As regards the evaluation of wear mass loss, it has not been
possible to evaluate it with gravimetric methods because the
available precision balance has an accuracy of 0.1 mg whereas theresults are approximately of 105 g for the tests under dry conditions.
Therefore, with the purpose of comparing the wear rates
of the three tribological pairs under study, the worn surfaces of the
UHMWPE specimens, after the tests, were analyzed by 3D Optical
Surface Metrology System Leica DCM 3D (Fig. 7) of the LIMIT Lab at
the ETSIDI – Technical University of Madrid, only in the case in
which the pins' diameter was of 6 mm. By knowing the density of
UHMWPE (0.93 g/cm3
) [22], it was possible to estimate the wear
mass loss by measuring the groove volume left by the pin on the
specimens during the tests. For the tests carried out under lubricated
conditions it was no possible to evaluate the wear mass loss
for, as it will be detailed in results section later on, most of tests
have lead to the breaking of the lubricant fluid film on both the
UHMWPE