Date of Award
Master of Engineering Science
Mechanical and Materials Engineering
Dr. George K. Knopf
Dr. Evgueni Bordatchev
Laser micro-polishing (LpP) is a new surface finishing technology to polish free-form micro-structured components. Unlike conventional chemical or mechanical material removal polishing process, the new LpP approach polishes a surface through melting and redistributing a thin layer of molten material. As the molten material relocates from the local peak towards the local valley due to surface tension, an ultra-smooth surface is achieved. However, the melting and the flow of molten material is a complex thermo-dynamic process, where the initial surface micro-geometries could largely influence the outcome of the LpP process. Therefore an experimental and statistical approach was applied in this thesis to investigate the polishing characteristics of the process, and to investigate the significance of the initial surface micro-geometries in LpP.
Surface geometries were treated as spatial randomized processes in the analysis. Through comparing the surface statistical organization before and after polishing, the LpP process was confirmed to achieve a smoothen surface through redistributing high spatial frequency components into the lower spatial frequency domain. However, the amplitude gain in the lower spatial frequency could be countering the polishing effect, and could hereby define a surface geometry limitation to which LpP could apply. The Lju.P performed in this thesis had a Gaussian profiled laser beam and was found to have two operating regime: a bulge formation polishing regime and a shallow molten polishing regime. Both regimes had its pros and cons, and different polishing strategies were to apply in polishing different surface geometries. However, in polishing a micro-milled AISI HI3 tool steel, the LpP process was found limited to polish surface geometries having roughness greater then 300nm Ra, or it would elsewise damage and worsen the surface geometry if a smother surface was applied. On a continuous wave laser polished surface, however, a surface roughness of 72nm Rawas archived on AISI H I3 tool steel.
Chow, Michael Tze-Chun, "IMPACT OF INITIAL MICRO-GEOMETRY AND PROCESS PARAMETERS ON THE FINAL ROUGHNESS OF LASER MICRO-POLISHED SURFACES" (2011). Digitized Theses. 3403.