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Movement of Entrapped Oil Under Pure Rolling Conditions

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Abstract

This article presents a study on the movement of an oil entrapment (or impact dimple) in a pure rolling elastohydrodynamic lubricated (EHL) contact. The oil entrapment was formed by impacting a steel ball against a lubricated glass disc. The contact was then activated under pure rolling conditions, and the movement of the entrapped oil was visualized by optical interferometry. It was found that during the movement of the dimple within the EHL contact, there exists a critical value for the displacement of dimple core. For the displacement of the dimple core less than the critical value, the dimple moves at the entrainment velocity and the film thickness of dimple core remains almost constant. For displacement beyond the critical value, the dimple slows down and its depth decreases rapidly. The effects of influential factors such as speed, initial dimple depth, load, and initial gap size were theoretically and experimentally investigated.

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Abbreviations

a :

Acceleration of ball, m/s2

b :

Hertzian semi-contact width, m

d :

Displacement, m

d c :

Critical displacement of dimple core, m

E′:

Equivalent elastic modulus, Pa

F :

Force, N

h :

Film thickness, m

h 00 :

Rigid separation, m

h core :

Film thickness of dimple core, m

h d,o :

Initial dimple depth, m

h g,o :

Gap at the instant of impact process completed, m

h out :

Minimum film thickness at the outlet region, m

m :

Mass of ball, kg

p :

Pressure, Pa

R x , R y :

Equivalent radius of contact bodies, m

t :

Time, s

△t :

Time step, s

u :

Velocity, m/s

u b, u d :

Velocity of ball and disc, respectively, m/s

u e :

Entrainment velocity, m/s

u core :

Velocity of dimple core, m/s

v :

Approach speed of ball during impact process, m/s

W :

Applied load, N

w :

Resistance of lubricant, N

x, y, z :

Coordinates, m

η :

Viscosity of lubricant, Pa s

ρ :

Density of lubricant, kg/m3

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Acknowledgements

The authors would like to express their thanks to the financial supports from the Research Grants Council of Hong Kong, China (Project No. 9041385) and the Natural Science Foundation of China (Project No. 50875136).

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Authors and Affiliations

  1. School of Mechanical Engineering, Qingdao Technological University, 11 Fushun Road, Qingdao, 266033, People’s Republic of China

    X. M. Li & F. Guo

  2. Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People’s Republic of China

    X. M. Li & P. L. Wong

Authors
  1. X. M. Li
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  2. F. Guo
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  3. P. L. Wong
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Correspondence to P. L. Wong.

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Li, X.M., Guo, F. & Wong, P.L. Movement of Entrapped Oil Under Pure Rolling Conditions. Tribol Lett 43, 129–137 (2011). https://doi.org/10.1007/s11249-011-9811-9

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