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Showing 1 to 20 of 64 for “"oscillatory shear"”.
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Thixotropic-viscoelastic rheological fingerprints in large amplitude oscillatory shear
… work we demonstrate the use of large-amplitude oscillatory shear (LAOS) as a tool to characterize the behavior of constitutive models that exhibit both thixotropic and viscoelastic phenomena. We demonstrate this use of LAOS by first examining the strain controlled LAOS (LAOStrain) response of a …
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Elastic stiffening in PVA-Borax studied with experimental medium amplitude oscillatory shear
… the mechanisms of strain-stiffening and shear-thickening often observed in transient or associative polymer hydrogels; specifically, Poly(vinyl) alcohol (PVA) crosslinked with Sodium tetraborate (Borax), or PVA-Borax. We use medium amplitude oscillatory shear (MAOS) as a tool to measure …
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Oscillatory shear in strain and stress: reduced metrics, first measurements, and linearity limits
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2024-03-01 without embargo terms
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THE YIELDING TRANSITION IN SOFT AMORPHOUS SOLIDS UNDER OSCILLATORY SHEAR: FROM MICROSCOPIC REARRANGEMENTS TO MACROSCOPIC FAILURE
… in amorphous solids. By exploiting a custom shear-cell coupled to a standard bright-field microscope, we provide a unique multiscale analysis of the yielding transition under oscillatory shear overcoming the limitation of conventional rheological measurements. Through a novel acquisition …
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Asymptotically nonliner oscillatory shear: theory, modeling, measurements and applications of nonlinear elasticity to stimuli-responsive composites
… rheological response to mechanical deformation. Oscillatory shear is a popular deformation protocol for viscoelastic characterization, both linear and nonlinear, the latter referred to as large amplitude oscillatory shear (LAOS). However, the accompanying nonlinear material response in LAOS is …
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Instabilities in smectic A liquid crystals
… The behaviour of smectic A liquid crystals under oscillatory shear will be modelled using dynamic continuum theory recently developed by Stewart (2007). The dynamic continuum theory developed by Leslie, Stewart and Nakagawa (1991) is used to model smectic C liquid crystals under the effects of …
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Relaxations in molecularly thin simple liquid films: Linear viscoelasticity and non-linear response to shear
… method was to measure the resistance to applied oscillatory shear deformation as a function of frequency and amplitude of deformation, film thickness and normal pressure using the modified surface forces apparatus technique.
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PMMA Clay Nanocomposites
… transmission electron microscopy (TEM) and oscillatory shear rheology. Morphological studies of the PCN showed that the extent of clay dispersion depended on the clay type. Within the PMMA/Laponite RD nanocomposites an unusual network structure was formed, which appeared to be continuous …
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Dynamics of polymer melts confined between adsorbing surfaces spaced at molecular dimensions
… spaced at molecular dimensions undergoes oscillatory shear. The polymers experience a dynamic liquid-like to rubber-like transition at the onset of long range surface forces $(\sim$4.5 R$\sb{\rm G}).$ The long time relaxations of the polymers are effectively frustrated at the start of the …
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Structure and properties of hydrogen and covalently bonded side group liquid crystalline block copolymers
… and achieved independently via surface epitaxy, oscillatory shear and, for the first time in this class of materials, via magnetic fields. It was found that the morphology adopted by the material under the external fields is strongly dependent on the orientation of the liquid crystalline …
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Designing devices using electro-active yield stress fluids
… rheological measurements from wall-driven shear flows e.g. torsional rheometers and in pressure-driven channel flows, that are more applicable to valve applications. Next, we extend this work by introducing the holding pressure drop and power efficiency as key performance metrics for …
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Rheometry and direct flow observations of a model wax-oil system
… sweeps and stress sweeps. Large amplitude oscillatory shear (LAOS) is also used to gain additional insight into the rheology of the model system. The results from the LAOS measurements show that the wax-oil system exhibits a strain stiffening and shear thinning response under oscillatory …
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Constitutive modelling of branched polymer melts in non-linear response
… melts. The first flow types I examine are simple shear flows. In a shear step-strain flow the stress relaxation of branched polymers is observed to be time-strain separable, whereby the relaxation modulus can be separated into the product of separate functions of time and strain. I show that …
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PAA/PEO Comb Polymer Effects on the Rheological Property Evolution in Concentrated Cement Suspensions
A new oscillatory shear technique was developed to probe the rheological property evolution of concentrated cement systems. The rheological property evolution of ordinary and white Portland cement systems were studied in the absence and presence of pure polyelectrolytes and PAA/PEO comb polymers …
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Rheological characterization and modeling of Laponite gels with application to snug-like locomotion
… stress sweep, creep tests, and large amplitude oscillatory shear tests, defined as LAOS. Concentrations of 1%, 2%, 2.5%, 3%, and 4% wt. of Laponite and distilled water solutions were tested. Laponite gels over 1% wt. concentrations were characterized as yield stress materials, as determined by …
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Rheological inferences with uncertainty quantification
… on the asymptotically-nonlinear medium-amplitude oscillatory shear (MAOS) data, the next systematic step after small-amplitude oscillatory shear (SAOS). The first part of this research is composed of new methods development and improvements in current practices for fitting MAOS. We develop a new, …
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PHYSICAL CHEMISTRY OF COLLOIDAL-NANOPARTICLE INTERACTIONS
… as determined by light scattering, steady state shear and small angle oscillatory shear rheology. Tunable rheology was attributed to the physiochemical interactions of disordered fractal microstructures that are formed via spontaneous, non-directional and random complexation. The thermodynamic …
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Development, characterization and applications of magnetorheological fluid based "smart" materials on the macro-to-micro scale
… been systematically characterized under steady shearing, creep and large amplitude oscillatory shear (LAOS) flow conditions. A rheometer fixture for applying nearly uniform magnetic fields up to 0.4 T has been fabricated to measure both steady-state and transient changes in the fluid properties …
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Nonlinear viscoelastic materials : bioinspired applications and new characterization measures
… nonlinear viscoelasticity using large amplitude oscillatory shear (LAOS) deformation. The LAOS protocol spans the 2D parameter space of deformation amplitude and frequency, known as a Pipkin space. Physically meaningful material measures are proposed, corresponding to clearly defined language …
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Rheology of complex fluid films for biological and mechanical adhesive locomotion
… rheology is examined with large amplitude oscillatory shear (LAOS), and analyzed with Lissajous curves, Fourier transform rheology, and a new measure of non-linear elasticity. In addition, pedal mucus is examined with a flexure-based microgap rheometer, which can test the sample at the …
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