The automobile industry has defined the quality of a lap weld by the width of the weld bead nugget at the interface. A suitable technique for on-line, non-destructive monitoring of interfacial width during welding is of great interest to manufacturing industry for scrap and cost reduction.
This paper describes a technique which may potentially be applied in industry for prompt results. The strategy of this technique involves visualization of the surface melt pool dimension and development of correlation between the surface melt pool dimension with the interface width using a three-dimensional mathematical model. Unfortunately, the laser weld pool is always shrouded under an intense plasma column. Therefore, for visualization, weld pool was simultaneously illuminated with focused and diffused Nd-YAG laser light and the reflected light is collected by a CCD video-camera with narrow bandpass filter at 1.06 μm wavelength.
Pool width is compared to the width of the solidified laser weld at the interface through a cross-section analysis. Experimental results are compared with theoretical calculations for this experiment. A correlation between visualized surface pool width and anticipated interfacial bead width is then developed.