Oscillatory and Steady-State Shear

If a viscoelastic liquid is subjected to steady-state shear at a constant rate 721 and superimposed on this is an oscillatory shear of small maximum amplitude 721 (in the parallel direction) or 723 (in the transverse direction), the dynamic storage and loss moduli are found to be dependent on 721. The geometry is illustrated in Fig. 17-38 a systematic discussion of these phenomena has been given by Mar-kovitz 2 and Walters.  

Geometry for combined steady state shear with oscillating shear in parallel and transverse 

The effect of steady-state shear on the oscillating normal stresses produced by parallel oscillating shear deformations has also been studied by Booij. Whereas, in the absence of steady shear, the oscillatory component of the normal stress has twice the frequency of the shear strain in accordance with equation 76 of Chapter 3, with increasing steady shear a component with the same frequency develops and eventually dominates. The storage and loss components of the complex normal stress depend on frequency in a complicated manner. 

Small oscillating deformations transverse to steady-state shear have been studied by Simmons, with results which also correspond qualitatively to the progressive disappearance of mechanisms with the longest relaxation times as the steady shear rate is increased. 

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The extended Cox-Merz rule [49] can be successfully applied for HD and LLD. This nile states that the viscosity and elasticity coefficients for oscillatory and steady state shear flows are related, according to ... 

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