Numerical simulations of annular extrudate swell using various types of viscoelastic models

In this study, numerical simulations of annular extrudate swell of high den sity polyethylene (HDPE) were carried out. Some important viscoelastic mode ls, such as the Larson, the PTT and the K-BKZ model, were employed for the swell calculation through various types of dies. These numerical results we re compared with the experimental ones. The numerical results of the swell. behaviors were very different in each viscoelastic model, while their simp le shear flow characteristics were almost the same. As a result, the uniaxi al elongational viscosity for large deformation as the steady state region is not important, but the property for relatively small deformation has rem arkable effects on the numerical results for the die that have a uniaxial c ontraction region. Both reversible and irreversible types were tried for th e Larson model. It was found that there was a difference between the irreve rsibility assumption of the K-BKZ model and the Larson model. While there w as a serious difference in the response for reversing strain among these vi scoelastic models, the response was very important to predict annular extud ate swell behavior.