Material characteristics deformation

The energy that powers terrestrial processes is derived primarily from the sun and from the Earth s internal heat production (mostly radioactive decay). Solar energy drives atmospheric motions, ocean circulation (tidal energy is minor), the hydrologic cycle, and photosynthesis. The Earth s internal heat drives convection that is largely manifested at the Earth s surface by the characteristic deformation and volcanism associated with plate tectonics, and by the hotspot volcanism associated with rising plumes of especially hot mantle material. 

The predisposition of a material to deform in a particular manner depends on its lattice structure, in particular whether weakly bonded lattice planes are inherently present. In definite terms, most of the materials cannot be classified distinctly into individual categories. Pharmaceuticals exhibit all three characteristics, with one of them being the predominant response, thus making it difficult to clearly demarcate the property favorable for compressibility. 

Hooke s Law, which states that a proportional relationship exists between stress and strain, usually holds for a viscoelastic material at a small strain. This phenomenon is called linear viscoelasticity (LVE). Within the LVE region, the viscoelastic parameters G and G" remain constant when the amplitude of the applied deformation is changed. Consequently, parameters measured within the LVE region are considered material characteristics at the observation time (frequency). 

The dependence of rf, rf, G, and G" on frequency reflects the ability of macromolecular systems to flow like Newtonian fluids if the experimental time allowed them, feXp = 1 /< , is very large compared to the time that they require to fully respond macromolecularly. This temperature-dependent, material-characteristic time is commonly called the relaxation time, X, although it is actually a relaxation spectrum (7). Conversely, when /exp is very short, that is, co is very high compared to X, the macromolecular system can only respond like an elastic solid, able only to undergo deformation and not flow. In... 

The curves shown in Figs. 1-4 describe the particularly characteristic deformation processes of aminoplastics that are of importance for a correct choice of both the method and regimes of processing the material Under other prescribed... 

The inverse relation of the viscosity N and the diffusivity coefficient K. Materials that deform by some recognizable mechanism have a characteristic length R for that mechanism that is fundamentally geometrical and thus insensitive to small changes in, for example, temperature then heating or other change that increases K is likely to diminish N by about the same factor. 

Degree of atomization dependent on material rheology (deformation flow characteristics)... 

Similar to air velocity, an increase of drying temperature intensified the process of moisture evaporation, but it increased susceptibility of the material to deformations. For bananas, the optimum tanperature was found as 60°C. Besides the layer thickness, tanperature, and air velocity, the drying rate of foamed materials depends mainly on foam characteristics like stability, density, and bnbble size. 

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