Mechanical shear, sources

The physical basis for the lamella number is that a combination of capillary suction in the Plateau borders and the influence of mechanical shear cause the oil-phase distortion and pinch off into droplets. This result is in accord with the observations of emulsification and imbibition by Lobo et al. (50), French et al. (54), and Schramm and Novosad (37). The mechanical shear may come from several sources, including the flow... 

Shear yielding is well established as the principal deformation mechanism and source of energy dissipation in both uiunodified and rubbo -toughened epoxy resins [2,3,27,83,121]. As molecular mobility in the epoxy resin network chains decreases, the ability of the matrix to deform by shear yielding is reduced. This is the reason why epoxy resins become both more brittle and more difficult to toughen as the epoxy resin crosslink density increases and/or as the network chains increase in rigidity, e.g. by use of highly aromatic epoxy resin monomers (see Section 19.7.1.1). 

The source mechanism of an idealized shearing source can be described by summing the off-diagonal components, -(A + Myx) of the moment tensor (Fig. 5.18). 

As a result of their diverse architecture, different descriptors such as whiskers, nanowhiskers, cellulose nanocrystals, nano-crystalline cellulose, monocrystals or microcrystallites are used in literature to describe crystalline rod-like nanoparticles (Eichhom et al, 2010 Frone et al, 2011 Khalil et al, 2012), while terms such as microfibrils, microfibrillated cellulose or nanofibrillated cellulose are used to describe cellulosic nanoparticles that are obtained as a result of mechanical shearing disintegration process (Siqueira et al, 2010 Siqueira et al, 2011). In this paper, sources, isolation, property and applications of natural cellulose fibers are reviewed. 

Many studies have been done on isolation and characterization of cellulose nanofibers from various sources. Cellulose nanofibers can be extracted from the cell walls by simple mechanical shearing or by a combination of both chemical and mechanical routes [10]. 

Wear. Ceramics generally exhibit excellent wear properties. Wear is deterrnined by a ceramic s friction and adhesion behavior, and occurs by two mechanisms adhesive wear and abrasive wear (43). Adhesive wear occurs when interfacial adhesion produces a localized Kj when the body on one side of the interface is moved relative to the other. If the strength of either of the materials is lower than the interfacial shear strength, fracture occurs. Lubricants (see Lubricants and lubrication) minimize adhesion between adj acent surfaces by providing an interlayer that shears easily. Abrasive wear occurs when one material is softer than the other. Particles originating in the harder material are introduced into the interface between the two materials and plow into and remove material from the softer material (52). Hard particles from extrinsic sources can also cause abrasive wear, and wear may occur in both of the materials depending on the hardness of the particle. 

Goldberg and Rubin [Ind. Eng. Chem. Proce.s.s Des. Dev., 6 195 (1967)] showed in tests with a disk spinning vertically to the foam layer that most mechanical procedures, whether centrifugation, mixing, or blowing through nozzles, consist basically of the application of shear stress. Subjecting foam to an air-jet impact can also provide a source... 

Quantitative evidence regarding chain entanglements comes from three principal sources, each solidly based in continuum mechanics linear viscoelastic properties, the non-linear properties associated with steady shearing flows, and the equilibrium moduli of crosslinked networks. Data on the effects of molecular structure are most extensive in the case of linear viscoelasticity. The phenomena attributed to chain entanglement are very prominent here, and the linear viscoelastic properties lend themselves most readily to molecular modeling since the configuration of the system is displaced for equilibrium only slightly by the measurement. 

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