Attempt to Measure the First Normal-Stress Difference N(1) in Shear Flow for a Polyisobutylene/Decalin Solution 'D2b' at Shear Rates up to 10 to the 6th Power/S.

摘要

It is well known that the state of stress for viscoelastic liquids in steady shear flow is determined by a stress sigma and by N1 and N2, the first and second normal stress differences, together with an isotropic contribution which is not of direct rheological significance. The need to measure sigma and N1 at shear rates equal to or greater than 10 to the 6th power/s has been increasingly recognized in recent years in connection with paper coating and journal bearing lubrication, for example. Recent results on commercial multigrade oils suggest that N1 can contribute as much as the viscosity contributes to the minimum oil film thicknesses in a front main journal bearing of a V-6 engine running at 3000 rpm; since N1 is associated with conservative forces, these results favor the possibility of formulating low-friction oils if suitable stable polymeric additives can be found which increase N1 enough to allow lower values to be used. Rheology. (JES)