摘要:

An energy approach based on minimum entropy production has been taken in the analysis of the interface shape of vertical bicomponent flow of power‐law fluids. The sheath‐core and single flat interface configurations have been examined for the slit flow geometry in detail. Numerical calculation shows for similar materials of unequal Newtonian viscosities the sheath‐core configuration has a lower rate of entropy production subject to the appropriate constraint. The analysis is also outlined in considerable detail for the cylindrical tube case. The effect of different surface tensions is also examined for the nonflow situation.

ISSN:0148-6055    

DOI:10.1122/1.549301

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

A simple expression has been found relating the relaxation spectrum and nonlinear shear rate dependent viscosity. In this expression the value of the relaxation spectrum is the product of one‐half the shear stress and the slope of the steady flow curve at a relaxation time twice the value of the inverse shear rate. This relation was applied to a set of linear polyethylene melts and found to agree quite well with relaxation spectra obtained from linear viscoelastic quantities. A comparison with a similar equation relating the relaxation spectrum with loss modulus was shown to lead to a transformation between steady‐state viscosity and dynamic viscosity. Similar relations have been found in the literature.

ISSN:0148-6055    

DOI:10.1122/1.549302

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

Suspensions of hardened human red blood cells (RBC) in normal plasma and in isotonic saline were investigated. A suspension of hardened RBC in isotonic saline is Newtonian at low shear rates and concentrations but slightly dilatant at high shear rates and concentrations. The average concentration inside a 99 μ capillary tube(D/d=12.3)is only about 85% of the concentration in the feed reservoir. The flow properties of a suspension of hardened RBC in saline flowing through a 99 μ tube can be predicted from a knowledge of the actual tube concentration and the flow properties obtained in very large tubes. The results found were compared to data for rigid sphere suspensions flowing through tubes about one order of magnitude larger than the sphere diameter.

ISSN:0148-6055    

DOI:10.1122/1.549303

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

Highly filled rubbers undergo both chemical and physical changes during aging. The most commonly observed changes during ambient aging are in: (1) polymer network structure, (2) gel fraction of the binder, and (3) volumetric loading of solids. A quantitative relationship for the modulus change due to the above factors is developed as follows:Es/Er=(νs/νr)⋅(vs/vr)2⋅[(1−φr)/(1−φs)]3whereEis the Young's modulus of the composite, ν is the crosslink density expressed in moles effective chains per cubic centimeter,vis the gel fraction of the binder, φ is the volume filler fraction of the composite, and subscriptsandrrefer to test specimen and reference material, respectively. Two experiments were performed to evaluate the above relationship: experiment A involved the evaluation of various environmental exposures on thin samples of polybutadiene rubber containing about 76 volume percent solid. Weight loss, swelling ratios, and uniaxial tensile properties were measured. Experiment B involved measurement of the gradient of properties adjacent to the interface between the same filled polybutadiene rubber and lowly filled rubber substrate. Swelling ratios, organic extractables, and uniaxial properties were obtained from thin sections cut from a bulk sample after 18 months storage at 80°F. The experimental data from these studies are used to calculate the reduced modulus,Es/Er,using the above equation. The calculated values agree well with the measured values indicating that the change of modulus is a function of approximately the fifth power of the change in the plasticizer content and approximately the first power of the crosslink density.

ISSN:0148-6055    

DOI:10.1122/1.549326

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

Velocity lag between the two discs in the eccentric disc rheometer is determined analytically for a Newtonian fluid, the second order fluid, and for general simple fluids when the offset and slip are small. It is established that the normal thrust between the discs does not measure the second normal stress difference. Experimental measurements of the velocity lag are in good agreement with the analytical expressions which are developed. The influence of the velocity lag on the forces exerted on the free disc is predicted. Experimental results with two different edge geometries indicate the strong influence of edge effects on the forces exerted on the free disc. The correct relationship between the fluid viscosity and the measured forces, therefore, may require detailed analysis of the flow situation in the edge region or careful experimental extrapolation procedures.

ISSN:0148-6055    

DOI:10.1122/1.549322

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

The elimbing effect that occurs when a non‐Newtonian fluid is sheared between rotating concentric cylinders is investigated in detail. A theoretical foundation is established for directly relating the climbing phenomenon to the material functions of a simple fluid. A relationship is developed between the normal stress functions and experimentally measurable quantities associated with the free surface thereby permitting all three material functions to be determined from a study of the flow field in a concentric cylinder apparatus. As an experimental verification of the theory, the material functions of a solution of polyisobutylene in cetane were determined for shear rates between 4 and30 sec−1.A good comparison is obtained between these and other published results for this material.

ISSN:0148-6055    

DOI:10.1122/1.549304

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

Constitutive equations have been formulated for the mechanical behavior of isotropic, elastic materials that dewet. This has been accomplished in part through an application of the stability postulate of Drucker, the implications of which underlie most of the fundamental results of the classical inviscid theory of plasticity. From a phenomenological viewpoint, the two theories differ in the nature of unloading, their dilation behavior, and the form taken by the de‐wetting criterion, which is analogous in the present theory to the yield criterion in plasticity.

ISSN:0148-6055    

DOI:10.1122/1.549305

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

The kinematics and the principal stress difference were determined for a 5% solution of polyisobutylene in mineral oil undergoing plane stagnation flow. These results were then used to evaluate four constitutive equations. The stagnation flow data were obtained for flow into a “T” shaped channel with measurements taken along the centerline. The kinematics consisted of the velocity distribution, and they confirmed the presence of a stagnant zone in which there was no downward flow. The velocity and position data, in a reduced form, were found to superimpose for several flow rates so that a master curve could be used with the constitutive equations to predict the stress differences. The latter were then compared with stress differences determined using a stress‐birefringence apparatus constructed for this purpose. The experimental stress difference along the centerline went through a maximum when plotted against position. The following constitutive equations were evaluated: the White‐Metzner, the Oldroyd 3‐constant, the BKZ, and the WJFLMB equations. The rheological parameters in these equations were obtained using stress‐birefringence data for steady shear flow through a rectangular channel. Each of the equations correctly predicted a delayed normal stress difference growth as a function of time. The WJFLMB model was found unsatisfactory in its ability to predict the magnitude of the stress difference. All the remaining models did a reasonably good job in their predictions with the Oldroyd model being slightly superior at high deformation rates.

ISSN:0148-6055    

DOI:10.1122/1.549323

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

A microstructure model of polymer rheology is applied to study the behavior of the dynamic viscosities under superposed in‐line and transverse oscillations. A general solution valid to first order in oscillatory shear rate is obtained, and the limiting cases of small and large values of the frequency of oscillation are examined. The results for these limiting cases are found to be in agreement with results based on the incompressible BKZ and simple fluid models. A solution valid to third order in oscillatory shear rate is obtained, and for this case the shear stress response is found to contain harmonics of the driving frequency.

ISSN:0148-6055    

DOI:10.1122/1.549306

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

Parallel superposed flow data are presented for four widely studied solutions, three Aroclor solutions of nearly monodisperse polystyrene and a polyisobutylene in Primol solution. Predictions of two integral models, the Bird‐Carreau model and the modified OWFS model, are given and found to describe the data quite well. The experimental results are similar to those of other investigators except that they do not support the relationω0≈0.5γ̇proposed by Booij whereω0is the frequency at which the phase shift is 90°.

ISSN:0148-6055    

DOI:10.1122/1.549307

出版商:The Society of Rheology    

年代:1973

数据来源: AIP