Mechanical driving force

As the stress is reduced, the rate of power-law creep (eqn. (19.1)) falls quickly (remember n is between 3 and 8). But creep does not stop instead, an alternative mechanism takes over. As Fig. 19.4 shows, a polycrystal can extend in response to the applied stress, ct, by grain elongation here, cr acts again as a mechanical driving force but, this time atoms diffuse from one set of the grain faces to the other, and dislocations are not involved. At high T/Tm, this diffusion takes place through the crystal itself, that... 

The basic assumptions of fracture mechanics are (1) that the material behaves as a linear elastic isotropic continuum and (2) the crack tip inelastic zone size is small with respect to all other dimensions. Here we will consider the limitations of using the term K = YOpos Ttato describe the mechanical driving force for crack extension of small cracks at values of stress that are high with respect to the elastic limit. 

The utility of K or any elastic plastic fracture mechanics (EPFM) parameter to describe the mechanical driving force for crack growth is based on the ability of that parameter to characterize the stress-strain conditions at the crack tip in a maimer which accounts for a variety of crack lengths, component geometries and loading conditions. Equal values of K should correspond to equal crack tip stress-strain conditions and, consequently, to equivalent crack growth behavior. In such a case we have mechanical similitude. Mechanical similitude implies equivalent crack tip inelastic zones and equivalent elastic stress fields. Fracture mechanics is... 

Of course, depending on the system, the optimum state identified by the second entropy may be the state with zero net transitions, which is just the equilibrium state. So in this sense the nonequilibrium Second Law encompasses Clausius Second Law. The real novelty of the nonequilibrium Second Law is not so much that it deals with the steady state but rather that it invokes the speed of time quantitatively. In this sense it is not restricted to steady-state problems, but can in principle be formulated to include transient and harmonic effects, where the thermodynamic or mechanical driving forces change with time. The concept of transitions in the present law is readily generalized to, for example, transitions between velocity macrostates, which would be called an acceleration, and spontaneous changes in such accelerations would be accompanied by an increase in the corresponding entropy. Even more generally it can be applied to a path of macrostates in time. 

Thus, the collapse of the tetrahedral adduct to the mixed anhydride intermediate is determined purely by rotation around a single C-0 bond of the tetrahedral species formed after substrate binding. The above authors have suggested that the torsional distortion of the substrate by the sites of secondary recognition provides the mechanical driving force that causes the required bond rotation to convert 50 into 51. This interpretation is supported by inspection of molecular models. 

Mass flow is associated with the mechanical driving forces and thermal driving force... 

The rigorous kinetic theory, described in sect. 2.9, shows that the net species relative mass flux in a multi-component mixture will consist of three contributions associated with the mechanical driving forces and an additional contribution associated with the thermal driving force ... 

We emphasize that states in mechanical equilibrium have both the driving force (P -PP) and the volume change (dU ) equal to zero. Moreover, neither isothermal nor adiabatic constant-mass changes in volume can occur without a mechanical driving force that is, we cannot have 0 with P - pP = 0. 

Process Type of Membranes Average Pore Size Separation Mechanism Driving Force... 

Strength needed for the application in chemical processes and for tolerating the down-up pressure difference, which is the hydrogen permeation mechanism driving force. 

A critical research gap in corrosion science is the absence of the corrosion equivalent for the stress intensity factor (K) that has been the mainstay of structural mechanics for the past several decades. The stress intensity factor was developed to predict the behavior of pre-existing flaws in structural materials and the eventual life of a component under conditions in which the flaw develops into stable cracks. The power of K is in the concept of similitude well-defined cracks and crack tips that are different in size or shape but possess the same K (as determined by geometry, loading, and the theories of linear-elastic fracture mechanics) will experience the same mechanical driving force for crack growth. Thus, similitude allows small, well-defined samples to be tested in the laboratory to determine the conditions of crack growth and fracture and the results to be quantitatively extended to more complicated real-world structures containing cracks. Virtually... 

Section 6.1 begins with a description of mechanisms/ driving forces/sources that cause bulk flow to take place in the separation device. Following a brief description of these sources of flow into and out of the separation device, as well as inside the device, we provide a brief illustration of a variety of ways in which the feed is introduced into the separator. Section 6.2 will identify the general equations of change in an open separator. 

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