In Situ Raman Microspectrometry of Lubricated Tribologic Contacts. Part Two: Simultaneous Measurements of Pressure, Lubricant Film Thickness and Temperature Distributions in a Running EHD Contact

Abstract

Raman micro-spectrometry is used to acquire point spectra in a running EHL contact. The quantitative method developed in part one of this study, measuring the lubricant film thickness, is complemented by a data treatment yielding quantitative values of the pressure and temperature in the lubricant. The comparison between experimentally measured pressure and film thickness distributions and numerical calculations shows an excellent quantitative agreement. The simultaneous quantitative measurement of pressure, film thickness and temperature distribution carried under pure rolling afforded a direct and quantitative correlation between the three parameters.

Investigation of Friction Wear Process in the Presence of Exfoliated Graphite Nanoparticles using Correlative in situ Raman Micro Spectrometry and Post Mortem Raman, Analytical Scanning and Transmission Electron Microscopies

“…The film thickness and pressure distributions (Figure 1A and 1B) acquired using in situ Raman micro spectrometry show that the lubricant film thickness is constant (0.5 μm) in the sliding contact and similar to the film thickness obtained with pure 5P4E (not shown). The pressure distribution presents the classical elliptic shape according to previous numerical simulations [2] the maximal recorded pressure being 0.9 GPa at the center of the contact. As for the thickness, the pressure distribution does not present significant changes compared to pure 5P4E lubrication conditions (not shown).…”

“…The lubrication strategies using solid nanoparticles as antiwear and friction reducer additives developped during the last decades are at the origin of extensive studies [1] in order to understand the action mechanisms of nanoparticles in the friction and wear reduction processes. As far as Raman micro spectrometry is a powerful technique for physical and chemical in situ analyses in a dynamic contact [2], the technique is used, in the present study, to characterize the pressure and lubricant film thickness distributions and to follow the structural evolution of nanoparticles of exfoliated graphite during their transit through the sliding interface. Complementary investigations on the tribofilm generated during friction tests are carried out using post mortem Raman, Analytical Scanning and Transmission Electron Microscopies in order to characterize the composition and the structure of this few nanometers thick surface film.…”

“…In situ Raman experiments are carried out at 25°C on a rotating sphere (saphire) / plane (AISI 52100 steel) tribometer (built at lab.) coupled to the Raman micro-spectrometer (HORIBA HR 800) [2]. Post mortem analyses are carried out on tribofilms produced on reciprocating ball (52100 AISI steel) on plane (52100 AISI steel) tribometer.…”

Influence of the thin-layer sensor connections on the accuracy of temperature measurement in the EHL contact

“…The measurements of temperature in the EHL contact are challenging due to inaccessibility of the contact area and the transient nature of the measured quantity. The optical methods, based either on infrared spectroscopy (IR method) [5][6][7][8] or on the Raman spectroscopy [9,10], and the electrical method, based on a thin-layer sensor, are different approaches that deal with these challenges. In optical methods, one of the mating elements must be transparent for the light used.…”

Total internal reflection Raman spectroscopy of poly(alpha-olefin) oils in a lubricated contact

“…21 Raman spectroscopy has also been used to study lubricant lms in a tribological contact, but in a normal confocal Raman microscope the sensitivity is marginal for studying sub-100 nm thick lms in the EHD regime and inadequate for the study of boundary lubrication. 13,[22][23][24][25][26] The use of a total internal reection geometry in which the Raman signal is generated from an evanescent wave enhances the Raman signal and permits the detection of ultrathin lubricant lms in the contact zone, with a spatial resolution of $10 mm. [27][28][29][30][31] In this paper, we demonstrate the application of TIR Raman spectroscopy for the in situ study of shear thinning in synthetic PAO base oil.…”