Correlation between the Keyhole Depth and the Frequency Characteristics of Light Emissions in Laser Welding

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.