The role of the glass transition for EHL minimum film thickness

When the glass transition is considered in an EHL traction analysis, shear-thinning is not sufficient to explain experiments because there is no liquid behavior to shear-thin and a limiting stress is required. The usual approach of ignoring the glass transition and the associated previtreous pressure dependence has concealed the role of vitrification in establishing the minimum film thickness in real contacts. For the first time, the glass transition is considered in an elastohydrodynamic lubrication simulation along with the glass compressibility. Vitrification and the previtreous pressure response are necessary to predict the minimum film thickness in a point contact. Future numerical simulations should include the glass transition, both for the film thickness and, of course, friction.