Journal ArticleDOI
Measuring yield stress : a new, practical, and precise technique derived from detailed penetrometry analysis
Jalila Boujlel,Philippe Coussot +1 more
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In this paper, the authors studied the force vs depth variations during the progressive penetration of a plate or a cylinder in a bath of simple yield stress fluids with negligible thixotropic character (Carbopol solutions, emulsions, and foams).Abstract:
The displacement of an object through a yield stress is a complex process which involves the continuous deformation and transition of new regions from the solid to the liquid regime. We studied the force vs depth variations during the progressive penetration of a plate or a cylinder in a bath of simple yield stress fluids with negligible thixotropic character (Carbopol solutions, emulsions, and foams). Three regimes could be distinguished: elastic deformation, penetration (partially immersed object), and displacement through the fluid (fully immersed object). A detailed analysis of the force vs depth curves makes it possible to show that in the partially immersed regime the force is the sum of the critical force before penetration and a term associated with a uniform shear stress along the main plate surface, which is independent on the object geometry (plate dimensions and cylinder radius). This understanding can be used to precisely determine the yield stress as the critical shear stress along the plate at vanishing velocities. We also show that it is possible to measure accurately the yield stress from relaxation tests (stress vs time curve for motion stoppage): it indeed appears that the additional force term associated with penetration is negligible in that case so that the asymptotic average shear stress after stoppage is equal to the yield stress.read more
Citations
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The yielding and the linear-to-nonlinear viscoelastic transition of an elastoviscoplastic material
TL;DR: In this article, a commercial hair gel, which is an elastoviscoplastic material, was tested in two rotational rheometers in order to evaluate these two transition points.
Journal ArticleDOI
Measuring the surface tension of yield stress fluids
Jalila Boujlel,Philippe Coussot +1 more
TL;DR: In this paper, the impact of capillary forces on the flow of yield stress fluids was investigated and it was shown that the ratio of this force to the blade perimeter provides the surface tension of the yield stress fluid in the limit of a low (≪1) capillary number.
Journal ArticleDOI
Power-law creep and residual stresses in a carbopol gel
TL;DR: In this article, the interplay between creep and residual stresses in a carbopol microgel was investigated and it was shown that when applied shear stresses lower than some typical value, the microgel experiences a more complex, anomalous creep behavior, characterized by an initial decrease of the strain, that they attribute to the existence of residual stresses of the order of σcffff c that persist after a rest time under a zero shear rate following preshear.
Journal ArticleDOI
Time-resolved dynamics of the yielding transition in soft materials
TL;DR: In this article, a rigorously defined method that maps and quantifies the time-resolved dynamical yielding process of elastoviscoplastic materials is proposed and investigated.
Journal ArticleDOI
Power-law creep and residual stresses in a carbopol microgel
TL;DR: In this paper, the interplay between creep and residual stresses in a carbopol microgel was investigated and it was shown that when applied shear stresses lower than some typical value, the microgel experiences a more complex, anomalous creep behaviour, characterized by an initial decrease of the strain, that they attribute to the existence of residual stresses of the order of σ_\text{c}$ that persist after a rest time under a zero shear rate following preshear.
References
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Book
Food Texture and Viscosity: Concept and Measurement
TL;DR: The TA.XT2 Texture Analyser as discussed by the authors was used to measure texture and Viscosity in the test setup. But it was not a suitable test procedure to evaluate the effect of temperature on texture measurements.
Journal ArticleDOI
Methods of Soil Analysis. Part 4. Physical Methods
TL;DR: The Methods of Soil Analysis (MSA) as discussed by the authors is the most widely used method for soil analysis and has been widely used in the field of soil analysis, especially in the agricultural domain.
Journal ArticleDOI
Creeping motion of a sphere through a Bingham plastic
TL;DR: In this article, a finite element/Newton method is presented for solving the free-boundary problem composed of the velocity and pressure fields and the yield surfaces for creeping flow, and the accuracy of solutions is ascertained by mesh refinement and by calculation of the integrals corresponding to the maximum and minimum variational principles for the problem.
Book
Rheometry of Pastes, Suspensions, and Granular Materials: Applications in Industry and Environment
TL;DR: In this paper, the authors present a set of techniques for measuring the velocity field in a flow of granular pastes and demonstrate how to apply them to industrial and environmental applications.