Experimental and numerical studies of positive texture effect on friction reduction of sliding contact under mixed lubrication

Abstract

Textured surfaces have been remarkable in improving the frictional performance of sliding contacts, particularly at instances such as boundary or mixed lubrication regimes. This article reports the results of an experimental and numerical study carried out by introducing surface textures in the form of protrusions to investigate its effects on friction performance under a mixed lubrication regime. The surface textures produced by the chemical etching process are tested on the pin on disc test rig by varying area density and height of the texture. In numerical simulation, the modified Reynolds equation (Patir–Cheng flow model) and asperity contact model (Greenwood–Tripp model) are solved for hydrodynamic and asperity pressures, respectively. The results indicate that the experimental measurements are qualitatively in good agreement with numerical predictions. Furthermore, the simulations are performed for different texture shapes by varying texture area density, height, and sliding velocity. The results depict that a maximum friction reduction of 87% with elliptical textures compared to the un-textured case.

Research on different structures of dimpled textures on improving the LE-FPL of engine

“…The impact of the W 0 is maximum at the mixed lubrication regime, thus, W ac and F f are also maximum, these results are similar as in Refs. (Xiang et al , 2019; Babu et al , 2020). With the bearing surface added by dimpled textures, the results show that all the W ac , F f , and COF of the rod bearing are remarkably reduced in comparison without dimples.…”

“…However, if the distribution density of the SD in the y -direction is further increased, the distance between the dimples in the y -direction is smaller. Resulting in increasing the cavitated region (Wang et al , 2011; Gropper et al , 2016), thus the increase of the p is also limited, while both the F f and COF are increased (Babu et al , 2020). As shown in Figure 9, the MAX p with SD ( m = 18) is 207.4 MPa and it is reduced by 7.4% in comparison with the MAX p with SD ( m = 12) in Figure 7(c).…”

“…The studies in Refs. (Xiang et al , 2019; Babu et al , 2020) suggested that the increase of the oil film thickness and pressure ( h and p ) in the mixed lubrication regime could reduce solid contact and friction.…”

“…However, it is difficult to enhance the h and p if only via the optimal dimensions of the rod bearings. To solve this issue, the surface textures were added on the bearing surface of journal bearings to reduce the solid contact and friction (Zhang et al , 2017; Gropper et al , 2016; Tomanik, 2013), the dimple parameters such as depth, area density, and shape were also optimized, they reported a friction reduction of 50% at a depth of 5 µm and area density of 25% (Babu et al , 2020). Besides, the circular dimples (CD) designed on the shaft surface to reduce the friction were studied via the experiment.…”

“…The effect of the distribution density and shape of the multi-shape dimples on improving the friction and lubrication was investigated and optimized on friction pairs (Zhang et al , 2017; Pei et al , 2011; Rosenkranz et al , 2019a; Grützmacher et al , 2019). The researches indicated that with the texture’s depth from 5 to 20 µ m, the solid asperity contacts and friction were significantly decreased, particularly from 5 to 5.5 µ m with the CD or SD (Babu et al , 2020; Jiao et al , 2020; Rosenkranz et al , 2019b). Based on the outstanding advantages of the CD or SD, the bearing surface of journal bearings was also designed by the CD or SD to improve lubrication and friction between the shaft and bearing surfaces (Gropper et al , 2016; Hu et al , 2019; Martan et al , 2020).…”