摘要:

A method of modeling the mechanism of swelling and the mechanism of shrinking in porous elastic materials is described. The method involves the introduction of fields of spherically self‐equilibrated force systems. Force systems of this type are called centers of compression or centers of dilation in classical elasticity theory. The mechanisms of swelling and of shrinking are illustrated in the case of homogeneous deformations of a body subjected to no surface tractions and no gravitational force. It is argued that further development of theories of this type must be material specific and mechanism (i.e., swelling or shrinking) specific.

ISSN:0148-6055    

DOI:10.1122/1.549787

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

摘要:

A rheological model of the flow of an aqueous electrolyte solution near a polar interface is presented, which is based on general equations of electrostatics and mechanics of an isotropic inhomogeneous continuum. The main purpose of the theory is to account for the consequences of an additional orientation of water molecules caused by the electrical fields of the double layer. Equations of the rheological model are merged with a modified Poisson‐Boltzmann equation in which hydration effects and dielectric saturation are included. Results of a numerical simulation of the flow of10−5N KClsolution in capillary slits of varying widths between104and 10 nm, with negative surface charge densities assumed to be 6.7, 0.3, and0.13 μC/cm2,under pressure gradients in the range of104to109 Pa/m,are presented and discussed.

ISSN:0148-6055    

DOI:10.1122/1.549813

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

摘要:

The rheological properties of four slurry fuels were studied and a variety of complex flow phenomena was observed. The slurry fuels contained ca. 50% by weight carbon black particles with an average particles size of 0.1 μm. In order to characterize the viscoelastic and plastic properties of the slurry fuels, stress growth and steady‐state experiments were performed over a wide range of shear rates. The slurry fuels were shear thinning under most conditions and were shear thickening at extreme conditions. They exhibited thixotropic behavior, with the degree of thixotropy depending on the specific slurry. Most of slurries had a yield stress ranging from 2 to110 dyn/cm2.For the slurries which had a large yield stress, stress overshoot was observed. The stress overshoot increased with increasing shear rate. The maximum stress overshoot occurred at lower shear strains, the higher the shear rate. Temperature effects on the shear viscosity and yield stress were also studied. An unusual temperature dependency was found for one slurry and can be explained as a result of structural formation. A preliminary analysis was developed by using a modification of our kinetic‐elastic theory to describe the pseudoplastic and thixotropic behaviors of materials that exhibit a yield stress. The temperature effect on viscosity was also analyzed in terms of this model.

ISSN:0148-6055    

DOI:10.1122/1.549814

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

摘要:

Rheological properties of disperse systems of photosensitive particles were studied in relation to the degree of aggregation of dispersing particles. Photosensitive particles were prepared by introducing cinnamoyl groups to styrenedivinylbenzene copolymer spherical particles. The degree of aggregation (total number of primary particles forming an aggregate) was controlled by irradiation of light to the disperse system and was estimated from light scattering by assuming a hexagonal close‐packed aggregate model. Viscoelastic properties of the disperse systems of the photosensitive particles in diethylphthalate were measured by means of a cone‐plate type rheometer. Terminal zone of the modulus shifts progressively to lower frequency with increasing the irradiation time, i.e., with increasing the degree of aggregation. It is strongly suggested that the aggregate is a cause of the long‐time relaxation and that the maximum relaxation time of the disperse system can be directly related to the rotational diffusion of the aggregate.

ISSN:0148-6055    

DOI:10.1122/1.549815

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

摘要:

A precision fiber‐spinning apparatus using a suction device to supply the stretching force is used to extend dilute solutions of xanthan gum in a mixture of glycerine and water. Large values of the apparent extensional viscosity are observed for polymer concentrations of 300, 400, and 500 ppm and these tend to a stretch rate independent limit as the fluid residence time on the spinline approaches the reciprocal of the stretch rate. It is shown that polymer‐polymer interactions exist even at these low concentrations, and this precludes the application of the noninteracting multiple bead‐rigid spring theories to the system at hand. Good agreement between experiment and theory, however, is obtained when comparisons are made with the close particle treatment of Batchelor. Based on this, a Trouton ratio in excess of one hundred is predicted for the flow of aqueous xanthan gum solutions in a porous medium with obvious implications for enhanced oil recovery.

ISSN:0148-6055    

DOI:10.1122/1.549788

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

摘要:

A novel technique for measuring viscosity at high shear rates is described. The technique is an extension of a well‐established method, parallel‐disk viscometry, which has been limited traditionally to low shear rates(50,000 s−1)to be attained without disrupting the torsional flow field, and thus controlled measurements of viscosity could be made at those shear rates. The presence of flow disturbances such as shear heating, surface fracture, and radial migration, common impediments in high‐shear measurements, can be readily detected with a thixotropic loop program, and the effect of such disturbances can be separated from the actual rheological response of the fluid. Data are presented on some well‐defined fluids, both Newtonian and shear‐thinning, and the limitations of this technique are discussed.

ISSN:0148-6055    

DOI:10.1122/1.549828

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549837

出版商:The Society of Rheology    

年代:1985

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549839

出版商:The Society of Rheology    

年代:1985

数据来源: AIP