Lube-Tech Upper specimen:


Steel ball 10 mm, polished, DIN 51834, material: 100Cr6


The greases will be applied onto the surface using a special grease caliber, so the quantity of the grease is fixed for all tests.


2.3.2. Test matrix for the tribological investigation


The first two standard methods (determination of friction and wear properties of lubricating greases) have been run for all tests. In Table 3 the most important test parameters of the standard tests are summarised, and in Table 4 the complete test matrix for all SRV®


tests can be found. Figure 2: Demonstrates the behavior of the friction coefficient of Grease F Table 3: Test parameters for the chosen SRV® standards


Figure 3 illustrates the wear scar on the disk and ball at the end of the test for Grease F made by a microscope. The measured wear values according to ASTM D7755 can be carried out by tip stylus profilometer or laser scanning microscope.


PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE


No.136 page 4 Mean contact pressure Pm = 1.84 Gpa & Maximum contact pressure Pmax = 2.76 Gpa


Figure 2 shows exemplary a COF (coefficient of friction) progression for Grease F.


Table 4: Test matrix for SRV®


tests


3. Results of friction and wear measurements The following part of the study was conducted using the SRV rig according to ASTM D5707 under the following test parameters: • Temperature: • Load:


• Stroke:


• Frequency: • Time:


80 °C 200 N 1 mm 50 Hz


2 hours


With 200 N normal load the calculated Hertzian pressures are:


32 LUBE MAGAZINE NO.165 OCTOBER 2021


Figure 3: Wear scar on the ball (left), wear scar on the disk (right)


After measuring the diameter of wear scar on the ball as well as the width and length of the wear scar on the disk (Figure 3), the planimetric perpendicular surface area (Figure 4) and using the formula written in standard ASTM D7755, the wear volume can be calculated.


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