Developmental dysplasia of the hip (DDH) refers to some hip disorders, from mildly dysplastic to hip joint dislocation. The main feature of DDH is the deficient acetabular coverage, which is related to a small contact area in the hip joint, and causes an increase in contact pressure. Ganz periacetabular osteotomy (PAO) is a surgical procedure to correct acetabular orientation in DDH. It changes the position of the acetabulum to increase the femoral head coverage and distribute the contact pressure over the cartilage surface. The procedure of Ganz PAO is technically demanding and its success depends significantly on the surgeon’s experience. The aim of this research is to investigate whether it is possible to optimize the position of the acetabular fragment in patients suffering DDH before a Ganz PAO by using finite element (FE) analysis. Using computed tomography (CT) data from patients with DDH, five three-dimensional (3D) hip models were developed. A virtual Ganz PAO was then performed on the hip models. FE analyses were carried out on the hip models before and after virtual Ganz PAO. Contact area, contact pressure and Von Mises stress in the hip cartilage were checked and analysed in order to find an optimal acetabular position. The first virtual surgery performed was only to rotate the acetabular fragment in the lateral direction to improve the acetabular coverage. Analyses were conducted under loading conditions associated with four commonly daily activities: one leg stance, normal walking, descending stairs and knee bend. Second virtual surgery performed was to rotate the fragment in both the lateral and anterior directions and FE analysis conducted for one leg stance loading condition. Contact area, contact pressure and Von Mises stress in the cartilage all varied according to the change of the acetabular fragment position through virtual Ganz PAO. The optimal lateral position of the acetabular fragment occurs close to the inferior border of its normal range. Large anterior position of the acetabular fragment results in large contact area, low contact pressure and Von Mises stress. However, an overcorrection of the acetabular fragment, especially in the anterior correction, leads to problems in performing normal hip movements. The optimal anterior position of the acetabular fragment is therefore close to the superior limit of the normal range. In conclusion, the present analysis shows that an optimal position of the acetabular fragment for patients suffering DDH which improves the acetabular femoral head coverage in the normal range, maximizes the contact area and minimizes the contact pressure and Von Mises stress can be established using 3D models and FE analysis. This information will be useful to the surgeons for the planning of PAO.

This thesis concerns the simulation of locomotion in vertebrates. The state-of-the-art uses genetic algorithms together with solid body kinematics to generate possible solutions for stable gaits. In recent work, this methodology led to a hopping gait in a dinosaur and the researchers wondered if this was realistic. The purpose of the research carried out in this thesis was to examine whether quick and simple finite-element analyses could be added to the simulator, to evaluate a simple ―break or―not break failure criterion. A break would rule out gaits that might damage theowner‘s skeleton. Linear elastic analysis was considered as a possible approach as it would add little overhead to the simulations. The author used X-ray computed tomography and the finite element method to examine the axial loading of a barnacle goose femur. The study considered four levels of detail for a linear elastic simulation, finding that all the analyses carried out overestimated the strength of the bone, when considering safety factors. The conclusion is that to incorporate stress-strain analysis into the gait simulation requires more realistic models of bone behaviour that incorporate the nonlinear response of bone to applied loading. A new study focusing on the use of novel techniques such as model order reduction is recommended for future work. The outputs of this research include chapters written up as journal papers covering a 4D tomography experiment; a level of detail study; an analysis of a purported tendon avulsion injury in Tyrannosaurus rex and a review of the elastic properties of bone.

