R. van Dijk

Lateral deformation of plastic bottles: experiments, simulations and prevention

Mass reduction of plastic bottles containing non-carbonated liquids calls for advanced design approaches. Weight reduction of bottles consequently influences the mechanical performance of the bottle. This performance involves top load, vacuum and impact resistance. The present paper studies the lateral deformation of a bottle due to an internal vacuum. Similar studies have been carried out before, but until now the allowable deformation has never been related to the initial headspace of the bottle. If a bottle design is able to compensate for a potential vacuum in an aesthetic manner, then panelling will not occur. Changing the vacuum resistance of a bottle will result in a different top load. Current computational techniques enhance our understanding of the problem and provide tools to achieve solutions to it.

Simulation of closed thin-walled structures partially filled with fluid

For closed structures, the enclosed gas volume can contribute significantly to the strength and stiffness of a structure. The present paper describes the use of a gas element which is incorporated into finite elements for shells. In addition, a method to solve the governing set of equations efficiently is described. The method has been applied to a typical packaging example, namely a closed filled bottle. To validate the proposed method, numerical studies have been compared with experiments.

Topology optimization for submerged buoyant structures

ABSTRACT This paper presents an evolutionary structural topology optimization method for the design of completely submerged buoyant modules with design-dependent fluid pressure loading. This type of structure is used to support offshore rig installation and pipeline transportation at all water depths. The proposed optimization method seeks to identify the buoy design that has the highest stiffness, allowing it to withstand deepwater pressure, uses the least material and has a minimum prescribed buoyancy. Laplaces equation is used to simulate underwater fluid pressure, and a polymer buoyancy module is considered to be linearly elastic. Both domains are solved with the finite element method. Using an extended bi-directional evolutionary structural optimization (BESO) method, the design-dependent pressure loads are modelled in a straightforward manner without any need for pressure surface parametrization. A new buoyancy inequality constraint sets a minimum required buoyancy effect, measured by the joint volume of the structure and its interior voids. Solid elements with low strain energy are iteratively removed from the initial design domain until a certain prescribed volume fraction. A test case is described to validate the optimization problem, and a buoy design problem is used to explore the features of the proposed method.

Accurate design sensitivities for closed-filled structures – application to plastic bottles

Abstract.Many efficient structural optimization algorithms require gradient information. Semi-Analytical (SA) design sensitivities are rather popular, as they combine ease of implementation with computational efficiency. For closed-filled structures also the effects of internal pressure changes and solubility of the gas in the fluid may be important. Typical examples for which these aspects are relevant can be found in packaging, e.g. edible-oil bottles. The present paper focuses on design sensitivities for such closed-filled structures. The design sensitivities are based on a refined SA formulation for the structure, whereas the contribution related to its contents is evaluated analytically.

The influence of solubility effects on the pressure increase during deformation of closed thin-walled structures

Abstract In structures with an internal volume, the enclosed gas can significantly contribute to the strength and stiffness. If this enclosed volume also contains a fluid then an exchange of components between the gas and fluid can take place. The present paper describes these solubility effects and presents a method to account for the solubility effect in structural analyses. The method described has been studied on a typical packaging problem, namely a closed filled bottle under vertical compression. The numerical studies were validated by experiments.

Influence of the material properties of a tub on its top load strength

Every time a new package is being developed similar problems have to be faced. These problems involve material and supplier choice, pack requirements, manufacturing performance of the pack, etc. This paper describes a study of the influence of material properties on the top load strength of a tub for frozen products. Additionally, several numerical simulations have been carried out in order to find general guidelines for new packaging developments. Copyright

Search for gamma-ray line emission from supernova SN 1991T with COMPTEL

The imaging Compton telescope COMPTEL on the Compton observatory CGRO measures γ‐rays in the energy range 0.7–30 MeV with an energy resolution of 9.7% FWHM at 1 MeV. From June 15 to 28 and again from October 3 to 17, 1991 the region containing the supernova SN 1991T was observed. A search for γ‐ray line emission from the supernova was performed. No line emission was detected. Upper limits for the two predicted lines at 847 keV and at 1.238 MeV could be derived. These limits were compared with the predictions of several theoretical models. Two of the models predict flux levels just above our upper limits.