This work investigates the effect of lubricant rheology on friction in coated elastohydrodynamic contacts. Two lubricants with relatively different properties are selected and two coating configurations are considered. The first coating type consists of a soft material with a low thermal inertia while the second is a hard material with a high thermal inertia. The former is known to decrease friction while the latter increases it compared to uncoated contacts. The original expectation was that the lubricant with higher P–T dependence of viscosity would exhibit higher relative friction deviation from the uncoated case. It turned out that this is only true in the linear and thermoviscous friction regimes at low and high slide-to-roll ratios, respectively.
MasjediMKhonsariM. Theoretical and experimental investigation of traction coefficient in line-contact EHL of rough surfaces. Tribol Int2014; 70: 179–189.
2.
XuGSadeghiF. Thermal EHL analysis of circular contacts with measured surface roughness. ASME J Tribol1996; 118: 473–482.
3.
BjörlingMLarssonRMarklundP. Elastohydrodynamic lubrication friction mapping – The influence of lubricant, roughness, speed, and slide-to-roll ratio. Proc IMEchE, Part J: J Engineering Tribology2011; 225: 671–681.
4.
BogdsanskiS. Effect of coatings on thermal conditions of EHL. Lubric Sci1995; 8: 61–72.
5.
EvansRDCogdellJDRichterGA. Traction of lubricated rolling contacts between thin-film coatings and steel. Tribol Trans2009; 52: 106–113.
6.
KalinMVelkavrhIVižintinJ. The Stribeck curve and lubrication design for non-fully wetted surfaces. Wear2009; 267: 1232–1240.
7.
BjörlingMIsakssonPMarklundP. The influence of DLC coating on EHL friction coefficient. Tribol Lett2012; 47: 285–294.
8.
BjörlingMHabchiWBairS. Friction reduction in elastohydrodynamic contacts by thin layer thermal insulation. Tribol Lett2014; 53: 477–486.
9.
HabchiWEyheramendyDVergneP. Stabilized fully-coupled finite elements for elastohydrodynamic lubrication problems. Adv Eng Softw2012; 46: 4–18.
10.
HabchiW. Thermal analysis of friction in coated elastohydrodynamic circular contacts. Tribol Int2016; 93: 530–538.
11.
BobachLBartelDBeilickeR. Reduction in EHL friction by a DLC coating. Tribol Lett2015; 60: 17–17.
12.
BobzinKBrögelmannT. Minimizing frictional losses in crankshaft bearings of automobile powertrain by diamond-like carbon coatings under elastohydrodynamic lubrication. Surf Coat Technol2016; 290: 100–109.
13.
BeilickeRBobachLBartelD. Transient thermal elastohydrodynamic simulation of a DLC coated helical gear pair considering limiting shear stress behavior of the lubricant. Tribol Int2016; 97: 136–150.
14.
HabchiW. Influence of thermo-mechanical properties of coatings on friction in elastohydrodynamic lubricated contacts. Tribol Int2015; 90: 113–122.
15.
BjörlingMLarssonRMarklundP. The effect of DLC coating thickness on elastohydrodynamic friction. Tribol Lett2014; 55: 353–362.
16.
MurnaghanFD. The compressibility of media under extreme pressures. Proc Natnl Acad Sci1944; 30: 244–247.
17.
RolandCMBairSCasaliniR. Thermodynamic scaling of the viscosity of van der Waals, H-bonded, and ionic liquids. J Chem Phys2006; 125: 4508–4508.
18.
BairSCasaliniR. A scaling parameter and function for the accurate correlation of viscosity with temperature and pressure across eight orders of magnitude of viscosity. J Tribol2008; 130: 041802–041802.
19.
HabchiWVergnePBairS. Influence of pressure and temperature dependence of thermal properties of a lubricant on the behaviour of circular TEHD contacts. Tribol Int2010; 43: 1842–1850.
20.
BairSQureshiF. Accurate measurements of pressure-viscosity behavior in lubricants. STLE Tribol Trans2002; 45: 390–396.
21.
BairS. The high pressure rheology of some simple model hydrocarbons. Proc ImechE, Part J: J Engineering Tribology2002; 216: 139–149.
22.
BairS. A rough shear thinning correction for EHD film thickness. STLE Tribol Trans2004; 47: 361–365.
23.
LiuPYuHRenN. Pressure–viscosity coefficient of hydrocarbon base oil through molecular dynamics simulations. Tribol Lett2015; 60: 1–9.
24.
BairSWinerWO. The high shear stress rheology of liquid lubricants at pressures of 2 to 200 Mpa. ASME J Tribol1990; 112: 246–252.
25.
Nagata Y. EHD phenomena in grease lubricated contacts. PhD Thesis, University of Sussex, UK, 2011.
26.
HabchiWBairSVergneP. On friction regimes in quantitative elastohydrodynamics. Tribol Int2013; 58: 107–117.
27.
BairSVergnePKumarP. Comment on “History, origins and prediction of elastohydrodynamic friction” by Spikes and Jie. Tribol Lett2015; 58: 16–16.
28.
HabchiW. A numerical model for the solution of thermal elastohydrodynamic lubrication in coated circular contacts. Tribol Int2014; 73: 57–68.
29.
BirdRBArmstrongRCHassagerO. Dynamics of polymeric liquids, Vol.: 1 Fluid mechanics, 2nd ed. New York: Wiley, 1987, pp. 94–94.
30.
BairSKotzalasM. The contribution of roller compliance to elastohydrodynamic traction. STLE Tribol Trans2006; 49: 218–224.
31.
BairS. High-pressure rheology for quantitative elastohydrodynamics, Amsterdam: Elsevier Science, 2007, pp. 173–174.
