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DTSTART;VALUE=DATE:20240924T171500
DTEND;VALUE=DATE:20240924T171500
UID:16573@agenda.unifr.ch
DESCRIPTION:We investigate the mechanical properties of an over-jammed dispersion of \nCarbopol-microgels in propylene glycol. This dispersion belongs to the class of yield \nstress materials, which are materials that are solids when left unperturbed, yet flow \nwhen the shear stress applied exceeds a certain threshold value. \nThe yielding behavior of materials is typically assessed in either steady shear \nexperiments exploring the flow behavior as a function of shear rate or in oscillatory \nstrain experiments exploring the oscillatory stress response as a function of applied \nstrain amplitude. In this work we address the question whether the maximal shear \nrate or the maximal strain experienced during oscillation is the relevant parameter \ngoverning yielding in oscillatory shear experiments. \nOur oscillatory experiments exploring the stress response as a function of strain \namplitude reveal that yielding occurs in an intermediate range of strains between \ntwo strain regimes, in which the stress response is respectively governed by strain \nand strain rate. Beyond a critical strain defining the high strain regime the stress solely \ndepends on the maximum strain rate experienced during oscillation. This is denoted \nby the direct correspondence of the stress values obtained in respectively oscillatory \nand steady shear rate experiments. By contrast, in the regime denoting the low strain \nregime the stress is a sole function of the strain. \nThus, yielding would be governed by both parameters when considering the \nmechanical response. By contrast, an exploration of the restructuring dynamics at \nthe yield point indicates that structural rearrangements are a sole function of the \nstrain. Further adding to the contradiction we find that the dynamics sharply \nincrease at the yield point, while the mechanics smoothly evolve across the yielding \ntransition. This may indicate that structural relaxation and stress are not linearly \nrelated.
SUMMARY:Deconvoluting strain and strain rate contributions for yielding in oscillatory shear
CATEGORIES:Soutenance de mémoire/thèse
LOCATION:PER 08\, 0.51\, Chemin du Musée 3\, 1700 Fribourg
URL;VALUE=URI:https://agenda.unifr.ch/e/fr/16573
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