Unrelaxed compliance/modulus

Figure 8.12 Creep compliance (inverse of modulus) as a function of log (time). The rate of transition from the unrelaxed compliance (higher modulus) to the relaxed compliance (lower limiting modulus) depends on the parameter m.

Fig. 5.4 In a model with a single relaxation time, r, = 10 s, relaxed ereep eompliance /r = 1.0 GPa and unrelaxed shear modulus = 1.0 GPa, the changes in the creep compliance, from unrelaxed, /u, to relaxed, Jr, and corresponding changes in storage modulus (t) from relaxed, r, to unrelaxed, /lu, with increasing angular frequency co are shown, as are also associated changes in the loss compliance J"(t) and loss modulus, (after McCrum et al. (1967), with modification).

Equations (7.26) are called dispersion relations and analogous equations can be derived for /, and J2 (see problem 7.7) and for more general models. They can also be derived for the real and imaginary parts of the dieleetrie constant (see section 9.2.4). The limiting values of G, and /, at low frequencies are called the relaxed modulus and compliance, G, and J, and the limiting values at high frequencies are called the unrelaxed modulus and compliance, G and / ... 

In trying to identify relaxations it is often useful to consider their relative strengths. The standard definition of the relaxation strength for mechanical relaxations is that it is the difference between the unrelaxed and relaxed modulus or compliance, or — J. Determination of... 

A material, which can be described as an SLS, was found to have unrelaxed and relaxed Young s modulus values of 70 and 50 GPa, respectively. Determine the relaxation and retardation times. Plot graphically the compliance of the material as a function of time, under the action of a constant uniaxial tensile stress. 

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