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Title: Simulation of the mechanical and flow behaviour of bone fixation implants
Author: Zhang, Ziyu
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Titanium (Ti) porous foams produced by additive manufacturing (AM) techniques are promising for fixation devices in orthopaedic applications. These implants should possess sufficient permeability to allow vascular invasion, integration with the host tissue and also satisfy the transport requirements of remodelling bone. The mechanical properties of implants should also match those of the host tissue to ensure sufficient life span in the body. Both macro and micro-structures of implants influence the mechanical and flow properties. Techniques are therefore needed to characterise the structural parameters and to evaluate their effects on the performance of the implant. This thesis focuses on computational modelling tools based on X-ray microtomography (μCT) images to characterise the flow and mechanical properties of porous foams. The aim of the study is to develop and apply these tools on Ti implants with different structures to investigate how the design variables offered by AM technique can be used to alter the implant architecture on multiple length scales to control and tailor the flow and mechanical properties. A computational fluid dynamics model was developed to predict permeability of the implant and how AM can be used to tailor implant flow properties by controlling surface roughness at a microstructual level (microns), and by altering the strut connectivity and density at a macroscopic level (millimetre). A finite element (FE) model of compression test was developed to quantify mechanical properties of the porous implant based on three-dimensional (3D) μCT images and the work is validated and compared to the in situ experiment using μCT. Fluid flow in bone tissue has a key role in the bone remodelling process. A 3D microscale numerical model that simulates the fluid flow-induced shear stress and time dependant bone growth was developed and showed the inter-relationship between those two dynamic factors.
Supervisor: Jones, Julian ; Lee, Peter Sponsor: Stryker Corporation ; Engineering and Physical Sciences Research Council ; Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral