Normal stress relaxation after step strain

Calculate the stress relaxation modulus of the Rouse model (Eq. 8.55) by showing that after a small step shear strain 7 at time t 0 the correlation function of normal modes decays as Xpx t)X y(t)) — i kTjkp) exp (- tjxp). 

Fig. 56. Values of the time and strain-dependent strain energy function derivatives dW/dli and 9W/9/2 for a glassy PMMA determined from torque and normal force measurements in single-step stress relaxation torsional experiments. After McKenna (114).

Fig. 57. Values of the time and strain-dependent strain energy function derivatives Wi = 9W/9/1 and W2 = 9W/9/2 for a glassy polycarbonate determined from torque and normal force measurements in single-step stress relaxation torsional experiments, (a) >/ 0.017 0.033 A 0.050 v 0.067 0.083 O 0.10. (b) y A 0.017 0.033 o 0.050 T 0.067 v 0.083 0.10. After Pesce and McKenna (146).

Relaxation After a Step Strain for the Lodge Equation Calculate the relaxation of the shear stress and the first normal stress... 

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