Recent experiments have shown direct evidence of shear banding in the flow of some fluids at high shear rates and pressures, a typical example being lubricants in elasto-hydrodynamic (EHD) contacts. Interestingly, the same fluids have been found to shear when in contact with certain materials but not when in contact with others under the same conditions. This indicates that shear banding is not a purely rheological phenomenon. Instead, it is a result of the mechanical and thermal interaction between the fluid and the confinement, as well as a result of the fluid properties and their sensitivity to shear, pressure and temperature. In this paper, a detailed analysis is performed to show that shear banding appears for piezoviscous fluids under appropriate boundary conditions if a coupled solution is sought to the elastic, thermal and hydrodynamic problem of flow in tribological systems. In particular, it is shown that shear banding arises from a stability problem formally similar to a buckling problem. The implications for friction and slip are discussed.

Shear banding of piezoviscous fluids as a stability problem

253rd National Meeting (2017)

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