A THREE-DIMENSIONAL MODELING OF THE THERMAL FIELD DURING WELDING THERMAL CYCLE

Abstract

In this paper finite element modeling of welding thermal cycle is studied. The finite element method (FEM) is the dominant discretization technique in structural mechanics. FEM simulations are nowadays useful to predict such things as the weld pool shape for various combinations of process parameters from the temperature distribution plots. One of the important problems in welding engineering is to construct a mathematical model for the computer simulation of welding process. During the welding process, because of the heat input transferred to the material, heat transmission inside the work-piece and heat exchange with the external environment occur. Numerical simulation of heat manufacturing processes is preferred to analytical methods for modeling in welding technology. In fact as the welding arc interacts with the surface of the work-piece during its passage, very rapid series of heating and cooling cycles are achieved. Therefore it results to be difficult to adopt analytical model technique to investigate about the process. Instead numerical models are suitable to assess the thermal cycles and their relationship with process parameters. Welding was done with different modes to analyze and predict the geometry, the shape of the seam and the depth of weld penetration. For the calculation of the thermal conditions accompanying the process of melting the metal surface, a mathematical model was used, which is based on the differential equation of heat conduction in a three-dimensional Cartesian coordinate system. In this work the simulation of the thermal field during the TIG welding process of VT23 titanium alloy joint is presented. The thermal analysis is concentrated on the prediction of the heat transfer in the weld. A distributed volume heat-source was validated on the basis of the comparison with the experimental specimen cross section. The temperature distribution in the overall weldment, the shape and size of the fusion zone, heat affected zone, the maximum cooling speeds in different parts of HAZ were predicted. Based on quite satisfactory results, this work shows, that FE simulations can enable faster, less costly, and more optimized product development, as well as examinations of product performance that would not be possible even using very detailed prototypes.