Termografia e problemas inversos aplicados na análise térmica do processo de soldagem TIG

Abstract

In this work the TIG welding process of 304 stainless steel was approached numerically. An inverse problem was solved to estimate the heat transfer rate and the thermal efficiency of the welding process based on experimental temperatures measured by a thermographic camera. It was adopted a numerical model to solve the three-dimensional transient heat diffusion equation with phase change and moving source. The model took into account the dependence of thermal properties on the temperature and also the boundary conditions of heat loss by convection. A two-dimensional constant speed moving heat source along the length was considered and its geometry was defined by the gometrial appearance of the weld bead according to experimental data. The golden section method was used to solve the inverse problem in order to minimize a least square error function defined by the difference between experimental and calculated temperatures. The measurement of the experimental temperature by thermography was assomplished by shooting the opposite face of welding sample. The technique requires prior experimental camera calibration and digital correction of thermographic images. The results were compared with experimental data and values obtained by other authors which confirmed the feasibility of the technique in thermal analysis of welding processes.