Abstract:
The present study is concerned with the assessnent of structural steel
fracture toughness, as close to real service loading conditions as practically
possible in the laboratory, using small scale specimens. The effects of
stored strain energy content is evaluated for slow-static and dynamic COD
tests for maximum load and cleavage instability.
The literature reviews elastic-plastic fracture mechanics and goes
on to study the effect of stored strain energy, the COD technique and dynamic
testing procedures presently available.
Static and dynamic fracture toughness testing using the COD technique
is carried out on BS4360 -
50D structural steel in its normalised state.
The testing procedures used closely relate to either the BS5762 COD standard
or BS5447 plane strain standard. The specimen size tested is 2B =U= 24 mn,
with a fatigue notch size of approximately a/W between 0.48 and 0.57.
Photographic-macros and SEM fractography were carried out after the
specimens were tested to assess the micromechanism processes operative
during a fracture test.
It is believed the present work is of special significance to determinate
structural design using structural steel, for example with liquefied gas
pressure vessels. The resulting test data available from this thesis is
envisaged to be the closest approach to real service "true limit severity",
and consequently is beneficial to fracture prevention technology.