Hence, any additional information about the
behaviour of fluid-filled containers under drop impact such as
pressure in a fluid when failure occurred, strain in the bottle wall,
effects of strain or pressure rate, etc. are not available. However, the
failure of fluid-filled containers under drop impact does depend on
a number of parameters such as drop impact mode, the material
properties of both the container and its liquid contents, container
geometry and design, and so on. If any parameter is changed, a new
set of tests has to be conducted. It is clear that this approach can be
very expensive, especially in design optimisation. This undoubtedly
emphasises the importance of instrumented testing, and corresponding
numerical simulation.
There has been a limited amount of work conducted in this area.
For example, Reed et al. [4,5] conducted drop experiments on both
poly-vinyl-chloride (PVC) and polyethylene (PE) bottles. They
recorded pressure histories at different positions in the bottle and
observed that the pulse time was independent of the drop height.
Reed’s work was continued by Lim [6], who conducted extensive
instrumented drop impact testing on blow-moulded 600 cm3
detergent bottles and 210-litre drums. The containers were filled
with water at different levels and dropped squarely from varying
heights onto a specially constructed plate to record the total impact
force on the floor. In order to record pressure transients, two
pressure transducers were mounted inside the containers at
various positions. He found that the magnitude of the pressure
pulse always increases linearly with the impact velocity, but
decreases parabolically with distance from the base and interpreted
his results using waterhammer theory. Later, Breedveld [7]
studied the wave speed along 20-litre drums subjected to drop
impact. He observed that there was no time delay between pressure
signals at two different positions from the base. In other words, he
claimed there was no wave travelling through the water contained
in the container. This observation has been used to establish the
mass-spring model for drop impact of fluid-filled containers.
It is clear by now that there is still no convenient method to
explain this complex problem. This paper will try to shed some
more light on the problem and give new approaches to solving it.