Extensional Part Research Articles

Foundations of extensional viscometry Part III: Analysis of combined extensional and squeezing motions in the open-end type hose viscometer

The influence of superposed squeezing upon the radial pressure measured in an open-end type hose viscometer is assessed supposing slow and slightly accelerated motions. An approximate approach on the base of the constitutive equations for the differential type of viscoelastic fluids up to the second total degree is proposed to be indicative of the behavior of a specimen. With the aid of a spatially and temporally constant parameter, namely the transverse contraction ratio of the hose, the entire span from purely axial to purely radial motions of the hose is described. The singularity of purely extensional motions within the lattice of the motion groups considered in Part I becomes discernible. Formulae and diagrams for the purpose of nullifying the inertia and elasticity terms in the measurement pressure are established and lead to a discussion on peculiar viscometric aspects.

Foundations of extensional viscometry part II: Essentials as to design and analysis of hose viscometers

After a historical survey on the evolution of extensional viscometry, two novel types of extensional viscometers are proposed under the designations closed-end and open-end hose viscometer. The hose, which forms an elastically extensible cover of a prolate circular cylinder shape, is to hold an incompressible fluid specimen for investigation, especially under forced oscillations. The measurement of the first type concerns the axial force of the specimen in a thin-walled hose; the measurement of the second type concerns the radial traction of the specimen in a thick-walled hose. Fundamental design features and a mathematical treatment under ideal conditions are set forth for eventually showing how to unroll an informative (though expensive) program of viscometry on the base of harmonic Fourier analysis. In an appendix, the ascertainment of material coefficients is exemplified on specific constitutive assumptions so as to suggest analogously handling other instances on demand.