Research on quality inspection for backside weld of tailored blank laser welding based on texture feature
In tailored blank laser welding, the quality of backside weld has a significant influence on mechanical properties of tailored blanks. The conventional method for the quality inspection of weld seams is based on the structured light deformation. However, the structured light deformation is not obvious in the backside weld which with dust disturbance, so the extraction of feature points is difficult only based on the structured light. A quality inspection system for backside weld of tailored blank laser welding was built and a new method based on combination of texture feature and structured light was proposed in this paper. In this method, the textural feature of the image was firstly analyzed, and then the image was segmented by the difference of the image texture feature between the weld region and the base metal region; finally, the zone of the weld were recognized based on voting strategy and the feature points were extracted. Experiments were conducted with this method, then the considered weld width was detected and other weld defects could also be detected. The experiment results showed that the proposed inspection system and method were effective for backside weld quality inspection of tailored blanks laser welding.
Tracking and inspection for laser welding
High precision, high productivity and high quality are the three absolute requirements in today's laser welding production. Automated laser welding places extreme demands on tool position accuracy. Accurate real-time tracking and inspection systems for laser materials processing make use of high-performance laser sensors. The reliability of the monitored signal can be significantly increased by using high resolution, digital CMOS sensors and high speed real-time image processing technologies. This paper presents the latest developments in high-performance optical joint tracking systems and optical inspection systems based on these technologies. Optical joint tracking systems allow for precise control of part fit-up, machine self-alignment, and adaptive process control; optical inspection systems allow for automated in-line verification, insuring laser welds meet quality standards and customer's specification. Geometric features of welds can be precisely measured and compared to allowable tolerances while undesirable attributes like surface porosities and external defects can be accurately detected.
Distribution-free monitoring of univariate processes
We consider statistical process control (SPC) of univariate processes when observed data are not normally distributed. Most existing SPC procedures are based on the normality assumption. In the literature, it has been demonstrated that their performance is unreliable in cases when they are used for monitoring non-normal processes. To overcome this limitation, we propose two SPC control charts for applications when the process data are not normal, and compare them with the traditional CUSUM chart and two recent distribution-free control charts. Some empirical guidelines are provided for practitioners to choose a proper control chart for a specific application with non-normal data.