A MATHEMATICAL, GEOMETRICAL WEAR MODEL FOR CONTINUOUS WEAR MEASUREMENTS BASED ON THE NORMAL APPROACH BETWEEN A SPHERICAL AND A FLAT SPECIMEN SUBJECT TO FRETTING

Fretting wear occurs when normally loaded surfaces are subject to osci llatory relative tangential movements with small amplitude. As a resul t, the fretting wear volumes are much smaller than macroscopic wear vo lumes and by consequence are much more difficult to measure. Usually, qualitative or semi-quantitative but discontinuous techniques are used to measure fretting wear (SEM, scar size measurements, 3D topography) . This means that the wear can be measured only at the end of the expe riment and that many experiments are required in order to obtain a wea r curve (wear as a function of number of cycles). In this work it will be shown that continuous measurement of the normal approach between t he specimens can be used to obtain wear curves of both test specimens separately. Apart from measuring the normal approach during the test, correct measurement of the wear volumes of both specimens at the end o f the experiment is needed. Thin layer activation (TLA) is used for th is measurement. A suitable, geometrical wear model is used to obtain c ontinuous wear curves based on the above data. This paper describes th e geometrical wear model used and the procedure to convert normal appr oach measurements into wear volume curves. Some experimental data are used to illustrate the application of the wear model. (C) 1997 Elsevie r Science S.A.