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|Title: ||Experimental and numerical analysis of deformation and fracture of cortical bone tissue|
|Authors: ||Abdel-Wahab, Adel A.|
|Keywords: ||Cortical bone tissue|
|Issue Date: ||2011|
|Publisher: ||© A. A. M. Abdel-Wahab|
|Abstract: ||Bones are the principal structural components of a skeleton; they provide the body
with unique roles, such as its shape maintenance, protection of internal organs and
transmission of muscle forces among body segments. Their structural integrity is
vital for the quality of life. Unfortunately, bones can only sustain loads until a certain
limit, beyond which it fails. Usually, the reasons for bone fracture are traumatic falls,
sports injuries, and engagement in transport or industrial accidents. The stresses
imposed on a bone in such activities can be far higher than those produced during
normal daily activities and lead to fracture. Understanding deformation and fracture
behaviours of bone is necessary for prevention and diagnosis of traumas. Even
though, in principle, studying bone’s deformation and fracture behaviour is of
immense benefit, it is not possible to engage volunteers in in-vivo investigations.
Therefore, by developing adequate numerical models to predict and describe its
deformation and fracture behaviours, a detailed study of reasons for, and ways to
prevent or treat bone fracture could be implemented. Those models cannot be
formulated without a set of experimental material data. To date, a full set of bone’s
material data is not implemented in the material data-base of commercial finiteelement
(FE) software. Additionally, no complete set of data for the same bone can
be found in the literature. Hence, a set of cortical bone’s material data was
experimentally measured, and then introduced into the finite-element software.
A programme of experiments was conducted to characterise mechanical properties
of the cortical bone tissue and to gain a basic understanding of the spatial variability
of those properties and their link to the underlying microstructure. So, several types
of experiments were performed in order to quantify mechanical properties of the
studied bone tissue at macro- and microscales under quasi-static and dynamic
loading regimes for different cortex positions called anterior, posterior, medial and
lateral. Those experiments included: (1) uniaxial tension and creep tests to obtain
its elastic, plastic and viscoelastic properties; (2) nanoindentation tests to
characterise its microstructural elastic-plastic properties; (3) Izod tests to investigate
its fracture properties under impact bending loading; (4) tensile-impact tests to
characterise its impact strength and fracture force when exposed to a longitudinal loading regime. All the experiments were performed for different cortex positions
and different directions (along the bone axis and perpendicular to it) when possible.
Based on the results of those experiments, a number of finite-element models were
developed in order to analyse its deformation and fracture using the extended finiteelement
method (X-FEM) at different length scales and under various loading
conditions. Those models included: (1) two-dimensional (2D) FE models to simulate
its fracture and deformation at microscale level under quasi-static tensile loading.
Additionally, the effect of the underlying microstructure on crack propagation paths
was investigated; (2) 2D and three-dimensional (3D) FE models to simulate its
fracture and deformation at macroscale level for the Izod impact test setup. In
addition, the applicability of different constitutive material models was examined; (3)
3D FE models to simulate its fracture and deformation at macroscale level for
tensile-impact loading conditions. The developed models provided high-quality
results, and most importantly, they adequately reflected the experimental data.
The main outcome of this thesis is a comprehensive experimental analysis and
numerical simulations of the deformation and fracture of the cortical bone tissue at
different length scales in response to quasi-static and dynamic loading.
Recommendations on further research developments are also suggested.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
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