A. Mestadi et al., MODELIZATION OF EXTENSIONAL EXPERIMENTS UNDER CONSTANT FORCE USING MEMORY-INTEGRAL CONSTITUTIVE-EQUATIONS AND STREAM-TUBE ANALYSIS, Rheologica Acta, 35(4), 1996, pp. 337-346
In this paper, we propose a numerical simulation of axisymmetric exten
sional experiments on a viscoelastic polydimethylsiloxane (PDMS) mater
ial, using a falling-weight extensional rheometer. The polymer behavio
ur is represented by a K-BKZ memory-integral constitutive equation, in
volving a damping function of the Wagner type. Under the assumption of
a homogeneous flow zone in the sample, a numerical model is set up, u
sing the stream-tube method and approximating functions. The governing
equations of the problem, associated to a limited number of unknowns,
are solved by means of the Levenberg-Marquardt optimization algorithm
. The numerical results are found to be consistent with the experiment
al data and reveal the importance of the non-homogeneous flow zone, in
relation to the estimation of the extensional strain rate. The calcul
ations involve the sensitivity of the model on the fluid parameters an
d those concerning the size of the initial column of fluid. The limite
d computing (CPU) time of the code is also to be underlined.