Determination of material parameters of quasi-linear viscoelastic rheological model for thermoplastics and resins

In this study, an algorithm for identification of elastic and viscoelastic constants of a recently developed constitutive equation for thermoplastics and resins is presented. The equation has been applied to model the viscoelastic response of ultra high molecular weigth polyethylene. In order to determine the material parameters, a series of rheological tests has been performed. A set of equations describing one-dimensional processes has been derived and is utilized to determine the material constants. The material parameter identification leads to a set of 9 constants, i.e. 3 constants of elasticity and 6 constants of viscoelasticity. For the determined values of parameters, several validation tests have been performed.