Degree Name

Doctor of Philosophy


Department of Materials Engineering


This thesis presents a comparative study of single- and tandem-beam welding with a pulsed Nd:YAG laser. When two beams from the same laser are used in tandem to weld a material, it is the intensity distribution of the composite processing beam which is important. This is similar to being able to select the mode of the laser beam, as the relative intensities, spacing and spot sizes of the two beams can be varied. The potential benefits of such a scheme over single-beam laser processing were determined to be the removal of potential contaminants to the weld with a minor beam ahead of the main welding beam; the abiUty to control the heating and cooling rates of the workpiece by employing a minor beam to effectively pre-heat or post-heat the weld; an improvement in the microstructure and formability of the steel welds examined in this study; and the modification of the penetration characteristics of single-beam laser welding with the same total power.