Straining-induced effects

G.E. Pikus, L.G. Bir [Symmetry and Strain-Induced Effects in Semiconductors (Wiley, New York, 1974) ]... 

Schelling, G., Miihlberger, M., Springholz, G. and SchafSer, F. (2001), Sii 3.Gea. growth instabilities on vicinal Si(OOl) substrates Kinetic versus strain-induced effects. Physical Review B 64, 041301-4. 

Symmetry and Strain-Induced Effects in Semiconductors, John Wiley Sons,... 

Studies have considered the effect of crystallinity on the performance of CR adhesives (97), on segmental mobiUty as determined by nqr studies (101), on strain induced property changes (102), and on relaxation processes (103). 

The referential formulation is translated into an equivalent current spatial description in terms of the Cauchy stress tensor and Almansi strain tensor, which have components relative to the current spatial configuration. The spatial constitutive equations take a form similar to the referential equations, but the moduli and elastic limit functions depend on the deformation, showing effects that have misleadingly been called strain-induced hardening and anisotropy. Since the components of spatial tensors change with relative rigid rotation between the coordinate frame and the material, it is relatively difficult to construct specific constitutive functions to represent particular materials. 

The deformation may be viewed as composed of a pure stretch followed by a rigid rotation. Stress and strain tensors may be defined whose components are referred to an intermediate stretched but unrotated spatial configuration. The referential formulation may be translated into an unrotated spatial description by using the equations relating the unrotated stress and strain tensors to their referential counterparts. Again, the unrotated spatial constitutive equations take a form similar to their referential and current spatial counterparts. The unrotated moduli and elastic limit functions depend on the stretch and exhibit so-called strain-induced hardening and anisotropy, but without the effects of rotation. 

I.O. Bashkin, E.G. Ponyatovsky, O.N. Senkov, and V.Yu. Malyshev, The strain-rate effect on the hydrogen-induced workability improvement of titanium alloy VT20 at temperatures 500-800°C, Phys. Met. Metall., 69 167 (1990). 

When a rubbery polymer, such as natural rubber, is stretched the molecules become aligned. This orientation leads to crystallisation. The effect of this so-called strain-induced crystallisation is to make the extended polymer stiffer than the unstrained polymer. Such crystallisation is not permanent but disappears when the sample is allowed to retract and regain its original dimensions. 

One effect of this strain-induced crystallisation is that there is a characteristic upswing in the plot of stress against strain for natural rubbers, as illustrated in Figure 7.11. 

Figure 12 shows the stress-strain curves of IER at various temperatures. A strain-induced reinforcing effect is not observed at temperatures above -10 °C. This fact may be due to network inhomogeneities caused by imperfect crosslinking. 

Strain-induced crystallization would presumably further improve the ultimate properties of a bimodal network. It would therefore obviously be of considerable importance to study the effect of chain length distribution on the ultimate properties of bimodal networks prepared from chains having melting points well above the very low value characteristic of PDMS. Studies of this type are being carried out on bimodal networks of polyethylene oxide) (55), poly(caprolactone) (55), and polyisobutylene (56). 

Comparing the strain-induced anisotropic part of the effective g-value in Equation 9.24 with the linewidth Equation 9.18 for fully correlated g-strain reveals a remarkable correspondence they are equivalent (apart from a sign ambiguity) within the substitutions... 

Just like the Zeeman interaction (S B), the hyperfine interaction (.S /) is a bilinear term and its coupling to strain (T S I), which we will call A-strain (also, -strain ), should be formally similar to the g-strain (T S B) just discussed. In the early work of Tucker on the effective S = 1/2 system Co2+ in the cubic host MgO, a shift in central hyperfine splitting was found to be proportional to the strain-induced g-shift given by Equation 9.22 (Tucker 1966). 

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