The Film Thickness in Piezoviscous Regime; Film Thickness Regimes Transition Criteria1

Johnson [4] showed in his magisterial 1970 paper that lubrication regimes play a decisive roll in the determination of the film thickness in a counterformal contact under full film lubrication conditions. The numerical and pictorial definition of the transition areas between these regimes deserves careful attention. The author has elaborated this topic for elliptical contacts with arbitrary ellipticity ratio. In addition, he has derived a film thickness equation for the so-called piezoviscous rigid (PVR) lubrication regime. The author deserves congratulations for this welcome addition to the literature. The following is a rather long commentary on the author's ideas, and some occasional queries on the consequences