摘要:

A Galerkin finite element method is used to solve the extrudate swell problem for both a convected Maxwell fluid, and for a fluid with a nonzero second normal stress difference. Exit pressure calculations are undertaken to investigate the validity of the theoretical formulations relating exit pressures to normal stress differences for these two fluids. For the particular fluids and range of shear stresses considered, the numerical results indicate: (1) The underlying incorrect assumption of viscometric flow to the die exit results in normal stress values which are too high. However, this effect is not significant enough to invalidate exit pressure measurements as a means of estimating normal stresses. (2) The exit pressure theory is sometimes applied using the assumptionPc*=0.5 p(0,L)c(orPc*=Ps*) since Han and co‐workers find experimentally thatPc*=Ps*.We find for the convected Maxwell model(N2/N1=0.0)thatPc*=p(0,L)cwhereas for a model withN2/N1=−0.2,Pc*=0.84 p(0,L)c.Our calculations suggest, at least, that the equivalence (or not) ofPc*andPs*depends onN2/N1.(3) For the convected Maxwell fluid:Pc*/τw=0.35(N1/τw)+0.55for a capillary die,Ps*/τw=0.28(N1/τw)+0.30for a slit die. The latter is in agreement with the slit die results of Reddy and Tanner.

ISSN:0148-6055    

DOI:10.1122/1.549741

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

The adsorption of polyacrylamide (PAAm) on silica particles and its effect on the rheological properties of the suspensions were studied with a coaxial cylinder type rheometer. The following two unique observations are reported: (1) For suspensions prepared with PAAm solution in glycerin, the apparent viscosity of suspensions is lower than that of the medium. From the adsorption experiments, it is concluded that the decrease in polymer concentration in the liquid phase by adsorption is primarily responsible for the decrease in the apparent viscosity of the suspensions. (2) For suspensions prepared with PAAm solutions in glycerin/water mixtures, the apparent viscosity of suspensions irreversibly increases when the critical shear rate is exceeded. Considering that the polymer adsorption is irreversible, this behavior may originate from flocculation by shear‐induced irreversible bridging.

ISSN:0148-6055    

DOI:10.1122/1.549742

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

This article shows that a Weissenberg rheogoniometer can be used successfully to generate transient linear data. Stress growth as well as stress relaxation is discussed. Data are presented involving a 3% solution (by weight) of polyacrylamide (Separan AP‐30) and a 6% solution (by weight) of polyisobutylene (PIB). The relation to some of the recent literature is also covered.

ISSN:0148-6055    

DOI:10.1122/1.549743

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

The orientation distribution function of a dumbbell undergoing rotary Brownian motion (with time constant λ) in steady shear flow and the viscosity and normal stress coefficients are computed by a perturbation expansion in small, dimensionless shear ratesλγ̇.It is found that the series expansions for both the viscosity and the first normal stress coefficient have identical radii of convergence atλγ̇=0.81.By using analytical continuation, the solution was extended toλγ̇=1.5,and compared with established results. Our results agree with earlier perturbation calculations of Kirkwood and Plock (1956), Bird and Warner (1971), and numerical calculations of Stewart and So/rensen (1972).

ISSN:0148-6055    

DOI:10.1122/1.549744

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

A constitutive equation describing the orientation‐strain behavior of the hard segments of a polyurethane elastomer is developed. The orientation functions of the hard and soft chain segments of the polyurethane, as determined by infrared dichroism, are shown to be simply related to each other and the tensile strain by assuming that the hard and soft segments act in series under load. A model for the irreversible changes in orientation of the hard segments with strain is constructed based on a distribution of hard elements, all with the same orientation‐strain behavior, but with different yield strains at which orientation may begin. The strain history dependence of the orientation function is of the permanent memory type and is described by Lebesgue norms of the strain. The model is developed for both time‐independent and time‐dependent orientation and predicts the observed hysteresis and time dependence in stress relaxation of the hard‐segment orientation. The soft‐chain‐segment orientation may then be predicted using the series model.

ISSN:0148-6055    

DOI:10.1122/1.549745

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

Calculations are presented of the error, due to variation of shear rate across the gap between the cylinders, encountered when testing non‐Newtonian fluids with concentric cylinder rotational viscometers. Guidelines are given for the interpretation of uncorrected data.

ISSN:0148-6055    

DOI:10.1122/1.549746

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

摘要:

The mechanical properties of iron‐epoxy particulate composites were studied from the glasslike state through the transition region to the rubberlike state in dynamic loading applied by a Dynastat and a Dynalizer apparatus. The effect of filler content on the viscoelastic properties was studied by using six distinct filler concentrations. Measurements were carried out at frequencies between 0.1 and 100 Hz and temperatures from 50 to 120 °C. Composite curves for both the storage and the loss moduli along a wide frequency range were made by applying the time‐temperature super‐position principle. Moreover, the Takayanagi model was used for the prediction of the filler contribution on the storage compliance(D′)in the transition region. Finally, the effect of filler content on the relaxation spectraHand the glass transition temperature was examined.

ISSN:0148-6055    

DOI:10.1122/1.549747

出版商:The Society of Rheology    

年代:1984

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549780

出版商:The Society of Rheology    

年代:1984

数据来源: AIP