摘要:

Viscous and elastic rheological properties of three very dilute solutions (100 to 500 parts per million) of a polyacrylamide in distilled water which exhibit drag reduction in turbulent flow were determined. Apparent viscosity and first normal stress difference functions were determined using a Weissenberg rheogoniometer over a shear rate range of approximately10−2–1500 sec−1.In addition, transient response characteristics were determined using a specially designed transient rheometer modified for increased resolution. A relatively simple five‐parameter nonlinear integral constitutive equation which was consistent with all steady and unsteady measurements was used to correlate the data. For comparison, Carreau's seven‐parameter model B, which has previously been found to be appropriate for such solutions, was also evaluated for its ability to represent the observed data. Although capable of a precise representation of the steady shear and normal stress data, this model is incapable of qualitative representation of the transient response properties. The results indicate that, as expected, the viscous properties have less influence on the transient response than on the steady shear response.

ISSN:0148-6055    

DOI:10.1122/1.549480

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

摘要:

A set of constitutive equations has been developed to represent nonlinear anelastic behavior, i.e., energy losses and rate‐dependent moduli for geometrically large, reversible deformations. These equations are in incremental form and can be used to solve boundary value problems by numerical methods. Two problems were considered: thick‐walled spheres subjected to cycles of internal pressure, and a long rod subjected to imposed axial velocity (the simple tension test). Experiments were carried out for both conditions on specimens made of a synthetic rubber at three different temperatures (each under isothermal conditions) and over two decades of loading rates. Response curves were calculated based on the constitutive equations and chosen values of the material constants. Generally good agreement was obtained between the predicted and experimental results.

ISSN:0148-6055    

DOI:10.1122/1.549478

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

摘要:

A nonlinear constitutive equation for polymer melts and concentrated solutions is derived from a Lodge‐Yamamoto type of network theory. The network junctions are postulated to move nonaffinely in a well‐defined manner. The functional form of the creation and destruction rates of junctions is assumed to depend on the average extension of the network strand and the absolute temperature in such a way to allow for the time‐temperature superposition principle. The theory shows good agreement with all data examined. The paper concludes with a strong flow problem (melt spinning). The results indicate the validity of the model in this flow regime.

ISSN:0148-6055    

DOI:10.1122/1.549481

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549496

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549502

出版商:The Society of Rheology    

年代:1978

数据来源: AIP