Derivation of Viscoelastic Constants

In principle, viscoelastic constants can be extracted from the experimental data by fitting Eq. 70 (or any of the more complicated equations below) to the data. For a small film fhickness, certain approximations hold which make the derivation more transparent. If kfdf is much less than unity, the tangent in Eq. 70 can be Taylor-expanded to third order as tan(x) l/3x, resulting 

In standard polymer rheology, there are no inertial effects and is always negative [72]. The choice of the exponents and does affect the derived values of the compliance. Generally speaking, viscoelastic dispersion applies to all viscoelastic parameters, not just the compliance of the film. However, for the crystal and the electrodes, the viscoelastic dispersion is often weaker than for polymer films. 

Electrode effects are very important in the determination offrom experimental data (Fig. 11). Unless the electrode thickness is precisely known, the derivation of is difficult. The viscous compliance, Jf, can be derived much 

The Voigt modes is represented by Fig. 8 if the spring on the right-hand side is omitted. Omission of the spring is dangerous because it leads to an infinite stiffness at infinite frequencies. The Voigt model only makes sense in the low-frequency hmit. 

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