Stress Relaxation after Cessation of Steady Elongational Flow

We next consider stress relaxation after cessation of steady elongation flow. In this case there is flow at a steady elongational rate ic0 from time — oo to time 0. At time t = 0 the elongational flow ceases, and the fluid is held stationary. For t 0, k = 0 and the stresses relax as a function of time. The equation to be solved for the distribution function tp is 

Substitution of this series into the above differential equation and using the above initial condition gives  

The functions of t on the right side of Eq. (17.9) are similar in shape to those given for the shear stress relaxation in Fig. 6. We know of no experimental curves for this type of experiment. 

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Stress Relaxation after Cessation of Steady Elongational Flow... 

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