Laser-Vision-Based Measurement and Analysis of Weld Pool Oscillation Frequency in GTAW-P

An innovative laser-vision-based sensing method is proposed to measure weld pool oscillation frequency in pulsed gas tungsten arc welding (GTAW-P). A low-power five-line laser pattern is projected onto the entire weld pool surface as well as its reflection is intercepted by an imaging plane and captured by a high-speed camera. By observing and analyzing the change of the captured laser images during the base current period, it is found that the variation of reflected laser lines is periodic and has a strong relationship with the weld pool oscillation. A novel image processing algorithm is also developed for extracting the pool oscillation frequency. Several experiments with varying weld joint penetration for traveling and stationary weld pools were conducted, and the oscillation frequency extracted. Experimental results show that the weld pool oscillation is capable of being observed by this method. The extracted frequencies were verified, and the oscillation frequency of partial penetration is higher than the complete joint penetration, along with an abrupt transition. The image processing method and algorithm demonstrated good robustness and effectiveness, and could be used to monitor and control weld joint penetration in real time.