Proceedings of SerbiaTrib '13

nanotribometer. Comparative diagrams of variationof the average values of the dynamic frictioncoefficient, with load and sliding speed, are givenin Fig. 4. It can be seen from presented diagramsthat the sliding speed exhibited no significantinfluence on the friction coefficient. Load increaseproduced very slight decrease of the frictioncoefficient, for all tested conditions.4. CONCLUSIONThis research showed that UHMWPE exhibitslow dynamic friction coefficient (average valuearound 0.1 for all tests) under dry conditions, incontact with alumina. It also showed that low loadsleaded to a bit longer running-in time, but for alltests steady friction state was achieved andmaintained throughout the test with very shortrunning-in periods. Sliding speed change showedno influence on the dynamic friction coefficient.Figure 3. Dynamic friction coefficient curve during drysliding: a) v=4 mm/s, F N =100mN; b) v=12 mm/s,F N =1000mN.ACKNOWLEDGMENTSThis paper is supported by TR-35021 project,financed by the Ministry of Education, Science andTechnological Development of the Republic ofSerbia.REFERENCESFigure 4. a) Friction coefficient as a function of thenormal load; b) Friction coefficient as a function of thenormal load and sliding speed.An average value of the dynamic coefficient offriction (denoted by 'friction coefficient' further inthe text) was calculated, for all test conditions, for asteady state period of friction, as the root meansquare function using the raw data obtained by the[1] S.M. Kurtz: UHMWPE Biomaterials Handbook,Elsevier, London, 2009[2] G. Lewis: Properties of crosslinked ultra-highmolecular-weightpolyethylene, Biomaterials, Vol.22, pp. 371-401, 2001.[3] S.W. Zhang: State-of-the-art of polymer tribology,Tribology International, Vol. 31, pp. 49-60, 1998.[4] P.A. Williams, I.C. Clarke: Understandingpolyethylene wear mechanisms by modeling ofdebris size distributions, Wear, Vol. 267, pp. 646-652, 2009.[5] S. Ge, S. Wang, N. Gitis, M. Vinogradov, J. Xiao:Wear behavior and wear debris distribution ofUHMWPE against Si3N4 ball in bi-directionalsliding, Wear, Vol. 264, pp. 571-578, 2008.[6] V. Banchet, V. Fridrici, J.C. Abry, Ph. Kapsa: Wearand friction characterization of materials for hipprosthesis, Wear, Vol. 263, pp. 1066-1071, 2007.[7] A. Kilgour, A. Elfick: Influence of crosslinkedpolyethylene structure on wear of jointreplacements, Tribology International, Vol. 42,No.11-12, pp. 1582-1594, 2009.[8] J.L. Gilbert, I. Merkhan: Rate effects on themicroindentation-based mechanical properties ofoxidized, crosslinked, and highly crystallineultrahigh-molecular-weight polyethylene, Journal ofBiomedical Materials Research Part A, Vol. 71A,No.3, pp. 549–558, 2004.90 13 th International Conference on Tribology – Serbiatrib’13