Improvement On The Numerical Simulation Precision Of Completely Penetrated Gtaw Molten Pool Behaviors

To develop numerical models of completely penetrated GTAW molten pool behaviors and to improve their precision of numerical simulation continuously are important research area of the frontiers in welding science and engineering. World-wide researchers have been conducting investigations into this area for many years, and great progresses have been made. However, there are still some important un-solved problems. For example, the previous models have three drawbacks: (1) The calculated rear part of weld pool geometry is not as elongated as the experimental measurement. (2) The employed equations to calculate the weld pool surfaces deformation are not perfect, and the predicted surfaces deformation has a comparatively large error. (3) The models have no functions for predicting or judging the occurrence of collapsing and burn-through defects for completely penetrated weld pool. Thus, deep study paying more attention to the three problems mentioned above, and further improvement on the numerical simulation precision of weld pool behaviors are of great theoretical and practical significances for welding process optimum design and intelligent control.A mathematical model has been developed to simulate completely penetrated GTAW molten pool behaviors, which concerns with various influencing factors in GTAW (such as, moving arc, complete penetration, three-dimensional, transient state, heat transfer, fluid flow, top and bottom surfaces deformation, phase-change latent, and curved boundaries). The model has accounted for the following problems: (1) The effects of moving arc on the distribution of both arc heat flux and arc pressure are taken into consideration and the mathematical expressions of double-elliptic distribution modes for both arc heat flux and arc pressure are given out. (2) The derivation details of weld pool surfaces deformation are introduced under conditions of partial- and complete-penetration, and the perfect extent of the equations for completely-penetrated weld pool surfaces deformation is expounded and proved. (3) The latent heat of phase-change is treated by means of method for the fraction of liquid. (4) The curved boundaries are processed by using the body-fitted coordinate systems, and the governing equations and boundary conditions in body-fitted...