Microtextured surfaces in higher loaded rolling-sliding EHL line-contacts

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

“…A reduction of friction up to 12% compared to the references was achieved by micro-texturing. It can be assumed that the solid-solid contact ratio was reduced during contact between the counter-body and the texture [49]. In addition, the build-up of an additional hydrodynamic pressure can be expected.…”

“…This measure corresponded to area coverage of approximately 10%. The values were chosen as they were advantageous as described in the literature and previous studies [49,50].…”

“…Tribological testing was carried out on a single cam/single bucket tappet component test-rig (TSRP, KTmfk, Erlangen, Germany), as described by Dobrenizki et al [44], Marian et al [49], and Tremmel et al [50]. This testing is illustrated in Figure 1c, utilizing standard valve train parts (cam, spring, valve) to ensure realistic conditions.…”

“…To evaluate the solid friction of uncoated and coated specimens, we performed unlubricated ball-on-disk test (K-SST, KTmfk, Erlangen, Germany) under constant climatic conditions (relative humidity of 40 ± 5% at 23 ± 2 • C); noting that the specimens significantly affect the frictional behavior under mixed lubrication typical for cam/tappet-contacts [49]. Hardened 100Cr6 bearing balls with a diameter of 9.5 mm served as counter-bodies.…”

“…They showed that lubricant drawn out from the micro-pockets helped to separate the rubbing surfaces especially under thin-film conditions where the counter-bodies featured opposing sliding speeds. Employing a component test-rig, Marian et al [49] studied the tribological performance of shallow line-shaped microtextures applied on tappets in the cam-contact operating under mixed lubrication conditions. For pure mineral oil, a significant friction reduction of up to 14 % was determined, which correlated well with measurements from an electrical resistivity circuit.…”