3D modeling of dual wind-up extensional rheometers

The overall picture is though more diverse, as the possibility to perform ideal uni-axial extension is very dependent of the constitutive equation. Especially the weighting between the convected relative strain tensors in the K-BKZ model seems to control the deviation from ideal behavior. Consequently, for melts or entangled liquids a proper uni-axial flow will be kept for a much wider parameter range. In fact only the appearance of a ductile necking or a large initial thickness of the sample will create a significant deviation from ideal extension. These simulations were based on MSF constitutive model.