Szabo, Margaret Elizabeth
Local strain and microdamage assessment during micromechanical testing of single bovine trabeculae and cortical bone tissue
University of Southampton, School of Engineering Sciences,
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This work examined the mechanical properties of single bovine trabeculae and
cortical bone tissue experimentally. In particular, microdamage and local strains
were assessed for bovine bone tissue. A three-point bending experimental setup
was designed capable of measuring local strains at the surface of such small
specimens, using the digital image correlation technique. Microdamage formation
and propagation were detected using the bone whitening effect, an optical
non-invasive technique. This technique enabled to follow the progression of
local strains and microdamage in real-time from which local strains at microdamage
initiation and failure could be derived.
This technique was used to investigate three fundamental aspects of bone
mechanics. The first study examined the strain rate sensitivity of single bovine
trabeculae. No linear relationship was observed between the strain rate and the
Young’s modulus, the amount of microdamage, the maximum tensile strain at
failure and at microdamage initiation. The second study compared the mechanical
behaviour of single bovine trabeculae and similarly sized cortical bone samples.
Cortical bone tissue exhibited significantly lower maximum strains and
less accumulated damage at failure. However, no significant difference was detected
for the maximum strain at microdamage initiation. Finally, the anisotropy
of bovine cortical bone tissue was investigated. No significant difference was
found between the Young’s modulus, the amount of microdamage and failure
strains of longitudinal and tangential bone samples. However, these parameters
were significantly lower for the radial samples. For strains at whitening
onset, no significant difference was seen for the longitudinal and radial groups,
whereas the tangential values were significantly greater.
The insights gained from this work enhanced our understanding of the damage
properties of bovine bone at the microstructural level. Future work is required
to investigate the relevance of the above findings to human bone tissue.
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