An experimental study on the concentration and shape of dents caused by spherical metallic particles in EHL contacts
Résumé
An experimental study of metallic contaminant effects on surface indentation in EHL contacts is presented. Particles roe initially spherical and are composed of M50 high-carbon steel powder. Their diameter ranges from 32 to 40 mu m An original lubrication system with a controlled level of contamination was built. The contaminant distribution and concentration are measured on-line by an automatic particle counter. Tests are conducted on a two-disk machine with different operating conditions. Particles may travel through the EHL contact only one time, the lubricant flow being used only once. The oil is a synthetic one qualified under the MIL-L-23699 specification. An optical profilometer is used to describe the indent topography and a CCD video camera to count the number of dents. The test bench is described and the experimental procedure is presented. Specific tests were performed to qualify the contamination bench. The combined effects of particles concentration and test duration on dent distribution were studied. Some results on the shape and concentration of indents versus operating conditions are presented. It is shown that over the range of test conditions considered, the number of indents on the raceways can be estimated from the particle concentration in the oil bulk. This leads to the conclusion that the particle entry ratio is close to one, i.e., the concentration of particles inside the EHL contact is close to those in the bulk.