Lumbar intervertebral disc disorder is a spinal condition that affects the normal function of the intervertebral discs mainly due to the natural aging process. This condition can manifest itself in pain and limited motion in the legs, amongst others. Posterolateral Fusion (PLF) and Posterior Lumbar Interbody Fusion (PLIF) are two of the most used surgical procedures for treating lumbar intervertebral disc disease. Although these procedures are commonly used and performed successfully the impact in terms of the stresses developed in the posterior implants employed and in the spinal components adjacent to the surgical site has not been exhaustively investigated. In addition, the consequences of the procedure on the reduction of the Range of Motion of the lumbar spine is not clearly understood. The objective of this research is to investigate the effect of one-level spinal fusion of lumbar segment L4-L5 on the stresses and the range of motion at the remaining, adjacent lumbar levels. Four 3 dimensional finite element models of a lumbosacral spine were created from Computer Tomography data (CT scan). The models were used to investigate four surgical scenarios, including the use of 0o and 4o interbody cages, in addition to the un-instrumented spine for flexion, extension, torsion and lateral bending motions. The predictions obtained from the models enabled the mechanical behaviour of the lumbar spine following fusion surgery using 0 o and 4o cages to be investigated and compared. In addition, a clinical study was performed to quantify the reduction in the range of motion for subjects who had undergone L4/5 posterior lumbar interbody fusion surgery. The clinical results were compared to those of subjects who had not undergone surgery and to the range of motion predictions from the computational model. The results from this research demonstrate that the insertion of posterior instrumentation does not have an impact on the spinal structures above the L3/4 intervertebral disc. However, the pedicle screws and the insertion of the interbody cages causes stress levels in the area adjacent to the surgical site to rise which could promote accelerated degeneration of the discs. Additionally, this study demonstrates how the pedicle screws are affected by the surgical spinal fusion techniques. Furthermore, the investigation demonstrates how posterior lumbar interbody fusion causes the range of motion of patients that had undergone this surgery to decrease. The results from the comparison of the behaviour of the use of 0º and 4º interbody cages in L4-5 posterolateral fusion demonstrates that the stress levels in the adjacent vertebrae, intervertebral discs and pedicle screw fixation system increase when 4º are used cages than when 0º cages were employed. The results from the in-vitro study show a decrease in the range of motion of the subjects who had undergone L4/5 posterior lumbar interbody fusion surgery when compared with the subjects with no low back pain history. This indicates that the PLIF surgery combined with the normal disc degeneration is subjected to higher stresses than the healthy spine.

Doctor of Philosophy / Department of Industrial & Manufacturing Systems Engineering / Zhijian Pei / Grinding is one of the important operations employed in modern manufacturing industry to remove materials and achieve desired geometry and surface finish. Simultaneous double side grinding (SDSG) and ultrasonic vibration assisted grinding (UVAG) are two typical cost-effective grinding processes which are utilized to grind semiconductor materials and high performance ceramic materials, respectively. The objectives of this research are to investigate several technical issues in modern grinding processes by using theoretical, numerical, and experimental research approaches. Those technical issues are related to SDSG and UVAG, which have been chosen as two typical grinding processes for this research. This thesis reviews the literature on SDSG (covering process applications, modeling of grinding marks, and modeling of wafer shapes) and UVAG (covering process applications, edge chipping, and coolant effects, etc). The theoretical research work of this thesis is conducted by developing mathematical models for grinding marks and wafers shapes in SDSG of silicon wafers. These developed models are then used to study the effects of SDSG parameters on the curvature of the grinding marks, the distance between adjacent grinding marks, and the wafer shapes. The numerical research work of this thesis is done by conducting a three dimensional (3-D) finite element analysis (FEA) of UVAG process. A 3-D FEA model is developed to study the edge chipping commonly observed in UVAG of ceramics. Edge chippings not only compromises geometric accuracy but also possibly causes an increase in machining cost. A solution to reduce the edge chipping is proposed based upon the FEA simulations and validated by pilot experiments. Several experimental studies are conducted to provide new knowledge for the UVAG process. Firstly, a novel coolant delivery system is explored for UVAG machine system. Secondly, UVAG is introduced into machining of fiber-reinforced ceramic matrix composites (CMC). Results of a feasibility study and a designed experimental investigation show that UVAG is a promising process for CMC machining. Finally, an experimental study on cutting forces during UVAG of zirconia/alumina composites is conducted. The feasibility to machine different zirconia/alumina composites using UVAG is also investigated and discussed. The findings in this thesis will provide theoretical and practical guidance for modern grinding processes especially for SDSG and UVAG.

The objective of this research was to better understand how impact angle influences headform dynamic response and brain tissue deformation. A bare headform was impacted using a pneumatic linear impactor at 5.5 m/s. The impacts were directed on the front and side location at angles of 0, 5, 10 and 15° rightward rotations as well as -5, -10 and -15° (leftward) rotations at the side to examine the characteristics of the head and neckform on the results. Peak resultant linear and rotational accelerations from the headform as well as peak maximum principal strain (MPS) and von Mises stress (VMS) estimated from a brain finite element model were used to measure the effect of impact angle. Significant results were dependent upon the impact angle and location as well as the dependent variable used for comparison (p <0.05). Impact angle produced significant differences in rotational acceleration and MPS at both the front and side; however angle only had an effect on VMS and linear acceleration at the front and side locations, respectively. These findings show that the effect of impact angle is asymmetrical and is specific to the dependent variable. This study suggests that varying impact angle alone may not be as influential on headform dynamic response and brain tissue deformation and that the severity of an impact may be more of a function of how both location and angle create high risk conditions.

