Study to define behavior of liquid lubricants in an elastohydrodynamic contact
The spectra of an ester and a saturated hydrocarbon polymer were obtained at pressures ranging from ambient to 2 GN/sq m (20 kilobar) and at temperatures between ambient and 180 C in absorption and between 150 C and 210 C in emission. To simulate contact conditions the fluids were contained in the tiny sample volume of a diamond cell, i.e., the hole in a metal spacer separating two diamonds pressed against each other in a nut crackerlike arrangement. Pressures could be deduced from bandshifts and states of aggregation from bandwidths in the fluorescence spectrum of a ruby crystal immersed in the fluids. An infrared Fourier transform spectrometer was used with attachments specially designed to analyze the radiation passed through the sample and both diamonds (absorption technique) or the radiation emanating from the heated sample and passing through only one diamond (emission technique). The latter technique is applicable to operating EHD contacts. Spectral changes pointing to possible glass transitions and composition changes were observed. Emission and absorption spectra were generally equivalent. Some emission bandshapes appear to be temperature sensitive enough to be useful as internal temperature probes.