Research On The Numerical Simulation Of Fluid Mechanics Equaion In Weld Pools

Numerical simulation of welding process involves mathematics, physics, materials, metallurgy and other disciplines. The weld pool is the most complex and most important part of the welding process. It can be influenced by interaction of temperature, velocity, pressure of fields and other fields. It is extremely difficult to observe fluid flow of the surface and inside in weld pool used by test methods currently. The difficulty is that weld pool is tiny, but the temperature is extremely high, and due to the arc of light interference. While, quantitative results of fluid flow and heat transfer process in weld pool can be provided by numerical method. Therefore, numerical simulation is the very effective tool to study flow and temperature fields in the weld pool.Numerical simulation of TIG (tungsten inert gas arc welding) weld pool involves the coupling between multiple fields and multiple variables. It is a solution problem of non-dependent, nonlinear partial differential equations. Solution region contains two regions of solid and liquid. It is very difficult to determine the boundary conditions. Its numerical calculation not only has the bulky scale, but alse involves many aspects of numerical techniques. Numerical simulation of weld pool not only has important theoretical significance, but also has practical significance.The study includes:Aiming at the coupling problem physical fields of temperature and flow in the TIG (tungsten inert gas arc welding) weld pool, analysing the coupling relationship between variables of temperature, speed, pressure and others in the liquid region and variable of the temperature of the solid region on the weldment. three-dimensional transient control equations, initial conditions and boundary conditions are determined under the certain conditions of strong coupling interaction among above variables. Finite difference method are applied to discretize control equations, in which backward difference scheme is applied to discretize the partial derivatives of time, and six symmetric difference scheme is applied to discretize the partial derivatives of space derivatives, to obtain the discretized equations. And then, Newton iteration method and super-relaxation method are applied to solve these equations. The corresponding solution program is drawn up in Visual Fortran computer language based on the software development platform of MS-Develop Studio. Flow field and temperature field in the TIG weld pool of 0Cr18Ni9 Stainless Sheet can be simulated. Through analysis of simulation results, the correctness of the program can be verified, while rationality and effectiveness of the mathematical model established and the numerical methods adopted in this paper can be also confirmed.