Explore chapters and articles related to this topic
Flows, Gradients, and Transport Properties
Published in Joel L. Plawsky, Transport Phenomena Fundamentals, 2020
In a flow where the shear rate changes with time, we can have different phenomena. A thixotropic fluid has a viscosity that decreases with time under a sudden applied stress. One can imagine a process of bond breakage occurring where, as time increases, more bonds are broken and so the viscosity decreases. A rheopectic fluid has a viscosity that increases with time under the applied stress. Here we can envision generating entanglements within the fluid making it difficult to move.
Introduction
Published in Steven G. Penoncello, Thermal Energy Systems, 2018
Shear thickening fluids can be classified as rheopectic or dilatant. A rheopectic substance experiences an increase in viscosity over time. Examples of rheopectic fluids include gypsum pastes and printer inks. A dilatant substance experiences an increase in viscosity with an applied shear stress, but it does not change over time. Examples of dilatant fluids include cornstarch paste and silly putty.
Physical Processes
Published in Ralph L. Stephenson, James B. Blackburn, The Industrial Wastewater Systems Handbook, 2018
Ralph L. Stephenson, James B. Blackburn
Some fluids have a time dependent or elastic behavior. Further, some time-dependent fluids break down as a result of applied stress. Such fluids are termed thixotropic. Other fluids show an increase in viscosity with time, and are called rheopectic.
Analysis of selected mechanical parameters for foamed materials with non-Newtonian liquid characteristics in terms of their use in aspects of protective helmets
Published in International Journal of Occupational Safety and Ergonomics, 2020
Marcin Jachowicz, Grzegorz Owczarek
Materials with non-Newtonian liquid characteristics are not subject to Newton’s hydrodynamic law [1]. This means that they fail to demonstrate a linear relationship between the static stress and the compression velocity. Another feature of materials with non-Newtonian liquid characteristics is that they can act like solid bodies, deforming or cracking, or flow like liquids [1]. Materials with non-Newtonian liquid characteristics can take the form of a solid (when they are referred to as foamed materials) or a liquid. Three fundamental groups have been distinguished among the non-Newtonian liquids [1–3]: rheostable liquids, whose rheological properties are independent of the shear time;viscoelastic liquids, combining the rheological properties of viscous liquids and elastic solids, which demonstrate partial elastic return after elimination of the tangential stress that causes deformation –Maxwell fluids and Bingham fluids are particular cases of such liquids;rheologically unstable liquids, whose rheological properties are dependent on the shear time (e.g., thixotropic or rheopectic fluids).
Numerical simulations of adhesive spreading during bonding-induced squeeze
Published in The Journal of Adhesion, 2022
Lorraine Aparecida Silva, Christine Espinosa, Eric Paroissien, Frédéric Lachaud, Lucas F.M. da Silva
The rheology of structural adhesives can be confused sometimes; the variability in viscosity is caused by chemical reactions between the components, so it is not classified as a rheopectic fluid. The rheopectic fluid changes viscosity due to shear stress and the fluid can recover its initial behaviour. In order to determine the rheological behaviour of an adhesive, rheological tests are necessary to measure viscosity during the application of shear stress. Commonly referenced rheologically significant behaviours obtained from experimental squeeze tests are listed in Table 1. Improvements to these models may could be necessary to represent some specific fluid flows in the case of viscoelastic behaviour, for example .[8,26]