STOCHASTIC-MODEL OF THE DEEP PENETRATION LASER-WELDING OF METALS

Deep penetration laser welding of metals generates a keyhole surrounde d by a molten region which forms the weld on freezing. Mathematical mo dels of the process produce relationships between the process paramete rs to provide an effective simulation of the process and a guide to op timal operating conditions both for continuous wave (cw) and pulsed sy stems. It is usual when pursuing such an analysis to assume the existe nce of a suitably averaged keyhole structure. To assume a steady-state keyhole with suitably averaged properties, however, constitutes a con siderable idealization. Actually, the keyhole manifests itself as a wr ithing, twisting entity. This characteristic arises from many differen t instabilities that can and do inevitably come into play. They repres ent the reaction of the material being welded to the laser beam. It is even more necessary to consider such reactions to the laser beam when pulsed lasers or cw lasers with pulsed modulation are considered. The details concerning the characteristics of specific instabilities are not considered here. Instead, a stochastic description of some aspects of the laser welding process is provided when the laser operates in t he cw case. The applicability of current mathematical models is thus e xtended giving increased insight into the nature of the laser welding process. (C) 1998 Laser Institute of America.