Energy dissipation, mechanism

The discussion begins below with an overview of proposed energy dissipation mechanisms that lead to friction. This is followed by brief discussions of phenomenological friction laws that describe the dependence of friction upon normal load and sliding velocity. The dependence of friction on the symmetry of the surfaces that are in contact is discussed later. 

Based on the discussion in earlier sections of this chapter, one may expect atomically flat incommensurate surfaces to be superlubric. Indeed the first suggestion that ultra-low friction may be possible was based on simulations of copper surfaces.6,7 Furthermore, the simulations of Ni(100)/(100) interfaces discussed in the previous section showed very low friction when the surfaces were atomically flat and misoriented (see the data for the atomically flat system between 30° and 60° in Figure 21). In general, however, it is reasonable to assume that bare metals are not good candidates for superlubric materials because they are vulnerable to a variety of energy dissipation mechanisms such as dislocation formation, plastic deformation, and wear. 

As shown in Chapter 10, molecular dynamics in polymers is characterized by localised and cooperative motions that are responsible for the existence of different relaxations (a, (3, y). These, in turn, are responsible for energy dissipation, mechanical damping, mechanical transitions and, more generally, of what is called a viscoelastic behavior - intermediary between an elastic solid and a viscous liquid (Ferry, 1961 McCrum et al., 1967). 

Crack bridging by TP particles seems to be the main energy-dissipating mechanism. 

Energy density, free 62-65, 69 Energy dissipation, mechanism 76 Epoxy 129... 

As both referees pointed out, other reasons have been offered for energy dissipation during impact. In each case however some energy dissipating mechanism must be provided. The present work indicates that, at least for the samples used, this mechanism is provided by the dynamic mechanical dissipation factor. This in turn is attributed to the fact that at the high strain rates of impact the linear viscoelastic region is the largest, if not the only, contributor to the dissipation process. 

Recently microporous and mesoporous materials were found to be particularly suitable for a new type of applications in the mechanical field. This paper reports experimental features about the dissipative forced intrusion of water in highly hydrophobic mesoporous materials this phenomenon can be used to develop a new type of dampers and/or actuators. Silica-based materials behavior was investigated. Among them, MCM-41 exhibits original and interesting properties towards the potential developments of dampers and appears to be of great interest for the comprehension of energy dissipation mechanisms. 

Dispersions coefficients were found to lie somewhere in between predictions based, on the low side, the entrainment model, and on the high side the isotropic turbulence model (energy dissipation). From the previous discussion, one is tempted to propose a two-regime model comprised of entrainment and energy dissipation mechanisms ... 

Kysar, J.W. Energy dissipation mechanisms in ductile fracture. J. Mech. Phys. Solids 2003, 51, 795-824. 

This compound has been frequently used as a photochemical stabilizer and the photophysical dynamics is interesting in relation to the efficient energy dissipation mechanism [168, 169], The TG signal from o-HBP in water was fitted well by a superposition of the Dens.G and Temp.G signals. At 4°C, the signal consisted of the pure Temp.G component (Fig. 28). 

Thus, if the number of activator sites increase beyond a specific, but not easily defined, density, then the energy dissipation mechanisms become dominant. 

The first term in Equation 11.11 is the essential work of fracture (We), that is, the work required to create new surfaces in inner fracture surface zone and is surface related. The second term is referred to as nonessential work (Wp). It is associated with various energy dissipation mechanisms that occur in the outer plastic zone and is volume related. Thus, Wf can be written as... 

I. Ohmine,/. Chem. Phys., 85,3342 (1986). Energy Dissipation Mechanism of the Optically Excited Molecules in Solvents A Trajectory Study for a Photoisomerization Process of the TT-Conjugated Molecule in Ar and Water. 

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