Processes occurring during deformation

Fig. 10 Schematic representation of processes occurring during deformation and recovery on the molecular level (a) neat polymer chains, (b) nanocomposite chains, the lines refer to the exfoliated layer silicates. Reprinted from [105]. Copyright 2007, with permission from Elsevier...

In contrast to the processes commonly considered in electrochemistry, electrochemical processes occur during friction under conditions of moving and deforming discrete contacts of individual microasperities. The participation of electrolytes as a liquid layer in the friction pair leads to potential leaps of 9 3 and 933 the metal-solution interface and to the contact potential difference 9 2 ill metal contacts (see Fig. 1.7) [22]. As a result, a short-circuited galvanic microelement appears with a probability of redox reactions on its electrodes. 

Time-dependent behavior of soil occurs during deformation and shear failure can be described as a rate process. The theory of absolute reaction rates was developed by Gladstone, Laidler, and Eyring (1941). Application of this theory to the problem of soil creep of soils has been studied by a number of authors Murayama and Shibata (1964) Christensen and Wu (1964) Mitchell (1964) Mitchell, Campanella, and Singh (1968) Keedwell (1984) Feda (1989) and Kuhn and Mitchell (1992). 

A small hysteresis between tensile loading and unloading curves was detected. The total strain is regained. Those processes are defined as anelastic ones. A temperature change occurs during deformation (adiabatic process). Thus, anelastic processes should depend on the strain rate, e, but this was not found in the experiment. This point cannot be explained. 

The surfactant plays many roles, one of which is lowering interfacial tension, hence p, hence the stress needed to deform and break up a droplet. It is essential that the surfactant prevents coalescence of newly formed drops. The various processes occurring during emulsification, i.e. droplet break-up, adsorption of surfactant and droplet collisions (which may or may not lead to coalescence), are illustrated in Figure 2.2. Typically, each of these processes occurs numerous times during emulsification, and the timescale for each step is very small, for instance a microsecond. 

As previously stated, molecular orientation occurs during melt processing of polymers. On removal of the deforming stresses the molecules start to coil up again but the process may not go to equilibrium before the polymer cools to below its Tg. This leads to residual orientation (frozen-in strain) and corresponding frozen-in stresses. 

The physical processes that occur during indentation are schematically illustrated in Fig. 31. As the indenter is driven into the material, both elastic and plastic deformation occurs, which results in the formation of a hardness impression conforming to the shape of the indenter to some contact depth, h. During indenter withdrawal, only the elastic portion of the displacement is recovered, which facilitates the use of elastic solutions in modeling the contact process. 

Early descriptions of the changes in cytoplasmic structure that occurred during pseudopodia formation referred to a soluble (Sol) and a gelled or semisolid (Gel) state. Thus, it was assumed that the cytoplasm in the organelle-free peripheral cytoplasm was in the Sol state, whilst in pseudopodia (which resist deformation by mechanical forces) it is in the Gel state. Thus, the control of neutrophil functions via changes in cytoplasmic structure may be explained by understanding this so-called Sol —> Gel transition. It is perhaps more convenient to think of this transition as the processes that elongate and cross-link actin filaments. 

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