Negative Pressures under a Lubricated Piston Ring

Abstract

Large negative pressures have been observed in the oil film lubricating a piston ring. Just after the dead-centre position, these reach a peak value of −0.78 MN/m2 (-113.1 lbf/in2), which is far in excess of the values normally assumed to be needed to produce cavitation. They are only sustained for a short period of time, but have the important effect of reducing the minimum film thickness.