Glass Transitions in Lubricants: Its Relation to Elastohydrodynamic Lubrication (EHD)

The viscosity at the glass transition of a liquid lubricant

“…Glass transition temperatures and pressures [11] and precise viscosity [12] data exist for a liquid lubricant, MCS 460, a cycloaliphatic synthetic hydrocarbon produced by Monsanto. It is one of the model lubricants for which the properties have been tabulated by Hamrock et al [13], although the pressure-viscosity plots in Ref.…”

Elastohydrodynamic Lubrication

“…Two basic concepts that frequently appear in the literature are 'glass transition' and 'limiting shear stress'. The 'glass transition' is a term used to describe a change from the liquid state to an amorphous solid or glassy state under the conditions of extreme pressure and shear rate as found in EHL [63,64]. The effect of pressure is to raise the temperature where the reverse glass transition occurs, i.e., from glassy to liquid state.…”

“…This aspect of lubricant rheology is modelled in the theory of traction by exponential functions to relate viscous stress and shear rate. Glass transition has relatively little influence on EHL film thickness unless it affects the EHL inlet conditions which virtually control the film thickness [63,64].…”

Parallelization and scalability issues of a multilevel elastohydrodynamic lubrication solver

“…where L k is a discrete approximation such as that of Equation (6) to the differential operator L defined by Equation (1). The solution to Equation (14) obtained by an iterative method is denoted byũ k and it approximates the exact solution u with a residual defined by…”

“…This causes the shape of the contacting surfaces to deform and flatten out at the centre of the contact. There are also significant changes in the behaviour of the lubricant in this area; for example, it may take on glass-like properties [1].…”