Large amplitude oscillatory shear LAOS

Jeyaseelan and Giacomin (1995) examine the use of large-amplitude oscillatory-shear (LAOS) rheology of filled polymer melts (HDPE filled with carbon black) and use transient-network theory (which separates filler and polymer entanglement effects) to describe the non-linear flow behaviour. 

Shear flow fields are a remarkably effective means of orienting copol5mier microdomains. Large amplitude oscillatory shear (LAOS) and extrusion are common methods used to align... 

K. Hyun, S. Hoefl, S. Kahle, and M. Wilhelm. Polymer motion as detected via dielectric spectra of l,4-c -polyisoprene under large amplitude oscillatory shear (LAOS). J. Non-Newtonian Fluid Mech., 160 (2009), 93-103. 

Large amplitude oscillatory shear (LAOS) stress data in the time domain can be analyzed using the well established FT-rheology protocols [21, 44]. LAOS measurements impose a sinusoidal deformation of y t) =yosin coit), where... 

In this chapter we report several applications of large amplitude oscillatory shear (LAOS) to colloidal systems. LAOS is a technique that can induce structural changes in soft matter systems and was used here to characterize dilute emulsions, glassy suspensions and a colloidal nanoemulsion gel beyond the linear viscoelastic regime. 

We have carried out standard rheometric tests as done many times in the literature for entangled polymer solutions. These experiments include startup shear, large amplitude oscillatory shear (LAOS) and large step strain. In terms of the rheological features, we observed the same as others. For example, there is a stress overshoot in startup shear in the stress plateau region the apparent G can drop below G" at frequencies of the elastic plateau and amplitudes around and above 100% and relaxation modulus decreases in time after large step strains. 

As an extension of the dynamic test in the linear regime, a large-amplitude oscillatory shear (LAOS), y(t) = /o sin or, is often applied to a material to measure the oscillating shear stress (Ts (and sometimes the first normal stress difference, too). In the stationary state, cTs under LAOS is contributed not only from the fundamental harmonics (oscillating at the angular frequency of strain, cu) but also from the higher order (mostly odd) harmonics and can be expressed as... 

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