Parameter study of stretch–blow moulding process of polyethylene terephthalate bottles using finite element simulation

摘要

In this paper, the analysis of the stretch–blow moulding (SBM) process of polyethylene terephthalate (PET) bottles is studied by the finite element method (FEM). In this simulation, owing to the symmetry of bottle geometry, the parts are considered as an axisymmetric model. A hyperelastic constitutive behaviour was calibrated using material data available in literature in variant high temperatures and strain rates and was used in the numerical simulation. Hydrostatic pressure with convention heat transfer has been used instead of a blowing process. Comparisons of numerical results with experimental observations demonstrate that the model can predict an overall trend of thickness distribution, especially in regions between 30 mm to 90 mm from the bottle bottom. However, some differences can be seen in regions 10 mm and 125 mm. These results can be used for an overall prediction of bottle properties such as final bottle thickness and a defect-free production because they are governed by orientation and crystallinity, which are highly temperature and strain dependent. Also, with definition of the critical area in bottle forming, the parametric studies are conducted on the effect of friction condition, heat transfer coefficient, and initial pre-blowing air entrance time delay on bottle thickness. Through the study, it becomes clear that the proposed model is applicable for simulating the stretch-blow moulding process of PET bottles, and is capable of offering helpful knowledge in the production of bottles and the design of an optimum preform.