摘要:

The advantages of using the hybrid methods for calculation of the relaxation spectrum are demonstrated. A starting point for the numerical method is one of the higher approximations of relaxation spectrum due to Schwarzl and Staverman, Fujita, Ferry and Ninomiya, and Tschoegl. The corresponding kernel functions are generally “well posed”. Further improvement in the determination of relaxation spectrum may be achieved when a suitable numerical method is used. A sample calculation for a wide spectrum and Rouse distribution of relaxation times is presented.

ISSN:0148-6055    

DOI:10.1122/1.549316

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

It has been shown that the sign and magnitude, of the Weissenberg effect in a viscoelastic liquid depends on the method of observation, namely, through the shape of the free surface or through the height difference of radial tappings. The Oldroyd A and the Walters A′ fluids display the negative Weissenberg effect as far as the free surface is concerned, but they display the positive effect in radial tappings. The Oldroyd B as well as the Walters B′ fluid display identical positive effect in both types of observations. The second order fluid displays the positive effect in radial tappings, but may display either effect when the free surface is observed.

ISSN:0148-6055    

DOI:10.1122/1.549284

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

The dynamic viscoelastic properties of semisolid emulsions (commercial cosmetic creams) at 25°C were measured by means of a Weissenberg rheogoniometer at frequencies ranging from1.582×10−3to 1.582 Hz. In general, these emulsions manifested remarkable nonlinear viscoelasticity even at very small strains; when sinusoidal strains were applied to the emulsions, the resultant stresses were not sinusoidal, in marked contrast to the case in ordinary linear viscoelastic materials. Such nonsinusoidal stresses were analyzed by the method proposed by Onogi et al. to give nonlinear viscoelastic functions. The frequency dependences of these nonlinear functions for the emulsions were quite different from those of the viscoelastic functions for polymer solutions or melts, especially in the low frequency range; the viscoelastic functions for the semisolid emulsions showed second plateaus lower than the so‐called rubbery plateau. Some considerations concerning the origin of the nonsinusoidal stresses were given, and it was concluded that the origin was the dynamic yield stress which was originated from the structure in the semisolid emulsions.

ISSN:0148-6055    

DOI:10.1122/1.549285

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

摘要:

A survey of normal stress measurements for polyisobutylene fluids is made. The first normal stress(N1)data are correlated withN1c2/τ2as a very weak function of concentration (c), molecular weight (M), and shear stress (τ). We also find the second normal stress as about −0.15 ofN1.The limitations of this empirical correlation are discussed.

ISSN:0148-6055    

DOI:10.1122/1.549317

出版商:The Society of Rheology    

年代:1973

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549318

出版商:The Society of Rheology    

年代:1973

数据来源: AIP