## Electronic Theses and Dissertations

1993

Doctoral Thesis

Ph.D.

#### Department

Mechanical, Automotive, and Materials Engineering

Huynh, V. M.

#### Keywords

Engineering, Mechanical.

#### Rights

info:eu-repo/semantics/openAccess

This dissertation deals with the light scattering from machined periodic surfaces, such as turned surfaces, whose roughness amplitude is greater than the illumination wavelength. The main objective is to establish a theoretical basis for the development of an optical technique for in-process surface roughness measurement. The Beckmann's scalar scattering model was used to determine the scattering patterns for the case where the incident plane was perpendicular to the lay and the case where the incident plane is parallel to the lay. It was obtained that the intensity of any given scattering order oscillated as the incident angle changed. The degree of oscillation was directly related to roughness; as roughness increased the number of oscillations increased. This observation was supported by scattering measurements from flat periodic surfaces. Solutions for the light scattering from cylindrical surfaces were also derived from the flat surface scattering model by using the principle of superposition. A special scattering geometry was considered where the incident plane was restricted to a direction parallel to the lay and near zero grazing angles were utilized. Numerical results were then obtained for different cylindrical surfaces having sinusoidal roughness profiles. These results were later confirmed by scattering measurements from turned surfaces having varied roughness and different materials. In these measurements, it was observed that the surface wavelength was inversely proportional to the fringe spacing. In addition, the location of the first intensity minimum on the central fringe was related to the amplitude of the surface roughness. From these two observations, a new surface roughness measurement technique was developed. This technique makes use of the scattering pattern of the surface to determine both the surface roughness and wavelength. Tested results correlated well with the stylus method. A reasonable accuracy and repeatability were achieved. It was also found that this technique was capable of measuring surface wavelengths from 10 $\mu$m to 300 $\mu$m and surface roughness $(R\sb{c})$ from 1 to 10 $\mu$m. In comparison to other techniques, this method is relatively simple, independent of material property and capable of fast processing speed. In light of these features, it holds great promise for in-process applications.Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .F358. Source: Dissertation Abstracts International, Volume: 54-09, Section: B, page: 4878. Adviser: V. M. Huynh. Thesis (Ph.D.)--University of Windsor (Canada), 1993.