CFD modeling compared to temperature and friction measurements of an EHL line contact

Abstract

In this paper, predictions from CFD modeling are compared against measurements of surface temperatures and friction for an EHL line contact lubricated with the fluid Santotrac 50. Two slide-to-roll-ratios (SRR), 50% and 100%, and entrainment velocities ranging from 0.211 to 1.13 m/s are considered. Very good agreement is shown for the 50% SRR cases, with only a 3% deviation in friction coefficient values. At 100% SRR, the deviation in friction increases to 3-7% which is attributed to deficiencies in the modeling approach with regard to shearthinning. The temperature profiles agree reasonably well at 50% SRR and show larger deviations at 100% SRR. For all cases, the formation of a shear-band in the center of the fluid film is predicted. This is very pronounced for 100% SRR, although likely to be over-estimated by this CFD-approach. The data presented here serve as a basis from which further refinements in the modeling and measurements shown can be made.

A Computational Fluid Dynamics Study on Shearing Mechanisms in Thermal Elastohydrodynamic Line Contacts

“…This indicates that the choice of a rheological model and/or lubricant properties, at higher pressure levels, can cause significant deviation between numerical simulations and experimental measurements. This is in agreement with the recent study by Hartinger [25], who concluded that at the pressure of about 0.6 GPa, his CFD model of the EHL line contact problem overestimates shear-thinning effect on viscosity when compared to experimental measurements of friction and surface temperatures.…”

“…where τ 0 is the Eyring stress that denotes the threshold where the Newtonian fluid behavior ends and the non-Newtonian fluid behavior starts. To avoid division by zero, instead of η 0 in Equation (29) Hartinger [25] suggests using the Houpert equation (Equation (25)). In addition, to avoid numerical error during simulation, Hartinger also recommends using the Ree-Eyring model only if strain rate is larger than an arbitrarily chosen minimum value of .…”

“…In addition, to avoid numerical error during simulation, Hartinger also recommends using the Ree-Eyring model only if strain rate is larger than an arbitrarily chosen minimum value of . γ = 1 × 10 −8 s −1 , otherwise he suggests using Houpert equation [25]. This can be written in the following fashion…”

“…Finally, in order to use Equation (35), it is recommended that the Peclet number is larger than 5 [24]. In 2018, Hartinger [25] showed that for the EHL line contact problem, surface temperatures predicted by Carslaw-Jaeger equation closely matched experimental measurements.…”

A review of recent advances in tribology

“…In parallel to the popular numerical solver based on finite difference discretization, many researchers rely on the finite element method (FEM) to solve the equations involved in lubrication and solid contact [590,599,611], and CFD-based commercial software has become a popular tool in analysis of EHL, which could provide critical information for across-film distributions of velocity, temperature, and viscosity [597,612].…”