PSI - Issue 12

Francesca Curà et al. / Procedia Structural Integrity 12 (2018) 44–51 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Table 4. Experimental results of Pin-on-Disk tests. GNP % Oil 1

Oil 2

Grease St. Dev.

Mean CoF

St. Dev.

% Diff.

Mean CoF

St. Dev.

% Diff.

Mean CoF

% Diff.

0

0,116 0,095 0,112 0,127

0.011 0.013 0.018 0.019

-

0.095 0.095 0.085 0.093

0.011 0.013 0.013 0.016

-

0.130 0.111

0.020 0.010

-

0.5

-18.2

0.6

0,6

2 5

-3.9

-10.7

-

-

-10,7

9.8

-2.2

0.097 0.114

0.006 0.000

-2,2

10

-

-

-

-

-

-

-

As an example, Figure 3 shows the CoF trend during a Pin-on-Disk test for Oil 2 + 5% GNP. Figure 4 reports Pin-on-Disk results in terms of CoF values for three lubricants (Oil 1, Oil 2, Grease) and for all percent of GNP (0, 0.5, 2, 5, 10%). It may be observed that the maximum percent of GNP chosen for grease (10%) is higher than that used for oils (5%). This is due to the different viscosity of lubricants and to the different behaviour in the mixing phase; as a matter of fact, the grease allows the use of a higher concentration of GNP without creating heterogeneity in the compound.

Fig. 3. CoF trend during the Pin - on - Disk test for Oil 2 + 5% GNP.