Comment onThe Relationship Between Friction and Film Thickness in EHD Point Contacts in the Presence of Longitudinal Roughness by Guegan, Kadiric, Gabelli, & Spikes

Guegan and coworkers have addressed the important problem of friction of elastohydrodynamic contacts in the mixed regime. Any attempt at understanding friction in the mixed regime must address the friction in the full-film regime. To analyze fiction for the full film, they used a common, but unsupported, assumption that the friction curve is a rheological flow curve. The inconsistency can be demonstrated by integration over the contact with the assumed Eyring equation employing the known pressure dependence of the viscosity and also by a full numerical simulation which yields the same sinh friction curve without using the Eyring assumption.