Abstract
An original dynamic tribotest was used to study the friction response of two kinds of tribological surface: zinc-dialkyl-dithio-phosphate (ZDDP) thermal film and ZDDP tribofilm. This apparatus allows friction to be determined with no need for measuring tangential force. A velocity dependent friction contribution was found in each case in addition to a velocity independent one, showing the viscous character of such films. Furthermore, during test on ZDDP thermal film, the viscous damping represents 18% of the total dissipated energy as it is 16% for ZDDP tribofilm.
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The authors would like to thank T. Le Mogne for the help on X-ray photoelectron spectroscopy analyses, JX Nippon Oil and Energy Corporation for providing lubricants and ANR for support in the ANR-07-JCJC-0060 LOWPOLUB project. They are also grateful to Institut Carnot I@L for partially funding the experimental equipment.