High-Pressure Viscoelastic Measurement of Lubricants by Stress Relaxation

Abstract

A new technique to obtain the viscoelastic property of lubricants at high pressure over 2 GPa is proposed. The lubricants tested are BCCM and DMP, which have high viscodity-pressure coefficients. From the difference of the ruby fluorescence wave length between the (0001) and (1120) ruby plate in a diamond-anvil apparatus, shear stress relaxation can be observed. By applying a Maxwell viscoelastic model for the relaxation analysis, an extremely high viscosity ( over lO¹⁵ Pa·s) is obtained and is almost fitted with the extrapolated value of the existing one. Bulk viscosity and elastic modulus are also obtained and are consistent with the existing values.