Interpretation of mechanical response

Prediction is very difficult, especially about the future. (Niels Bohr) 

The stress-strain curves in Fig. 4.39 to 4.41 have the characteristic shape for elastomers containing reinforcing particles. There is a rate-dependent flow stress associated with stress-activated segmental diffusion at the surface or interior of reinforcing particles, superimposed on the strain-stiffening hyperelastic stress response of the elastomeric matrix. Such a system is amenable to a quantitative description in terms 

I = 110). Nominal extension rate was 0.0042 s . Each cycle was obteiined with a different specimen [61] 

Consider a uniaxial tensile test, parallel to axis 1, say, in which at any instant the stretch is and the rate of stretching is X hence cr = cr, a-n = 0. It follows from equation (4.15) that the applied true stress cr may be expressed unambiguously as the sum of two distinct terms  

This is a useful result, as it means that stress-strain data for load-unload cycles may be used to separate out bond-stretching and conformational contributions to the stress [61]. Thus we may evaluate them as follows, applying equation (4.16) to loading and unloading, and making use of equation (4.17), for any value of elongation where the above restrictions apply (particularly where stress transients can 

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The defect question delineates solid behavior from liquid behavior. In liquid deformation, there is no fundamental need for an unusual deformation mechanism to explain the observed shock deformation. There may be superficial, macroscopic similarities between the shock deformation of solids and fluids, but the fundamental deformation questions differ in the two cases. Fluids may, in fact, be subjected to intense transient viscous shear stresses that can cause mechanically induced defects, but first-order behaviors do not require defects to provide a fundamental basis for interpretation of mechanical response data. 

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