Lube-Tech
This test method gives a very good presentation of dynamic wetting and creep effects, but if there are stable conditions at the interface between lubricant and surface, a further differentiation is difficult. Questions like “Is adhesion strong enough?”, or “Is there even an oil repelling effect?”, “Is oil removed due to gravity or centrifugal forces?”, cannot be answered.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.117 page 3
Dynamic Adhesion Measurement Within the scope of a development project3
a test
method has been developed which allows one to dynamically measure the adhesive force of a lubricant drop directly on the respective materials and surfaces. The developed APG Adhesion Tester (Figure 3) is based on the technology of a centrifuge.
On a rotating disk maximum six standardised plates (size 76 x 26mm, Figure 4) out of any material (i.e. glass, metals, plastics) can be easily positioned with clamping claws. A pattern on the base of the disk with different radii from 30 to 95 mm allows us to find the correct position for the oil drops. Normally we work with three drops per radius.
It is also possible to make tests on other components or parts by fixing them anywhere on the disk with shiftable magnetic strips (Figure 5). The shifting forces of the magnets are higher than the maximum centrifugal acceleration.
Figure 3. APG Adhesion tester with rotating disk and dosing unit (swivelling)
Figure 5. Easy fixing of varying forms of test specimen with magnetic strips
Now oil droplets with a defined volume are selectively positioned on the material surfaces in different radii, and are subjected to different graduated centrifugal
Figure 4. Rotating disk with test samples containing oil droplets on different radii
accelerations (an varying from 1.1 to 41.7 m/s²) when the disk rotates. From the specific gravity, the drop volume, the distance from the axis of rotation and the
32 LUBE MAGAZINE NO.146 AUGUST 2018
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