摘要:

The periodic squeeze motion of a thin fluid film formed between two parallel planes is considered. The fluid is assumed to exhibit shear dependence and relaxation properties. Analysis shows that a time‐average super‐ or subambient pressure is generated which depends on the ratio of the periods of the compression and expansion strokes. Fluid consistency, shear rate exponent, plate geometry, and stroke affect the magnitude of the pressure values. The relaxation constant of the fluid enters only into the transient and the periodic parts of the squeeze film response. These effects are not obtained for Newtonian fluids or if the compression and expansion periods are equal.

ISSN:0148-6055    

DOI:10.1122/1.549075

出版商:The Society of Rheology    

年代:1967

数据来源: AIP

摘要:

Non‐Newtonian viscosity and the primary normal stress difference in steady simple shear flow and the dynamic viscosity and dynamic storage modulus in oscillatory simple shear flow were measured for three viscoelastic fluids. Most of the data were obtained with a Weissenberg Rheogoniometer. The data were used to evaluate a differential model and two integral models, with all three models predicting the same relations for the material functions. The models satisfactorily describe the non‐Newtonian viscosity, dynamic viscosity, and storage modulus data for each solution, but fail to describe the primary normal stress difference data by predicting incorrect slopes in the “power‐law” regions.

ISSN:0148-6055    

DOI:10.1122/1.549076

出版商:The Society of Rheology    

年代:1967

数据来源: AIP

摘要:

The same three solutions used in Part I were used to measure stress relaxation after the cessation of steady simple shear flow and stress growth after the onset of steady simple shear flow. Both shear and normal stress difference responses were measured. In addition, “interrupted flow,” a turret‐shaped function for the velocity gradient, was studied. The data are used to evaluate the three rheological models considered in Part I. These models all make the same predictions for stress relaxation. They differ markedly in their predictions for stress growth; the OWFS model predicts no overshoot, the WJFLMB model predicts a single overshoot, and the Spriggs 4‐constant model predicts oscillatory behavior. The models satisfactorily describe the stress relaxation data but fail to describe the stress growth data.

ISSN:0148-6055    

DOI:10.1122/1.549077

出版商:The Society of Rheology    

年代:1967

数据来源: AIP

摘要:

As part of a continuing exploration of the mechanical behavior of materials which have temperature‐dependent properties, the effect of a hammer blow on a small sample of model viscoelastic material is considered. In this situation, the duration of the experiment is long compared with the time required for stress equilibrium to develop and short in comparison with the thermal relaxation time of the sample. The analysis shows how a material which responds in an almost perfectly elastic manner to a light blow can respond in a viscous manner to a heavy blow. It also suggests that a homogeneous continuum with properties that would make it acceptable as a structural material must be brittle. This result may contribute to the understanding of the important relationship between microstructure and ductility. The hammer experiment involves relatively high strain rates which vary continuously during the deformation. In earlier work, the constant deformation rate case was studied. The latter situation is difficult to produce in the laboratory in the range of rates of interest here and is less likely to arise in practice.

ISSN:0148-6055    

DOI:10.1122/1.549078

出版商:The Society of Rheology    

年代:1967

数据来源: AIP

摘要:

The melt rheology of poly(vinyl chloride) (PVC) resin has been investigated as a function of shear rate over an 80°C temperature range. The microcrystalline nature of PVC has been observed in the form of a low activation energy(δEγ)Lat low temperatures and a high activation energy(δEγ)Hat high temperatures. The two distinct flow activation energies suggest different rheological flow units in the low and high temperature regions. It was possible to reduce the shear stress‐shear rate curves to a single master curve at 200°C by superposition of temperature and rate of shear.

ISSN:0148-6055    

DOI:10.1122/1.549079

出版商:The Society of Rheology    

年代:1967

数据来源: AIP

摘要:

Biaxial and uniaxial stress relaxation data are used to show that dimethyl siloxane rubber containing 28 wt.‐%SiO2as filler, exhibits, in the presence of large deformation, material behavior which is “viscoelastic” in the sense that it can be described, accurately, by the rheological equations of finite linear viscoelasticity. In particular, a constitutive equation for this material is found which containsthreerelaxation functions all of which are (a) proportional to the same function of time and are (b) independent of the deformation.

ISSN:0148-6055    

DOI:10.1122/1.549080

出版商:The Society of Rheology    

年代:1967

数据来源: AIP