Development of a Heat Input Model for Friction Stir Welding

For decades, models have been developed for predicting the size of the weld nugget and heat affected zones in fusion welding processes. The basis for these models is the welding heat input, which is fairly well understood for most arc welding processes. However, this traditional approach is not as straight forward in Friction Stir Welding (FSW) which has proven to be an effective process for joining aluminum and other materials. During the past decade, some investigators have proposed that heat input in FSW is proportional to rotational speed and the travel speed. Others have suggested that it is related to the square of the rotational speed. To date, there is no definitive relationship to quantify the heat input for FSW. It is essential that these relationships be characterize such that a process efficiency and heat input can be established. A fundamental study was undertaken to determine essential process variables and their relationship to process heat input. Initial investigations indicate that spindle speed, travel speed and depth of tool are the most important factors contributing to heat input. Detailed results of this study will be described.