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Optimal Design for PET Bottle to Maximize Reliability

Finite Element Analysis and Experimental Work

  • Hassan S. Hedia , Saad Aldousari and Fouad Bin Zager
From the journal Materials Testing

Kurzfassung

This study presents the new development in the 1.8l Eagle shape of an edible oil bottle made of polyethylene terephthalat (PET) virgin resin. The study refers to an increasing of the stretch ratio between the bottle and the preform. The new preform design offers several advantages including light-weight, reduced electrical consumption, maintaining good quality level and improvement of some mechanical properties (ductility and toughness) for many bottle applications. Mainly, the study has been divided into two parts, i.e. experimental work and finite element analysis. Regarding the experimental work, substantial modifications of the injection unit have been made to produce the new preform fitting to the new stretch ratio. The modification comprises the pair of injection cores, cavity, guide ring, and two pairs of split insert. Also, in the experimental work 126 tension tests with standard samples from bottles before and after the modification have been performed. The specimens have been taken from seven areas of the bottle and have been loaded in two directions (axial and hoop). Finally, the new bottle quality level has been experimentally checked by load tests, stacking tests and center closure leak tests. For the finite element simulations, solid modeling of the complex bottle shape by SolidWorks has been carried out, followed by finite element analyses with Abaqus to calculate the stress and displacement in the bottle areas and also to compare the behavior of the stress distributions for old and new bottles. Among others, as the major result of this study a 16.2% reduction in the bottle weight has been achieved which will reduce the material cost. Regarding the mechanical properties for the new bottle, like ductility and toughness, a number of significant improvements have been made in many bottle areas. In the most critical area, the ductility has been improved by 180% and the toughness by 35%. The non-linear finite element analyses have revealed a maximum stress reduction of 36% as compared to the old bottle.

Kurzfassung

Optimales Design zur Erhöhung der Zuverlässigkeit einer PET- Flasche — Finite Elemente-Berechnungen und experimentelle Untersuchungen. Im vorliegenden Beitrag wird eine Studie präsentiert, in der die 1,8 l Eagle-Form einer Speiseölflasche aus fabrikneuem Polyethylen-Terephthalat (PET) Kunstharz neu entwickelt wurde. Die Studie bezieht sich auf die Erhöhung des Streckverhältnisses zwischen der Flasche und der Vorform. Das neue Design der Vorform bietet verschiedene Vorteile, einschließlich eines niedrigen Gewichtes, eines reduzierten Energieverbrauchs, dem Erhalt eines guten Qualitätsniveaus und der Verbesserung einiger mechanischer Eigenschaften (Duktilität und Zähigkeit) für viele Anwendungsfälle der Flaschen. Insgesamt ist die Studie in zwei Teilen durchgeführt worden, einer experimentellen Arbeit und Finite Elemente-Berechnungen. Bezüglich der experimentellen Arbeit sind substanzielle Änderungen der Einspritzeinheit durchgeführt worden, damit sich die Vorform während der Produktion dem neuen Streckverhältnis anpasst. Die Modifikationen umfassen das Paar der Einspritzkerne, den Hohlraum, den Führungsring und zwei Paare von Spaltbuchsen. Weiterhin sind im Rahmen der experimentellen Untersuchungen 126 Zugversuche mit Standardproben aus den Flaschen vor und nach ihrer Modifikation durchgeführt worden. Hierzu sind Proben aus sieben Bereichen der Flaschen entnommen worden und in zwei Richtungen (achsial und tangential) gezogen worden. Schließlich ist das Qualitätsniveau der Flaschen experimentell geprüft worden mittels Belastungstests, Stapelversuchen und Lecktests am Zentralverschluss. Für die Finite Elemente-Simulationen ist Solid Modeling der komplexen Flaschenform mittels SolidWorks ausgeführt worden, gefolgt von Finite Elemente-Analysen mit Abaqus, um die Spannungen und die Verschiebungen in den Flaschenbereichen zu berechnen und auch um das Verhalten der neuen gegenüber der alten Flasche anhand der Dicke zu vergleichen. Unter anderem konnte als wesentliches Ergebnis dieser Studie eine Reduzierung des Flaschengewichtes um 16,2% erzielt werden, was die Materialkosten senken wird. Bezüglich der mechanischen Eigenschaften, wie Duktilität und Zähigkeit, sind eine Reihe von signifikanten Verbesserungen in vielen Flaschenbereichen erzielt worden. In dem kritischsten Bereich ist die Duktilität um 180% und die Zähigkeit um 35% verbessert worden. Die nichtlinearen Finite Elemente-Analysen haben eine maximale Abnahme der Spannungen um 36% im Vergleich zur alten Flasche ergeben.


Prof. Dr. Hassan S. Hedia, born 1959, is professor of materials and solid mechanics. He is working at the King Abdulaziz University, KSA. He achieved his BSc in 1981 from the Mechanical Engineering Department at the Cairo University, Egypt, and his MSc in 1989 at the Mansoura University, Egypt. His PhD achieved Prof. Hedia from the Mechanical Engineering Department at the Leeds University, UK, and the Mansoura University, Egypt under channel system. His fields of interest are advanced materials, fracture mechanics, stress analysis, and biomechanics.

Dr. S. M. Aldousari, born 1956, is an assistant professor at King Abdulaziz University, KSA. He achieved his BSc in 1980 from the Mechanical Engineering Department at the Collage of Engineering, King Abdulaziz University, KSA, and his PhD and MSc in 1993 from the Bradford University, United Kingdom. His field of interest is manufacturing technology.

Eng. Fouad Omar Bin Zager, born 1980, got his BSc grade and graduated from the King Abdulaziz University (KAU) Jeddah Saudi Arabia in 2003 as Mechanical Engineer/Production & Mechanical Systems Design. Also he completed his education and achieved the MSc and graduated from the King Abdulaziz University (KAU) Jeddah Saudi Arabia in 2009 in the Mechanical Engineering/Production & Mechanical Systems Design. Fouad started his career in 2003 in Afia International Co. Jeddah - Saudi Arabia and he passed through series of positions starting with Management Trainee, Engineering Support Manager, PET/Poly-Ethylene Terephthalate (Bottle Making) Manager then Packaging Department Manager.


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Published Online: 2013-05-31
Published in Print: 2010-06-01

© 2010, Carl Hanser Verlag, München

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