MULTIFREQUENCY FIBER OPTIC SENSORS FOR IN-PROCESS LASER-WELDING QUALITY MONITORING

Laser welding is a high temperature machining process in which there a re two principal methods of beam absorption: absorption by the plasma and Fresnel absorption by the surface. The plasma absorption and rerad iation generates shorter wavelength light waves whereas the heated sur face reradiates in the longer wavelengths. This paper describes the ex perimental relationships between weld quality and the multi-frequency fibre optic sensor signals during laser welding. An analysis of the li kely meaning of the signals is presented together with an appraisal of the technique as an on-line weld monitor.