Digital Modeling Of The Dynamic Process Of Welding Pool And The Distribution Of Arc Energy

Welding process was an extremely complex course, which included the physics of welding arc, heat transfer, mass transfer, melt and solidification of metal, etc. The energy distribution of welding arc, fluid flow and heat transfer in the welding pool had great influence on the welding quality. After the mathematical model of welding pool and electric arc were built in scientific method, the flow field and heat field in the welding pool could be quantitatively analyzed, fluid flow and heat transfer in welding pool could be described, the shape and energy distribution of welding arc could also be analyzed. So, it had the practical and theory significance on the implementation of intelligence in welding process.According to the principle of energy conservation, hydromechanics and heat transfer theory, a 3ds unstable state mathematical model for welding pool of GMAW and TIG was established under the kinematical welding arc influence. And finite element method was adopted to treat the model in discretization. The driving force of buoyancy, electromagnetic force, surface tension, droplet impact force etc, were took into account synthetically for built model. Therefore, the influence of heat quantity and momentum, which were introduced into welding pool by droplet, were also considered on thermal cycle in welding process. Meanwhile, there were so many facts considered such as the variation of thermophysical performance parameter with temperature changing, the energy exchange between the welding pool and circumstance, the melt or solidification phase change's influence on the fluid field and temperature field in welding pool.Based on the magnetic hydrodynamics theory, applied fluid dynamics function and Maxwell function, an axisymmetric mathematical model of Ar+N₂ protecting DC TIG was established. The thermal process of welding arc and fluid flow were simulated. The tip cathode was introduced in this study. The physical parameters of Ar and N₂ were non-linear to temperature. Boundary condition was chosen in reason. The hypothesis of current density distribution on the cathode could be avoided when the cathode and arc column were combined together in electrical field calculating. In study by ANSYS, the modular calculation was adopted, the geometrical models such as temperature field, electromagnetic field and flow field were established, the calling results would be iteratively operated.According to the characteristics of the temperature field and flow field in GNAW and TIG welding pool, ANSYS, the software for finite element analysis, was used in this study, the elements were divided with non-uniform grid, the heat absorption of GMAW and TIG welding pool was treated by heat source superposition. Then, all mathematic models were solved. Welding current and speed's influence on the distribution of welding thermal field was studied. Through the experiment of welding technology, comparing the width and depth of welded seam with calculated results of them, it could be concluded that there was little difference between the experimental results and the calculated results from the model.According with the characteristics of the GMAW process, combined the basic theory of intelligent diagnosis, the quality forecasted model of manual neural network was established by using error back propagation arithmetic (BP arithmetic). MATLAB was utilized to study the forecasted model of neural network. In addition, it primarily studied on the feature extraction in the quality intelligent diagnosis process and the calculating method of back ANN model, it also showed the algorithm routine. Then, the quality forecasted model was certificated by the experiment of welding technology. From the test results, both the established model and the adopted method were right and valid.It was measured by raising temperature to the heat power and static performance of Ar+N₂ protecting TIG arc. As the calculated results of welding arc heat power, not only the total welding arc heat power, but also the ratio of the anodic heat power account for the whole welding arc heat power was raised obviously, when N₂ increased. The numerical simulation results of Ar+N₂ protecting DC TIG welding arc was shown that the temperature of welding arc, the current density and the plasma speed were raised when N₂ was increased. It was accord with the higher thermal characteristic of Ar+N₂ protecting welding arc.