We present an experimental study of the deep penetration laser welding process which aims to analyze the plasma plume oscillations on a short time scale. Using the high-speed camera we show that the plasma comes out of the keyhole in the form of short bursts rather than the continuous flow. We detect these bursts as the short-time intensity oscillations of light emissions coming from the plasma plume. We determine the period of bursts using the statistical signal processing methods and the short-time frequency analysis. Finally, we compare the characteristics of plasma bursts and the geometry of resulting welds carried out on a 2kW Yb:YAG laser welding machine for the steel workpiece and various welding parameters settings

This paper presents a study of the frequency characteristics of the light emissions in laser beam welding. It is based on short-time frequency analysis of the light intensity oscillations and it results in the identification of the parameter directly correlated to the actual depth of penetration. Applicability of this parameter for characterization of the welds is demonstrated for a variety of welding parameters settings usually used in industrial practice. In addition, the method of short-time frequency analysis is used to detect the eigenfrequencies of keyhole oscillations which are hardly observable by other methods

This paper presents a novel method for optimization and feedback control of laser welding process. It is based on frequency analysis of the light emitted during the process and adaptive shaping of the laser beam achieved by an active optical element. Experimentally observed correlations between the focal properties of the laser beam, the weld depth and the frequency characteristics of the light emissions, which form the basis of the method, are discussed in detail. The functionality and the high efficiency of the method are demonstrated for a variety of welding parameters settings usually used in industrial practice