A new interpretation of isotropic pressure and normal stress in the cone-and-plate, with application to the Oldroyd model

✍ Scribed by M.C. Williams

• Publisher: Elsevier Science
• Year: 1965
• Tongue: English
• Weight: 542 KB
• Volume: 20
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(65)80006-9

✦ Synopsis

An analysis of the steady cone-and-plate shear of a viscoelastic non-Newtonian liquid is presented to show how the isotropic pressurep is related to the elastic normal stresses and inertia of the sample. Critical to the development is a boundary condition of mass conservation, but no rheological model is used and no undetermined constants are necessary.

A consequence is the possibility of finding ~-~v alone, in addition to the function X -----~'~ + ~'¢v --2"rrr always obtained in cone-and-plate work. The ratio W =-----"r,p,p[ X is evaluated from normal stress data on eight polymer solutions over a shear-rate range of 7-1000 see -1, and found to be approximately 1/6 for highly structured liquids. The parameter Wis used to normalize an Oldroyd model, which then has quantitative success in predicting relations between steady-shear and oscillatory-shear stress parameters. This suggests that p =pm may not be the most useful normalizing condition.