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The stress state of elastic fluids in viscometric flow
Author(s) -
Miller M. J.,
Christiansen E. B.
Publication year - 1972
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690180321
Subject(s) - shear stress , shear rate , shearing (physics) , mechanics , rheology , normal force , stress (linguistics) , materials science , geometry , chemistry , mathematics , composite material , physics , linguistics , philosophy
A new method of instrumentation for normal‐stress determinations was developed, making possible accurate unsteady state as well as steady state measurements, eliminating errors arising from fluid‐filled pressure‐tap holes, and permitting the determination of the complete stress state in a single cone‐and‐plate shearing‐geometry experiment. Sensitive, nonflow semiconductor pressure transducers mounted at several radial positions with their pressuresensing diaphragms flush with the plate surface provide data for the normal‐stress distribution. The normal‐stress distribution, together with the total normal force from the single‐geometry experiment, enables determination of the primary and secondary normal‐stress differences by two independent methods of analysis while the transmitted torque enables determination of the viscosity, each as a function of shear rate. Only the normal‐stress distribution is required if an independent check on the normal‐stress determination is not desired. Similar advantages arise in the application of the instrumentation to a parallel‐plate shearing geometry, The new instrumentation was used in the determination of the complete rheological stress state of three aqueous and two “Tetralin” solutions of polymers in a cone‐and‐plate shearing geometry shear rates of 0.02 to 450 s −1 on a Model R‐17 Weissenberg Rheogoniometer. The normalstress differences computed by means of two methods of analysis are in surprisingly good agreement. The ratio of the secondary to the primary normal‐stress difference was negative. The absolute values of this ratio decreased with increases in the shear rate, the maximum observed value being 0.4.