In situ detection of plume particles in intelligent laser welding

Abstract

This study aimed to propose the in situ measurement of particles based on the self-mixing interferometry (SMI) effect for monitoring the dynamic behaviors of the plume. This method was verified through the in situ measurement of tiny moving metal objects. The signal acquisition rate of the method was about 100%. The SMI signal of the detection laser had a waveform similar to the sawtooth waveform, and its intensity positively correlated with the detection laser power density. A focused detection laser was used to accurately measure the sizes of the tiny moving objects at the laser focus position. The measuring range of this method was limited by the half-wavelength and numerical aperture of the detection laser. The distribution of the plume particles with a diameter ranging from 0.3 μm to 4 μm was obtained using the in situ measurement method based on a detection laser with a wavelength of 1.31 μm in the 1-kW fiber laser keyhole welding. By quantitative statistical analysis, the number proportion of particles ranging from 0.3 to 0.65 μm diameter is more than 70% in all the detected particles.