As the most commonly diseased heart valve, the mitral valve (MV) has been the subject of extensive research for many years. Unfortunately, the only treatment options currently available are surgical repair and replacement. Although repair is almost always preferable to replacement, it is often underperformed due to the complexity of MV repair surgeries. Consequently, there is significant interest in generating patient-specific finite element models of the MV for the purpose of simulating mitral repairs. For practical purposes transesophageal echocardiographic (TEE) images are most commonly used to reconstruct the mitral apparatus. However, limitations in ultrasound technology have prevented the detection of leaflet thicknesses. In the current study, a method was developed to accurately model variations in leaflet thicknesses using TEE datasets. Nine healthy datasets were modeled and the leaflet thicknesses were found to closely match previously reported results. As anticipated, normal valve function was also observed over the entire cardiac cycle.

Reinforcement corrosion is the most common deterioration problem observed in reinforced concrete (RC) structures located at coastal or cold regions. The corrosion process can impact the performance of these structures by inducing damage on the bonding action between concrete and steel, either by the splitting of the concrete cover due to the volumetric expansion of corrosion products or the lubricant effect at the steel/concrete interface as the corrosion by-products accumulate. The current research aims at investigating corrosion-induced deterioration of bond between steel and concrete through finite element (FE) analysis of the flexural behaviour of corroded RC components. By treating the concrete cover as a thick-wall cylinder subjected to internal pressure, the analytical evaluation of impaired bond capacity is studied first and verified against published bonding tests. Then, the formulation of a numerical model is performed using ABAQUS, wherein a link element to simulate the bond behaviour is formulated and implemented through the ABAQUS user-subroutine (UEL) feature according to the validated analytical model. By introducing corrosion-induced damages, i.e., smaller cross-sectional area of reinforcement, splitting of concrete and bond deterioration, in the FE analyses, the results of the numerical model show good agreement with experimental observations. Upon validation of the analytical and FE models, a parametric investigation is conducted, wherein the effects of concrete strength, dimension of reinforcing bars, properties of oxide products, different corrosion damage mechanisms and the corrosion location along the longitudinal reinforcement on the flexural behaviour of RC beams are studied. The results show that the analytical evaluation for bond degradation is impacted by the selection of the post-cracking material model and the thickness of cover that determine the ‘holding capacity’ after cracking initiation. Also, the density of rust by-products affects the results of the analytical model at high corrosion levels. From the FE model results, it was observed that each damage mechanism due to corrosion contribute to different levels of flexural degradation, although the flexural strength degradation is mainly due to the loss of bonding action. The parametric study also demonstrates that flexural members which have reinforcement corrosion initiated near the supports suffer greater deterioration in flexural capacity than those with damages at mid span. Finally, based on these observations, suggestions for the application of both analytical and numerical models are made.

In today’s society, dental implants are a growing solution for dental care. However, most dental components are very expensive when imported, and are purchased at premium costs solely from a few international companies. It is estimated that the current market price of dental implants is as much as one thousand times the material cost. To be cost effective in a growing competitive market, a local company is looking into producing their own components, and requires knowledge of manufacturing and quality assurance or expertise in order to validate the effectiveness of their fabricated components. These fabricated components need to be tested against currently in use market components in order to assure that prototype components are not inferior to the current market supply. The present study focuses on the analysis of the fabrication process of dental implants, specifically the abutments and screws. The objective is to compare material properties of prototype and market components to determine if the prototype components have adequate quality. Furthermore, simulated models are developed for predicting material property changes due to the manufacturing process. The material properties are determined through hardness testing and microstructure analysis. Visual inspection is then used to investigate and characterize the components. The simulations use different machining parameters, such as the feed rate and the cutting speed to determine residual stress patterns. Dental implant abutments and screws were successfully tested and compared. The prototypes show a good hardness and microstructure properties similar to market components, indicating a high level of prototype quality. The simulated models were successfully created and provided an adequate level of customization to be usable in place of future mechanical testing and showed results that complimented experimental findings. The standard cutting speed of 2000 rpm (100%) in the prototypes produced the optimal hardness and surface roughness. Prototypes were found to have an acceptable level of both hardness and surface finish for the investigated 50%, 100% and 150% of the standard 2000 rpm feed rate.

