Strain-induced hardening and

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. 

First direct evidence of flow-induced orientation of clay tactoids. Strain-induced hardening and rheopexy originate from the perpendicular alignment of clay layers to the stretching direction. 

Sinha Ray S, Okamoto K, Okamoto M (2006), Melt rheology and strain induced hardening behaviour of biodegradable poly(butylene succinate)/synthetic fluorine mica nanocomposites , Langmuir, submitted. 

We note that, with few exceptions, the plastic responses of glassy polymers have direct parallels to the corresponding processes in non-polymeric atomic glasses discussed in Chapter 7. We make full use of the detailed mechanistic models presented there and develop in detail only phenomena of strain hardening arising from strain-induced segmental molecular alignment. 

For a second comparison we chose the strain-hardening behavior of nearly glassy PET between 298 K and the glass-transition temperature of 346 K, which was studied by Zaroulis and Boyce (1997) in compression flow. Figure 8.18 shows the compression stress-strain curves of PET at a strain rate of 10 s at seven temperatures between 298 and 349 K, slightly above Tg. The DSC experiments showed that as-received material contained nearly a 9% crystalline fraction. It also needs to be noted that PET undergoes considerable strain-induced... 

Both the strain rate sensitivity and strain hardening exponent of cerium (initially in the y phase) exhibit manifestations of the various transformations as shown in fig. 8.21. There is a gradual rise in the strain hardening exponent as the temperature decreases to the y to /3 M[Pg.628]

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