An Inlet Computation Zone Optimization for EHL Line Contacts

Abstract

Most EHL numerical calculation methods considering both starved and flooded conditions, employ a fixed multiple of the Hertzian radius for the normalization of the computational domain. These methods are often used to investigate the influence of the lubricant supply on friction etc., but the solutions obtained might be numerically starved. The present numerical calculation method utilizes an optimized normalization of the computational domain to ensure that the solutions obtained are not numerically starved. With this normalization method, the computational domain can be appropriately meshed, regardless of the variability in the inlet length due to changes in the operating conditions. This method can, therefore, be used to obtain accurate EHL film thickness and pressure data over a wide range of operating conditions.

A traction coefficient formula for EHL line contacts operating in the linear isothermal region

“…[31]. The EHL line contact numerical calculation model employed in this paper incorporates Roeland's viscosity-pressure relationship and Dowson and Higginson's density-pressure relationship, and it has been verified against available results [22]. At high load conditions, the oil pressure distribution has fluctuations.…”

“…A non-dimensional model for numerical calculation with which numerical starvation can be avoided is adopted here. This is realized by the introduction of a parameter b ′ , which defines an inlet length that ensures that numerical starvation does not occur [22]. More precisely, in order to ensure fully-flooded conditions, the computational domain for the EHL line contact model employed in the present analysis is normalized with the inlet distance b ′ = a + S f , instead of the Hertzian radius a.…”

“…This kind of model has been used in many investigations since then. One example can be found in [1], where an attempt to give a quantitative identification of the four most commonly encountered traction regimes by utilizing dimensionless numbers were presented, other examples are [17][18][19][20][21][22][23][24].…”

“…In this case, the impact of thermal effects and the shearthinning behavior of the lubricating fluid is expected to be negligible and they are, therefore, not considered in the present analysis. The prediction formula is a curve fit, based on the results obtained using a fully-coupled finite element approach for the EHL line contact assuming isothermal conditions [22]. Finally, to improve the applicability, we combined our prediction formula with Bair's approximate expression for the traction coefficient for dry sliding, including the effect of roller compliance [27].…”

Optimization of the computational domain for EHL point contacts

“…In our previous work [19], the inlet distance of an EHL line contact was normalized based on the experimental results of Wedeven et al [15], who discovered that the onset of starvation occurs if the ratio of the oil film thickness at the inlet boundary to the central oil film thickness falls below 9. The EHL point contact model presented herein utilizes the same type of optimized computational domain and does, therefore, constitute an extension of this model.…”