| Summary: | Lasers have been in use to weld materials together for over 30 years, beginning with the ruby lasers. With the recent introduction of compact high average power Nd:YAG lasers with fibre optic delivery, the applications of lasers in welding has considerably increased and is continuing to do so at an expanding rate. A particular example is in the use of fibre optically delivered Nd:YAG laser beams in applications where the flexibility and ease of control of the light beam can be very useful in confined or hazardous areas, for example, inside a nuclear reactor. This thesis has three purposes; firstly, to determine methods through which characterisation of the weld process can be achieved. Two active and three passive systems were designed and built. Of the active systems, it was found that the paramagnetic system was too complicated for accurate use. The laser deflection system required a comparison experiment for interpretation of the weld results, achieved using simulated water "weldpools". The technique gives good information regarding the quality and penetration state of the weld. Of the passive systems, a dual wavelength monitor system and an acoustical monitoring system were built also giving good results regarding weld conditions. Spectroscopic measurements show that plasma conditions in the weld can be neglected to 1 part in 10<SUP>8</SUP>. The second purpose is to use the results from these characterisation techniques to serve as data for a theoretical description of the welding phenomenon and the lack of a plasma serves to make a simple, practical theory possible. Finally, to identify possible systems that can be of use for on-line monitoring and control of a practical laser system for remote welding.
|
|---|
