The process- and topload-simulation routines are implemented in the simulation software Abaqus by Dassault Systèmes, Société annonyme, in Velizy-Villacoublay, Cedex, France. The coupling of these routines is achieved through software tools implemented in VB using the .NET framework by the Microsoft Cooperation, Redmond, USA.
The processes simulation was developed in . The radiation heat exchange between Polyethylenterephthalat (PET) prefom and emitter is calculated through Eq. 1 in Abaqus. The resulting energy input on the perform’s surface is used to calculate the heat generation inside the preform. Therefore, Eq. 2 is solved with a wavelength-dependent absorption characteristic. The resulting heat source ?’’’ allows determining the heat conduction through Eq. 3 with the Abaqus FEM-solver. The forming simulation requires the temperature profile of the preform. The used material model is a stretch ratio and temperature dependent Yeoh-model in Eq. 5. The described process simulation results in a formed bottle with a certain wall-thickness distribution. The elements stretch ratio is calculated through the comparison of preform and bottle elements. The “virtual prototype” of the bottle is used for further tests. A topload simulation was implemented in , that uses stretch ratio dependent material data. Furthermore an O2-barrier calculation was implemented, that uses Eq. 6, for element-wise calculation of the oxygen flow through the barrier material.
The absorption coefficient is calculated from the wavelength dependent transmission spectra in Figure 1. The forming simulation uses material-coefficients Cij of the Yeoh-model in Eq. 4 based on stress-strain-curves. These curves were measured on a lab stretcher KARO IV, by stretching PET-films at different temperatures and stretch-speeds. The resulting stress-strain-curves for different temperatures are shown in figure 1.
The material properties for the topload and the barrier simulation were measured on probes of PET bottles with different homogeneous stretch ratios. Figure 2 shows the axial secant modules for the topload simulation in axial and circumferential direction on the left as well as on the right the permeation coefficients measured in permeation chambers with a non-invasive optical sensor of the company PreSens Precision Sensing GmbH, Regensburg, Germany.