Boundary film shear elastic modulus effect in hydrodynamic contact. Part II: influence of operational parameters |
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Authors: | Yongbin Zhang |
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Institution: | (1) Zhejiang Jinlei Electronic and Mechanical Co. Ltd, Hangzhou, Zhejiang, People’s Republic of China |
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Abstract: | The present paper is the subsequent research of the first part (Theor Comput Fluid Dyn, 2009). It investigates the boundary
film shear elastic modulus effect in a hydrodynamic contact in different operating conditions. The hydrodynamic contact is
one-dimensional, composed of two parallel plane surfaces, which are respectively rough rigid with rectangular micro projections
in profile periodically distributed on the surface and ideally smooth rigid. The whole contact consists of cavitated area
and hydrodynamic area. The hydrodynamic area consists of many micro Raleigh bearings which are discontinuously and periodically
distributed in the contact. The hydrodynamic contact in a micro Raleigh bearing consists of boundary film area and fluid film
area which, respectively, occur in the outlet and inlet zones. In boundary film area, the film slips at the upper contact
surface due to the limited shear stress capacity of the film–contact interface, while the film does not slip at the lower
contact surface due to the shear stress capacity of the film–contact interface large enough. In boundary film area, the viscosity,
density, and shear elastic modulus of the film are varied across the film thickness due to the film–contact interactions,
and their effective values are used in modeling which depends on the film thickness. In fluid film area, the film does not
slip at either of the contact surfaces, and the shear elastic modulus of the film is neglected. It is found from the simulation
results that the boundary film shear elastic modulus influences are normally negligible on the mass flow through the contact,
the carried load of the contact and the overall film thickness of the contact, and the boundary film shear elastic modulus
would normally influence the local film thickness in an elastic contact when the local film thickness is on the film molecule
diameter scale. It is also found that the boundary film shear elastic modulus effect has the tendency of being increased with
the reduction of the width of a micro contact. It is increased with the reduction of the boundary film–contact interfacial
shear strength or with the increase of the critical boundary film thickness, while it is strongest at certain values of the
contact surface roughness, the width ratio of fluid film area to boundary film area, and the lubricant film shear elastic
modulus.
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Keywords: | Boundary film Fluid film Shear elastic modulus Hydrodynamics |
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