Sinusoidal Deformations with Large Amplitudes

For investigations of sinusoidally oscillating deformations outside the range of linear viscoelastic behavior, with large amplitudes, a higher power input is necessary 

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Repeated cycles of extension and retraction at constant rate of strain as described in Section 3 above may be regarded as oscillating deformations with a zigzag strain function. Sinusoidally oscillating deformations with large amplitudes can also be employed to study nonlinear behavior, though in general if the strain is a simple sinusoidal function of time the stress cannot be expected to be so, and vice versa ... 

The oscillatory rheological data are very useful to understand the microstracture of the polymeric material while subjected to deformation in the linear viscoelastic region usually with a small amphmde sinusoidal strain, measuring the resultant sinusoidal stress (Khan et al. 1997). Large amplitude oscillatory strain can also be applied. 

Small-amplitude oscillatory flow is often referred to as dynamic shear flow. Fluid deformation under d)mamic simple shear flow can be described by considering ttie fluid wiflun a small gap dX2 between two large parallel plates of which the upper one undergoes small amplitude oscillations in its own plane with a frequency velocity field within the gap can be given by d , = ydxj but y is not a constant as in steady simple shear. Instead it varies sinusoidally and is given by... 

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