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Tribology

Engineered surfaces in sliding and rolling contact

This has been an active area of research in CUED since the pioneering work of K L Johnson on the plastic flow and shakedown of surfaces in the early 1960's when the shakedown limit was established as the rational design criterion for rolling contacts (wheels and rails, rolling bearings, traction drives, etc.). Methods for estimating its value have been drawn up and reviewed and implications for surface life considered [1-3]. Two current avenues based on this earlier work have recently been explored. Shakedown principles have been applied in the analysis of the changes in surface topography which take place during repeated sliding contacts in metals [4-6]: progressive plastic flow of asperities leads to the formation of very thin, filmy wear debris [7] by a process of plastic ratchetting brought about by the repeated pummelling of the softer surface by the asperities on the harder. A model for this mild wear regime, which is driven by normal loads rather than by friction, has been developed [8,9]; the hardness of the wearing surface and the coefficient of friction at the interface influence the wear rate thought their effect on the plasticity index for repeated sliding introduced in [8]. In addition, some studies have been made on the application of shakedown principles to surfaces whose strength properties vary with depth as a result of surface engineering by both thermo-chemical hardening [11,12] as well as the more complex cases of coated surfaces: in such cases, not only both the elastic and plastic material properties vary with depth, but account must be taken of the integrity of the bond between coating and substrate [13-16].

Relevant/recent publications

  1. Johnson, K. L. 'The application of shakedown principles in rolling and sliding contact' Eur. J. Mech., A/Solids, 11, pp155-172 (1992).
  2. Johnson, K. L. 'Contact mechanics and the wear of metals' in Proceedings of Austrib 94, Perth (1994).
  3. Williams, J. A., Dyson, I. N. and Kapoor, A. 'Repeated loading, residual stresses, shakedown and tribology' Journal of Materials Research., 14, pp1548-1559 (1999).
  4. Johnson, K. L. and Shercliff, H. R. 'Shakedown of two-dimensional asperities in sliding contact' Int. J. Mech. Sci, 34, pp375-394 (1991).
  5. Kapoor, A and Johnson, K. L. 'Steady state topography of surfaces in repeated boundary lubricated sliding' Proc. 19th Leeds/Lyon Symposium on Tribology (ed. Dowson, D.) Leeds, (1992).
  6. Kapoor, A. and Johnson, K. L. 'Effect of changes in geometry on shakedown in rolling and sliding contact' Int. J. Mech. Sci., 34(3), pp223-239 (1991).
  7. Kapoor, A. and Johnson, K. L. 'Plastic ratchetting as a mechanism of filmy wear in repeated sliding' Proc. Roy. Soc., A445, pp367-381 (1994)
  8. Kapoor, A., Johnson, K. L. and Williams, J. A. 'The steady state sliding of rough surfaces' Wear, 175, pp81-92 (1994).
  9. Kapoor, A., Johnson, K. L. and Williams, J. A. 'A model for the mild ratchetting wear of metals' Wear, 200, pp38-44 (1996).
  10. Williams, J. A. 'Wear modelling: analytical, computational and mapping: a continuum mechanics approach' Wear, 225-229, pp1-17 (1999).
  11. Kapoor, A. and Williams, J. A. 'Shakedown limits in sliding contacts on a surface-hardened half-space' Wear, 172, pp197-206 (1997).
  12. Kapoor, A. and Williams, J. A. 'Shakedown limits in rolling and sliding point contacts on an anisotropic half-space' Wear, 191, pp256-260 (1996).
  13. Kapoor, A. and Williams, J. A. 'The effect of interfacial shear strength on the performance of coated surfaces in repeated sliding' J. Tribology, 119, pp1-8 (1997).
  14. Wong, S. K., Kapoor, A. and Williams, J. A. 'Shakedown limits on coated surfaces' Thin Solid Films, 292(1-2), pp156-163 (1997).
  15. Wong, S. K., Kapoor, A. and Williams, J. A. 'Shakedown limits on coated and engineered surfaces' Wear, 203-4, pp162-170 (1997).
  16. Dyson, I. N., Williams, J. A. and Kapoor, A. 'The effect of surface hardening on the shakedown of elliptical contacts' J. Engineering Tribology, 213, pp287-298 (1999).

Contact Details

For further information on the work summarised above contact Dr J A Williams at Cambridge University Engineering Department, Trumpington St, Cambridge, CB2 1PZ, UK. Tel: 01223 332641, Fax: 01223 332662. E-mail: jaw@eng.cam.ac.uk
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