/library/oar/handle/123456789/84929 2025-11-08T18:37:01Z /library/oar/handle/123456789/93873 Title: Quantitative analysis of stability after fracture fixation in relation to the altering of different fixation parameters Abstract: Throughout history, the treatment of bone fractures has always included some form of reduction of the fracture gap between the bone fragments, followed by splinting in order to support the injury. In Neolithic times, humans have attempted to correct the deformities from fractured bones, with evidence of good unions between the bone fragments. Society has always improved the technology and innovation in order to obtain the perfect union for fractured bones which are at an increasing rate, as mal-union could produce economic and social disability. The use of internal fixation in the treatment of bone fractures is a common method to aid the healing process which is highly dependent on the stability of the mechanical environment around the fracture area. Fixation techniques aim to provide sufficiently rigid stabilization of the fracture to allow loads to be applied to the injured limb whilst allowing the biological process of fracture healing. The primary objective for this study is to analyse the stresses and strains present under load in a fractured femur fixed with a standard fracture-fixation plate and screws. Furthermore, the study looks at and quantifies how varying the parameters such as plate thickness and different screw configuration affects the mechanical stability at the fracture site. In order to achieve the analysis, an FE model was created on Ansys. A cylindrical model was created in order to simulate the femoral diaphysis and the appropriate material properties were assigned to the model. A typical 6mm fracture fixation plate, and a typical 60mm bi-cortical screw were also modelled and placed on the lateral side of the bone. Four different screws configurations were assigned to the plate, following the format of 2 screws near the fracture, 2 screws set far from the fracture, 2 screws per segment, and 3 screws per segment. Furthermore, different plate thicknesses were also created for the same screw configurations, with the 6mm plate acting as the standard, followed by a 3mm, 9mm, and a 12mm plate. Each construct was set as a load-sharing construct and loaded up to 342N. The model was verified by simulating the results on a bovine femur sample. From the analysis performed it was observed that the first principal strains in the 6mm plate were found to be in the range between 5% and 7%, which allows secondary healing through callus formation. The third principal strains were found to be in the range of 14% to 22% on the un-plated medial side of the bone. This strain would then be reduced as the callus forms from the plated side and travels to the medial side until the ideal mechanical conditions are reached. Furthermore, the strain magnitude with 6 screws was found to be the smallest for each respective plate while the 2 screws closest to the fracture showed the largest strains. The plate thickness with the least overall strain was found to be the 6mm, followed by the 9mm which showed similar values. The 12mm plate showed the largest strain] values for each construct. Description: M.Sc.(Melit.) 2021-01-01T00:00:00Z /library/oar/handle/123456789/93872 Title: Comparison of the performance of the microprocessor knee to a healthy knee during gait Abstract: Individuals that have undergone a trans-femoral amputation require a prosthetic incorporating an artificial knee joint in order to enable them to walk unassisted. Microprocessor-controlled Prosthetic Knees enable this joint to be controlled by a computer in order to behave more like a natural human knee. The aim of this study was to attempt to identify any limitations in currently available Microprocessor-controlled Prosthetic Knees that may exist when compared to healthy human knees. Two amputees fitted with Microprocessor-controlled Prosthetic Knees were recruited as well as a control subject to represent healthy human knees. Gait studies were conducted at three self-selected speeds along a level walkway. As one of the subjects also owned a non-Microprocessor-controlled Prosthetic Knee, it was included in the study as an additional data point. The resulting data showed some small differences, but the limited data available meant that a few inconsistent results in some data sets made up a significant percentage of the available data. Due to the limitations encountered during this study, chiefly the significantly limited availability of participants fitted with Microprocessor-controlled Prosthetic Knees, the results of this study are limited. As one amputee had a bilateral trans-femoral amputation and the other had a unilateral trans-femoral amputation, it was not even possible to identify if any inconsistencies were due to the individual or the prosthetics. As such, it is not possible to reach any definitive conclusions with the data available, other than that, under the test conditions encountered during the gait studies, Microprocessor controlled Prosthetic Knees are able to enable an amputee to walk with a good approximation of natural human gait on the prosthetic limb. A wider ranging study would be necessary to determine the limitations of that approximation with any certainty. Description: M.Sc.