Knowledge of the flow profile is necessary to identify sources of traction in an elastohydrodynamic contact. Yet, there has been little work on the direct measurement of flow, as the nanoscopic film thickness prevents the use of conventional techniques.Photobleached-fluorescence imaging was used to obtain the first experimental flow profile within an elastohydrodynamic contact. The investigated lubricants show multiple flow phenomena and do not follow the predicted Couette flow, often assumed in tribology theory.Two distinct flow conditions were observed: a transition from Couette flow to a non-linear velocity profile and either shear banding or dilation. Both conditions were shown to depend on the position in the contact and the shear rate. Causes, such as the pressure gradient and the critical shear stress of the lubricant are discussed, as well as the effect on traction.

Experimental flow profiling in an elastohydrodynamic contact

244th National Meeting (2012)

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