| dc.description.abstract | The stress distribution and fatigue behaviour of a thick walled closed erided pressure
vessel containing a transverse hole or cross bore with various blending geometries at its
intersection with the main cylinder bore has been investigated using a two and three dimensional
finite element approach supplemented by experimental observations.
Initially, four simple models were investigated to consider their potential for approximately
simulating the stress on the highly stressed region of the cross bore and a curved
beam model specimen was found to most closely simulate the stress distribution found in a
thick walled cylinder. This curved beam model was subsequently used in finite element
investigations and in fatigue tests to evaluate the relative differences in stress and fatigue life
when a blending radius or chamfer is introduced at the cross bore - main bore intersection of
a cylinder. The static finite element results showed that no blending geometry produced a
low local stress field although in fatigue tests curved beam models with a chamfered blending
geometry were found to have ,a marginally improved fatigue life.
The longitudinal stress existing in a pressure vessel was not taken into account in the
curved beam model. It became possible later in this work to analyse, using finite elements,
actual cross bore cylinders containing various cross bore blending geometries. The results
for cylinders having outer to inner diameters ratios of 2, 1.8 and 1.4 are presented in this thesis.
Fatigue tests were also carried out on similar specimens made from 826M40 steel using
a specially designed fatigue testing facility. The experimental results are presented and
show the plain cross bore to have marginally superior fatigue behaviour for a cylinder thickness
ratio of 2. For a thickness ratio of 1.4, fatigue life curves were found to be very similar.
From the results of this work, it has been found that a power form relationship exists
between fatigue life and the principal strain range, the shear strain range and the applied
maximum internal pressure | en |
