摘要:

Solutions to the equation of motion have been obtained for a viscoelastic fluid which obeys an Oldroyd three‐constant constitutive equation. The solutions apply to a fluid at rest which at zero time is subjected to (1) a step change in pressure gradient or (2) a sinusoidally varying pressure gradient. From these results one can predict the response of the fluid to an arbitrary time‐dependent pressure gradient. Curves are presented which show how the flow of a viscoelastic fluid, when subjected to a step change in pressure, can overshoot the final steady‐state flow. Amplitude and phase relationships between different variables are presented for a sinusoidally varying pressure gradient. Comparisons are made with available experimental data.

ISSN:0148-6055    

DOI:10.1122/1.549027

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

In the work reported here the transition from laminar to nonlaminar flow was investigated as a function of volume fraction of the dispersed phase for a number of synthetic latices. Two instruments, a conicylindrical viscometer and a high pressure capillary viscometer, were used but Reynolds numbers were calculated only with the capillary instrument. It was found that the use of a dispersion viscosity gives a Reynolds number which decreases with increasing volume fraction. However, if one uses the viscosity of the continuous medium, i.e., water, the Reynolds number apparently increases or remains constant. This result is very similar to some results reported on the laminar‐to‐turbulent transition for solutions of poly(acrylic acid) in water.

ISSN:0148-6055    

DOI:10.1122/1.549028

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

An expression for the modulus of rigidity of an elastic material in which a rigid filler is dispersed is extended to deal with a viscoelastic matrix. It is shown that the introduction of the filler adds a second relaxation (or retardation) time to that of the matrix.

ISSN:0148-6055    

DOI:10.1122/1.549004

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

A constitutive equation of deformable media subjected to infinitesimal deformation is derived from the principles of thermodynamics. An explicit equation, which contains physical nonlinearity, is formulated by using the invariant properties of isotropic media. It is found that the equation provides a consistent description of creep and stress relaxation.

ISSN:0148-6055    

DOI:10.1122/1.549029

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

A study was made of the flow patterns in a capillary rheometer barrel to determine if there were any phenomena which might affect viscosity determinations. The rheometer barrel was loaded with layer of several different colors of the same plastic. Various percentages of the initial charge were extruded through the capillary using normal techniques at various shear rates and temperatures. At the end of each test, the material remaining in the barrel was frozen and removed as a plug. The plugs were then sectioned and a flow diagram was constructed by measuring the colored layers. Although the expected laminar flow was observed, upward flow at the wall and channeling at the center were also evident. These phenomena were noted even when only a small portion of the charge had been extruded through the capillary. This paper presents these findings in detail, picturing the flow patterns observed and illustrating the effects of temperature and shear rate.

ISSN:0148-6055    

DOI:10.1122/1.549005

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549030

出版商:The Society of Rheology    

年代:1965

数据来源: AIP