Optical Elastohydrodynamics

Abstract

In Part 1 an extended series of pictures are given showing the shape of a point elastohydrodynamic contact. Extremely good fringe visibility is obtained by taking account of the reflectivity of the semi-reflecting chromium layer on the glass plate and the reflectivity of the steel balls. The shape of the contact is quite different from the Hertzian shape frequently assumed. Figures are given for pure rolling, pure sliding and skewed contact giving a slide/roll ratio of 016. Careful collimation permits the 30th fringe order to be observed. In Part 2 detailed design considerations needed to give sharp single and multiple beam interference pictures are studied. Subjects considered are the qualities of the rolling pair, the degree of collimation and the design of collimators. The choice of reflecting layer and light sources is discussed. Methods of estimating phase change on reflection are described. A technique making possible film thicknesses down to 100 Å (0.4 μin) is given.