ON THE WEAR DEBRIS OF POLYETHERETHERKETONE - FRACTAL DIMENSIONS IN RELATION TO WEAR MECHANISMS

It has been recognized that wear debris contains extensive information about wear and friction of materials. Investigation of wear debris is important for tribological research. In order to find out an effectiv e way that is able to diagnose and predict the wear state of polymers, the authors investigated the relationship between the wear debris mor phology and the wear behaviour of the bulk material. Polyetheretherket one (PEEK) was employed as the model material. Its sliding wear and fr iction properties were measured by means of a pin-on-disc apparatus. A t a constant sliding velocity of 1 m s(-1), the specific wear rate was independent of load under lower loading conditions (1-4 MPa) but incr eased with a rise in load under higher loading conditions (4-8 MPa). T he coefficient of friction was insensitive to the variation of contact pressure. The possible mechanisms involved were analysed on the basis of the wear debris morphology as well as the wear performance. Fracta l geometry, which describes non-Euclidean objects, was applied to the quantitative analysis of the boundary texture of the wear debris due t o the fact that the qualitative assessment of the wear debris morpholo gy was not effective enough to reflect the geometrical variation of th e fragmental shapes. The experimental results demonstrated that the we ar debris were fractals, and could be characterized with the fractal d imensions which were determined by the slit island method. In addition , it was found that the fractal dimension of the wear debris was close ly related to the wear behaviour of PEEK, and can be regarded as a mea sure of wear rate. Copyright (C) 1996 Elsevier Science Ltd