The standard combined uncertainties and presented in the Table 2 were calculated uμ uw using Eq. (51) and Eq. (53). By substituting the values of and measured difference we Fn Δµ, obtain . (50) By neglecting negligible terms in Eg. (50) we can write , (51) where the first member is related to the instrument uncertainty of this particular uμi tribometer using the normal force and the second member corresponds to the variance of Fn measured values of friction coefficient μ. The standard combined uncertainties were calculated using Eq. (47) and Eq. (48) and uw measured values of and : . (52) It is apparent that all instrument uncertainties be neglected in comparison with operator induced uncertainty and with variance of values. Thus the uncertainty could be given as A uw . (53) The last experiment was to the investigation of the wear track radius effect on the friction coefficient and the wear rate. We varied radius in the range 3 18 mm using set of five r – samples. The results of this experiment are presented in the in the Table 3 and summarized in Fig. 6. The friction coefficient slightly increases with radius; the increase in the wear rate w μ is even more evident. We can conclude here that the relative humidity in the range 25-41% does not affect the tribological measurement. However, the radius is an important parameter significantly influencing the friction and, particularly, the wear rate. 4.2 Friction and wear of DLC coatings The experiments carried out with ten samples consisted in repeated measurements focused on following parameters and effect on friction and wear rate: (i) operator induced uncertainties of values and further on determination of test parameters impact on values of w and their uncertainties; (ii) relative humidity RH; (iii) normal force (iv) pin velocity µ, w Fn; v. (i) This experiment was arranged in the same way as for TiN coatings referred to above. The pin-on-disk test with parameters = 5 N, = 10 cm/s and = 3000 was carried out and five Fn v N operators measured the wear track cross section area in eight positions evenly distributed
The standard combined uncertainties uμ and uw presented in the Table 2 were calculated using Eq. (51) and Eq. (53). By substituting the values of Fn and measured difference Δµ, we obtain . (50) By neglecting negligible terms in Eg. (50) we can write , (51) where the first member is related to the instrument uncertainty uμi of this particular tribometer using the normal force Fn and the second member corresponds to the variance of measured values of friction coefficient μ. The standard combined uncertainties uw were calculated using Eq. (47) and Eq. (48) and measured values of and : . (52) It is apparent that all instrument uncertainties be neglected in comparison with operator induced uncertainty and with variance of A values. Thus the uncertainty uw could be given as . (53) The last experiment was to the investigation of the wear track radius effect on the friction coefficient and the wear rate. We varied radius r in the range 3 – 18 mm using set of five samples. The results of this experiment are presented in the in the Table 3 and summarized in Fig. 6. The friction coefficient μ slightly increases with radius; the increase in the wear rate w is even more evident. We can conclude here that the relative humidity in the range 25-41% does not affect the tribological measurement. However, the radius is an important parameter significantly influencing the friction and, particularly, the wear rate. 4.2 Friction and wear of DLC coatings The experiments carried out with ten samples consisted in repeated measurements focused on following parameters and effect on friction and wear rate: (i) operator induced uncertainties of w values and further on determination of test parameters impact on values of µ, w and their uncertainties; (ii) relative humidity RH; (iii) normal force Fn; (iv) pin velocity v. (i) This experiment was arranged in the same way as for TiN coatings referred to above. The pin-on-disk test with parameters Fn = 5 N, v = 10 cm/s and N = 3000 was carried out and five operators measured the wear track cross section area in eight positions evenly distributed
Tribo%2520-%2520final%2520corrected2.docx