Concussions are a problem in competitive sports with growing concern over the acute and long-term consequences of repetitive head trauma. Participation in sport increases risk of concussion, particularly contact sports including rugby, hockey and football (Harmon et al., 2013). In rugby league, there are between 8.0-17.5 concussions/1000 player hours, representing roughly 10-15% of all injuries in the sport (Gardner et al., 2015). Shoulder, head, hip and knee are reported to be the most common regions that impact the head and are responsible for the greatest number of concussive injuries in rugby (Cusimano et al., 2013; Fuller et al., 2010; Gardner et al., 2014; Toth, Mcneil, & Feasby, 2005). In each of the common injury events reported in elite men’s rugby, there are unique combinations of impact conditions which include effective mass, compliance, velocity and location of impact. The head-to-head event represents a low mass, low compliance event, whereby the hip and shoulder-to-head collisions represents high mass, high compliance events. Scientists have conducted research in an effort to describe incidence and mechanisms of concussive injury in rugby, however, little is known about the biomechanics of head injury in the sport (Fréchède & Mcintosh, 2009; Fréchède & McIntosh, 2007; McIntosh et al., 2000). The purpose of this thesis is to characterize dynamic response and brain tissue deformation for (1) hip-to-head, (2) shoulder-to-head, (3) knee-to-head, and (4) head-to-head concussion events in men’s rugby. Twenty-nine (29) impact videos of diagnosed concussive injuries associated with the four common injury events were reconstructed in the Neurotrauma Impact Science Lab. Head-to-head impacts were reconstructed in this study using a pendulum system, while hip, shoulder and knee to head impacts were reconstructed using the pneumatic linear impactor. Results of this study demonstrate that the common injury events resulting in concussion in elite men’s rugby have different dynamic response characteristics. Head-to-head events produced significantly greater peak linear and peak rotational acceleration, however no significant differences in maximum principal strain between the injury events. Results of this study can be useful in reducing rates and severity of concussive injury in rugby.

Fossil tracks represent the only direct record of behaviour and locomotion of extinct animals. A computer model using finite element analysis (FEA) has been developed to simulate vertebrate track formation in cohesive substrates. This model has been designed for, and successfully run on, high performance computing (HPC) resources. A number of individual studies were carried out using the computer model to simulate both abstract indenters and virtual dinosaur autopodia. In addition to the simulation studies, two fossil tracks were described, including the first report of bird tracks at the Mammoth Site of Hot Springs, South Dakota (USA) and a re-description of a 'dinosaur tail drag' as the trace of a crocodilian. Using the computer model, it has been shown that in a wet, soft mud the indentation of a non-webbed virtual tridactyl foot created a resultant track with features analogous to 'webbing' between digits. This 'webbing' was a function of sediment deformation and subsequent failure in 3D, specific to rheology. Apparent webbing impressions were clearly developed only within a limited range of sediment conditions and pedal geometry. Indenter (pedal) geometry and morphology affect track depth independently of substrate and loading parameters. More complex morphologies interact with the cohesive substrate creating a lower effective load than that applied. In non-cohesive substrates such as sand, this effect is reversed, and it is the more compact morphologies that indent to a lesser degree. Virtual sauropod tracks were modelled, based on published soft tissue reconstructions of autopodia anatomy, and published mass/centre of mass estimates. It was shown that foot morphology and differential loading between fore- and hind- limbs leads to a range of substrates in which only the manus or pes are able to generate tracks. This offers a new mechanism for the formation of manus-only sauropod trackways, previously interpreted as having been made by swimming dinosaurs. A series of tracks were simulated using input data (loads, pedal morphologies) from four different dinosaurs (Brachiosaurus, Tyrannosaurus, Struthiomimus, and Edmontosaurus). The cohesive substrates used displayed a 'Goldilocks' effect, allowing the formation for tracks only for a very limited range of loads for any given foot. In addition, there was a strong bias toward larger animals, both in homogeneous and theoretically heterogeneous substrates. These findings imply that interpretations from track assemblages must consider that only a small proportion of the total fauna present may be recorded as a track assemblage due to substrate properties. The use of FEA to simulate dinosaur track formation has been shown to be successful, and offers a number of advantages over physical modelling including; consistency between experiments, specific control over input variables, rapid undertaking of repeatable experiments, and the ability to view subsurface deformation non-destructively. It is hoped that this work will lead to an increased interest in modelling tracks, and offer a quantitative method for studying fossil tracks.