Elongation in One Direction

The proportionality factor E, which is constant for small changes of , is the elongation modulus. 

For a viscous material, the deformation continuously changes in time, according to 

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FeS2, 3 2PO). The structure of CaC2 (Section 5.1.2) is similar to that of pyrite, but with elongation in one direction because of alignment of C ions. Intermetallic compounds with the CaC2 structure are listed in Table 9.3. Thus intermetallic compounds can follow the rules for "normal valence" compounds or those of the metallic state. The "normal valence" compounds have lower CN than found in cep or hep structures and are expected to be less "metallic" in terms of electrical conductance, etc. 

We have discussed these structures at this point as examples of structures with similar analytical descriptions. We noted earlier that the PdS2 structure can be described as a pyrites structure which has been elongated in one direction to such... 

The structure is quite different from that of KCg. Instead of every carbon atom bonded to three other carbon atoms, as in graphite and KC, calcium carbide contains discrete C-i ions with carixm-carbon triple bonds. The structure of CaC2 is similar to the Natl structure, but because Cz is a linear anion (not spherical like Cl") the unit cell of CaCl2 is elongated in one direction making the unit cell tetragonal (see Figure 14.14). This carbide is, hence, ionic. 

Keolinite Well formed, six-sided flakes, with a prominent elongation in one direction. 

Fig. 6.63 Seven grains are shown in a two-dimensional hexagonal array before creep deformation. Following diffusion, the grains elongate in one direction and decrease perpendicularly to the tensile axis. A void formation develops between the grains, but grain-boundary sliding, which may accompany this process, removes these voids...

The bulk anisotropy of liquid crystals depends upon the structures of the mesogens, the molecules that form liquid crystalline phases. Not all molecules can form liquid crystalline phases, and the ones that do tend to have certain shapes. More than in most other fields of chemistry, molecular shape rather than the precise nature of the functionality is a key determinant of liquid crystal behavior. Mesogens most often have a significant elongation in one direction (rod-shaped), leading to the common symbolism of an oval, as in Figure 13.7. 

If an isotropic cubical element is elongated in one direction and the dimensional changes in the two mutually perpendicular directions are equal (Fig. 1-14), the experiment is termed simple extension if 7 u is positive, 722 and 733 are equal to each other and negative (or possibly zero). The stresses are tensile stress resulting from the applied force and Pa is the ambient pressure. This type of deformation results when a rod, strip, or fiber is subjected to a tensile force. Equation 42 for this case becomes ... 

So far we have discussed a general deformation. Now consider the specific case of elongation in one direction (x) by a relative amonnt = A (Fig. 2.28). If the volume of the system is assumed to be conserved, then the relative changes in sample dimensions in the y and z directions (kz and A,3 respectively) must both be The cross-sectional area then changes... 

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