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Stability studies on cellular-walled circular cylindrical shells

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Zou, Rong Dar (1993) Stability studies on cellular-walled circular cylindrical shells. PhD thesis, University of Tasmania.

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Abstract

The present study deals with the stability behaviour of
cellular-walled cylindrical shells subjected to simultaneous loading
of axial compression and external pressure. In particular, the
effect of high fluid pressure within the cells on the buckling
behaviour of the shell is considered.
The form of cellular-walled shell originated from a
consideration of fossil shell remains belonging to the Nautiloid
Cephalopod group. These extinct animals (relatives to the modern
day pearly nautilus) grew to about 300mm in length and had an
exoskeleton in the form of a conical shell with a small apex angle.
However, the unique feature of the shell of this fish was that it
contained small closely spaced holes running longitudinally in the
shell wall. Interest 'in these fossil shells originated from
discussions with Dr. M.R. Banks, a paleontologist at the University
of Tasmania. Dr. Banks was interested to discover why the
shellfish should want to build its shell in such a particular form.
Other than for the obvious conclusion that a cellular wall has
better bending stiffness than a solid wall of the same mass, there
appeared to be no particular reason for the specific form of this
shell. From a strength point of view, there appears to be no
advantage in the shell having longitudinal holes over
circumferential or spiral holes, and spiral holes would be easier for
the shell fish to manufacture. This study showed both theoretically
and experimentally that a possible answer lies in the stability
behaviour of this particular form of shell.
The cellular-walled cylindrical shell can be
characterized as a pseudo-orthotropic cylindrical shell with the
principal directions axially and circumferentially oriented.
Different effective Young's moduli had to be used for tension and
bending. A theoretical analysis, based on Flugge's linear buckling
theory, resulted in simple interaction formulas for buckling under
external pressure, axial compression and cell pressure.
Cellular-walled model shells have been made out of
epoxy by an adaptation of the spin casting process developed by
Tennyson. These shells have 360 longitudinal holes each of 0.7mm
diameter, shell internal diameter 153mm, wall thickness 1.2mm and
length 245mm. The tests of the model shells were carried out on a
rigid test machine with parallel platens. Since the shells are cast
with a free surface on the inside they are internally reflective. An
optical system making use of the reflective surface was used to
monitor buckling and prebuckling deformations. Test data was
logged into a PC. Southwell plots were then employed to predict
axial buckling loads. Because of the likelihood of the shell
shattering on buckling, actual collapse loads were the final values
obtained. Test data confirmed the theoretical predictions.
Both theoretical and experimental results showed that
shells of this type with pressurized cells exhibit significantly
improved stability, hence they appear to have potential in
engineering applications, particularly in marine situations.

Item Type: Thesis (PhD)
Keywords: Shells (Engineering), Buckling (Mechanics)
Copyright Holders: The Author
Copyright Information:

Copyright 1993 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references (p. 178-190). Thesis (Ph.D.)--University of Tasmania, 1994

Date Deposited: 04 Feb 2015 23:23
Last Modified: 24 Aug 2016 04:34
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