Visualization and acoustic monitoring of laser weld pool oscillatory behavior

Abstract

The physical phenomena which govern the laser beam-material interactions involved in welding give rise to a variety of thermal, optical, and acoustic signals which are potential sources of process diagnostic information. A number of sensors are available to monitor these signals and provide information regarding laser weld quality (e.g. weld pool geometry and the presence of discontinuities). The objective of this study is to examine one potential source of process diagnostic information—oscillations of the molten weld pool—using both acoustic signals and visualization. Oscillations are triggered during the welding process by a variety of disturbances including mechanical vibrations, escaping gases, and sudden changes in laser power. The resulting oscillations can provide information about weld pool geometry. Oscillations are monitored optically using a high-speed camera, and oscillatory frequencies and mode shapes are identified. Analyses are conducted to determine if weld pool oscillatory motion can be detected acoustically. Acoustic pressure variation as a function of distance from the weld pool and angular location about the pool are calculated.The physical phenomena which govern the laser beam-material interactions involved in welding give rise to a variety of thermal, optical, and acoustic signals which are potential sources of process diagnostic information. A number of sensors are available to monitor these signals and provide information regarding laser weld quality (e.g. weld pool geometry and the presence of discontinuities). The objective of this study is to examine one potential source of process diagnostic information—oscillations of the molten weld pool—using both acoustic signals and visualization. Oscillations are triggered during the welding process by a variety of disturbances including mechanical vibrations, escaping gases, and sudden changes in laser power. The resulting oscillations can provide information about weld pool geometry. Oscillations are monitored optically using a high-speed camera, and oscillatory frequencies and mode shapes are identified. Analyses are conducted to determine if weld pool oscillatory motion can be ...