Evaluation of frequency dependence of adiabatic compressibility and transition of mechanical behaviors for traction oils

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Abstracts of this research results are outlined as follows considering research schedule : (1)Brillouin light scattering measurement technique up to 3 GPa and 150ﾟC was established employing a diamond-anvil cell (DAC). Frequency dispersion of high-presuure density was found out, and it was deduced that, in GHz frequency region, oils behave like elasticplastic at room temperature and transit to viscoelastic and viscous feature with elevating temperature. (2)Around GHz frequency, the dispersion of sound velocity was evaluated by Brillouin scattering. With twice increase of frequency, a few % increase for low viscosity liquids was observed, and 10 % for 10 mPas liquids, and a few % for 1 Pas liquids. Similarly, Dispersion experiment under high pressure was made and physical properties for synthetic lubricants up to 5 GPa were obtained. Dispersion was resulted to disappear immediately with pressure and the possibility of hysteresis of elastic modulus between loading and unloading was proposed. (3)Employing ultra-sonic apparatus, MHz sound velocity measurements gave the value of 1500 m/s independent of the kind of oils and frequency. High temperature measurement system and procedure was established and the preliminary experiment for high pressure ultra-sonic apparatus design was made. (4)The difference of adiabatic compressibility between Brillouin scattering results (GHz) and ultra-sonic results (MHz) was turned out to be at most 40 %. Phase transition of mechanical behavior was estimated up to 2 GPa by extrapolating rheological regime of lubricants proposed by Ohno et al.and high pressure traction test results seemed to be in the elasticplastic region and velocity increase has similar effect as viscosity increase. (5)A new attempt was made, that is, the analysis of frictional force for porous solid materials under very high pressure using DAC,which is similar to lubricants including free volume.