摘要: The first dissertation investigated the shaping of hot pressed S3N4 with a high power CW C02 laser. The laser was used to heat the surface of a workpiece forming a groove by vaporization. Shaping was accomplished by overlapping th... 展开 The first dissertation investigated the shaping of hot pressed S3N4 with a high power CW C02 laser. The laser was used to heat the surface of a workpiece forming a groove by vaporization. Shaping was accomplished by overlapping the grooves. Results are given showing that groove shapes and material removal rates are independent of irradiation environment. This suggests that decomposition is responsible for the removal of material. An analysis of multiple overlapping grooves indicated, in some cases, that the shape of the overlapped groove differs significantly from that of the single pass groove. To further evaluate the potential of this shaping processs, 4-point bend specimens were tested with laser machined surfaces. In second dissertation, a laser machining proces for shaping non-solid of revolutiuon shapes with a high power carbon dioxide laser operating in pulse mode was studied and developed. Graphite was used as the model material to develop the process and it was demonstrated that the process can successfully be adapted to machine silicon nitride. Materials were removed, a layer at a time and by controlling the boundaries of the layers: a contour shape can be formed. A detail parametric study was conducted to determine the controlling variables in machining grooves and layers. The effects of angle of beam incidence and polarization on groove shape was studied and analysed on the basis of Fresnel's Law of Reflection. Distortion introduced by reflections at the end of a layer was analysed and corrected by reorientation(tilting) of the workpiece with respect to the optical axis of the laser beam. Smoother surface finishes were obtained by defocussing the laser beam so the focal plane was above the workpiece. 收起