(Melit.) 2021-01-01T00:00:00Z /library/oar/handle/123456789/93856 Title: 3D printing of cardiac structures in congenital heart disease Abstract: Congenital heart disease (CHD) is the most common congenital disorder diagnosed in newborns. It afflicts approximately 0.8% to 1.2% of live births worldwide but the mortality rate and incidence vary around the world. CHD is categorized as one or more abnormalities of the heart or great vessels from birth. Although the potential aetiologies of CHD have been extensively investigated, only about 15% of cases have been attributable to a known cause. For families and patients, understanding CHDs could be critical for them to be able to comprehend the benefits of treatment and potential risks. The spatial complexity of the heart renders the creation of 3D models an important teaching aid. The educational promises of cardiac 3D models are endless due to the accurate anatomical structure, material colour, reproducibility, flexibility, as well as scalability. As newer technology becomes more readily available, this creates more opportunity to recreate the anatomy from CT, MRI, and echocardiography data to produce 3D models with precise detail. This study aims to investigate whether 3D printed models will increase the level of confidence and to help improve the understanding of the details in CHD patients to medical professionals. This thesis will investigate the production of these patient specific 3D models using CT and MRI scans to ensure better understanding with patients. The author predicts that these models will notably increase the understanding of the patients and their families and will facilitate their understanding at a more rapid pace rather than observing a 2D representation. Description: M.Sc.(Melit.) 2021-01-01T00:00:00Z /library/oar/handle/123456789/84938 Title: Numerical modelling of advanced materials subjected to high-energy particle beam impacts Abstract: The High-Luminosity Large Hadron Collider (HL-LHC) upgrade for the LHC brings with it an increase in beam energy, necessitating improvements in all systems. The development of novel, high-performing materials is crucial in assuring targets are achieved. This is especially true in the context of collimators and other beam intercepting devices, which are required to cope with elevated intensities, while delivering a lower contribution to machine impedance. For this reason, experimental campaigns such as those conducted in the HiRadMat facility at the European Organisation for Nuclear Research (CERN) are essential for testing of materials under intense particle beam impact. Thermal and structural measurements allow for the validation of mathematical models describing the material behaviour, which are implemented in numerical models simulating the experimental scenario. Once validated, such models can be applied to simulate more complex, full-scale scenarios. In this Ph.D. study, a number of materials of interest in the field of particle accelerators and other thermomechanical applications are studied. Research on available literature highlights the need for accurate mathematical models describing the behaviour of materials under the extreme conditions imposed by quasi-instantaneous particle beam impacts. With this in mind, models for Silicon Carbide (SiC), Titanium Zirconium Molybdenum (TZM) alloy, and Copper Diamond (CuCD) metal-matrix composite are proposed and applied in finite element analyses modelling beam impacts from the HRMT36 experiment. The large amount of data collected in the experiment is used to benchmark computed numerical results. The material models put forward can be applied in analyses modelling impacts on collimator jaws and other absorbers and targets commissioned in CERN’s accelerator complex. The models are found to be able to successfully simulate various impact scenarios from the HRMT36 experiment, as well as phenomena of interest such as boundary condition effects and wave propagation in failure scenarios. Further study is conducted on the behaviour of CuCD on a mesoscopic level, for which a numerical model is built to simulate wave-particle interaction for particle-reinforced composites subjected to intense impacts. Additionally, a tabular equation of state for the material is formulated from constituent material data. The work presented also identifies a number of key areas of interest for future study of the materials considered, namely related to material testing at elevated temperatures and high strain-rates, which would allow for the full description of the material behaviour for the application in question. Description: Ph.D.(Melit.) 2021-01-01T00:00:00Z