Comparison of Transient EHL Calculations with Start-up Experiments

摘要

The paper presents numerical results for the elastohydrodynamic lubrication of point contacts where the entrainment velocity is increased with time from an initial value of zero. The cases considered correspond to experimental work presented by Glovnea and Spikes for the case of a stationary dry contact that is brought into elastohydrodynamic operation by a controlled angular acceleration of one of the contacting bodies. The experiments modelled involve simple sliding of a steel ball on a stationary glass disk, with the entrainment velocity increased uniformly, at different rates, to a steady state value. The steady state characteristics of the test case, which is reached by all experiments after different times, are used to select appropriate values of the lubricant parameters for incorporating in a transient numerical analysis of the start-up test conditions. The paper compares the numerical results obtained using a differential deflection point contact transient analysis with the detailed published experimental film thickness measurements presented by Glovnea and Spikes. Differences in the calculated and experimental behaviour are observed, particularly at the highest acceleration rates. An explanatory factor to account for the differences is proposed.