process which involves in material melting evaporating plasma forming and keyhole occurring and so on. These processes produce jointing melting area's temperature field, which affects welding seam shape, joint's microstructures and properties, as well as welding stress and deformation. In order to get high quality welding joint, the laser welding temperature field has to be controlled suitablly. The simulation of laser welding temperature field by computer can help understand it, and build the foundation for the simulation of welding stress, and offer essential reference for welding parameter selecting.Based on soft ANSYS, in which numeral calculation method is employed, this paper developed how to realize the 3D dynamic simulation of laser welding temperature field, and put forward a method about laser welding simulation. During laser welding process part of metal is quickly heated to high temperature and then rapidly cooled. With the laser beam moving, the whole weld'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 typical nonlinear transient beat conduction problem.According to the researcher of laser welding parameter of Ti3Al intermetallics, this paper suggested a welding heat source model of "two points and line", and simulated the laser welding temperature field with this model. The calculation result showed that it accords properly with the trial results.To simulate the laser-welding temperature of Ti3Al inter metallic, the most important problem is that the counting time is too long. There are three reasons as follow:(1) It is difficult to make convergence for solving because of serious nonlinear of material and geometrical.(2) 3D model produce enormous degree of freedom.(3) Simulating have to employ multi-step load for moving heat source.In order to solve problems mentioned above and improve solution accuracy, this paper choused suitable material property parameter, and used transition mesh, with two point and line heat sources model. The program which applyload of moving heat sources and suitable time step was edited by means of ANSYS' APDL (ANSYS Parametric Design Language).This paper also simulates the laser-welding temperature field of titanium alloy. Because of different lattice structure compared with Ti3Al inter metallic, the laser heating effect is different. But when changing the hot efficiency, the simulation results is suitable.Through research and practical verify, the two -point-and-line heat source model and dynamic simulation method on 3D welding temperature field employed by this paper are feasible, which provide theory foundation and instruction, promotes the application of FEM (Finite Element Method) on laser welding temperature analysis and engineering.