This research is an experimental and computational investigation of the thermo-fluid processes associated with fusion welding. The effort is divided into three smaller, clearly focused investigations. The first of these is an experimental simulation of fusion welding, employing a low melting point eutectic. Detailed temperature measurements and surface fluid flow visualizations will be carried out to study the multidimensional, transient transport processes involving phase change. This study will provide a starting point for the subsequent temperature measurements in the gas tungsten arc (GTA) welding process. Thermal histories at various locations during GTA welding will be measured for lead, aluminum and steels. To complement the two experimental studies, computations of heat transfer and fluid flow during fusion welding will also be performed. There are two primary goals of this research. First, a fundamental understanding of the heat transfer and fluid flow processes associated with fusion welding is sought. A number of complex features such as multidimensional convection and conduction transport, change of phase, surface tension and multiple of physical mechanisms which have not previously been considered together in detail. These studies will also provide guidelines to the welding engineer to correlate the thermo-fluid processes with the post weld mechanical properties. In addition, the possibility of providing real time corrective action during welding, using heat and fluid flow measurements will be examined. This will permit real time control of automated welding operations to improve weld quality.
