Thrust surfaces lubrication and friction reduction through surface modification
Abstract
Surface pockets have been investigated as a way of enhancing the lubrication condition for a contact operating under heavy loads and/or low sliding speeds (boundary and extreme lubrication regime). The three main purposes of this study were: a) to advance the understanding of the fluid flow phenomenon in a shear driven surface pocket through correlation of observations using micro particle image velocimetry (µPIV) with simulations performed using computational fluid dynamics (CFD) software, b) to investigate the lubrication effects of surface pockets via friction and film thickness measurements and image analysis, c) to examine methods of reducing friction at the interface between two parallel surfaces through the use of surface pockets. Three different test rigs have been developed and used to investigate the influence of surface pockets. The shear driven test rig (SDTR) was designed to simulate cavity flows. It is small and compact, and thus it can be seated on an inverted microscope which was integrated with a µPIV system. A glass disk test rig (GDTR) was developed to investigate shear flow field under load. The GDTR can be used to measure film thickness and friction and record micro videography simultaneously. The µPIV system has also been customized as a portable system which can be mounted on a boom stand microscope for observing flow fields. The axial piston pump test rig (APTR) was developed to study the lubrication effects of surface pockets on the thrust surfaces. A numerical model was built to generate the design curves of pocket geometries and corroborate with the experimental results. Two important lubrication mechanisms of surface pockets have been demonstrated: i) the evidence of surface pockets acting as lubricant reservoirs to supply lubrication under starved conditions and, ii) the application of surface pockets for generating hydrodynamic pressure under fully flooded conditions.
Degree
Ph.D.
Advisors
Sadeghi, Purdue University.
Subject Area
Mechanical engineering
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