With the desire for conventional coal-fired power plants to perform flexible operations, the impact of this operation has become important to the field of steam turbine modelling. This study sought to develop a computationally inexpensive turbine model with minimal OEM intervention in order to predict the internal clearances of high-pressure and intermediate-pressure turbines from Eskom's current turbine fleet. The study saw the utilisation of the Nozzle Analogy theory to develop a 1D multistage turbine thermofluid model as well as the development of a representative 1D turbine process model in order to predict the internal temperature gradients promoted within a steam turbine during transient operation. From this model a further 3D FEA turbine model of both the HP and IP turbine units were developed from simple turbine diagrams to apply the predicted temperature boundaries and predict the thermal and structural response of turbine components during transient loading during a full Cold Start procedure. The result of this study was the successful validation of the 1D and 3D Turbine models against plant data from the candidate unit. This was in the form of known process data of unit performance, as well as thermocouple and differential expansion data taken from sensors housed on the turbine unit itself. Through the validation of these parameters, various calibrations techniques were developed over the course of the study with these techniques allowing investigators to gain insight into turbine aging, operator intervention as well as brought turbine component response. The successful establishment of the paired turbine model allowed investigators to evaluate the cold clearances defined during construction and maintenance of these turbine units in industry, which contributes greatly to the availability and efficiency of the unit during these transient operations. Additionally, the establishment of this model allowed for the investigation of the role that start up speed has on turbine component response. This study demonstrated that the development of such a modelling methodology was possible and yielded results with were accurate and insightful in understanding turbine component responses which are otherwise impossible to measure during real-world operation.

In collaboration with Kongsberg Automotive, the thesis focuses on material selection and redesigning the shift fork for additive manufacturing using topology optimization. The shift fork is a component in the gear shifting mechanism in the automotive industry. The current shift fork at Kongsberg is manufactured from aluminum using die-casting. This design and material do not withstand huge dynamic loads in commercial vehicles. The material to withstand the loading conditions and is widely available across powder manufacturers is selected using the weighted properties method. The topology optimization of the design resulted in a 50 % reduction in mass. The shift fork's two legs undergo uneven load distribution due to eccentricity. The optimized models are simulated using Finite Element Analysis to validate the design. The optimized design is obtained such that the difference in displacement between both legs is within 50 %. Numerous metal powder manufacturers and 3D printing service providers were contacted to understand the current additive manufacturing market.

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Compared to traditional thermal spray, cold spray as a new emerging surface treatment eliminates or substantially reduces phase transformation of deposited material and reduces coating porosity. Therefore, the appearance of this new type of surface treatment and additive manufacturing process has attracted considerable attention from researchers. In this research, three-dimensional modeling of Al6061-T6 particle impact and cohesion process was simulated by utilizing commercial finite element analysis (FEA) software ABAQUS/Explicit. To guarantee that a stable bonding phenomenon can be realized in the scope of physical validity, a built-in cohesive contact behavior model was implemented in the simulation to understand the bonding phenomenon. A non-planar surface was introduced to replace the usual planar impacted surface to mimic micron-scale curvature of the sprayed target in the real condition. Simulation models of spraying particles impact on positions with spray angle corresponding to 90°, 80°, 70° were created to investigate the effect generated by the curvature for the residual stress after bonding. Curvature function was exploited to describe the non-planar surface wavy condition derived from optimized impacting angle for achieving bonding phenomenon. This numerical simulation work can provide further insights for the residual stress evolution status in the condition of realized cohesion between impactor and non-planar surface after a kinetic peening process. Beneficial suggestions toward cold spray technology utilization in additive manufacturing areas are concluded from the results of the numerical simulation.

Femoroacetabular impingement (FAI) is recognized as a pathomechanical process that leads to hip osteoarthritis (OA). It is hypothesized that mechanical stimuli are prominent at higher range of motions in hips with cam FAI (aspherical femoral head-neck deformity). Adverse loading conditions can impose elevated mechanical stimuli levels at the articulating surfaces and underlying subchondral bone, which plays a predominant mechanical role in early OA. The aim of this research was to determine the levels of mechanical stimuli within the hip, examining the effects of severe cam impingement on the onset of OA, using patient-specific biomechanics data, CT data, and finite element analysis (FEA). Patient-specific hip joint reaction forces were applied to two symptomatic patient models and two control-matched models, segmented from patient-specific CT data. The finite element models were simulated to compare the locations and magnitudes of mechanical stimuli during two quasi-static positions from standing to squatting. Maximum-shear stress (MSS) was analyzed to determine the adverse loading conditions within the joint and strain energy density (SED) was determined to examine its effect on the initiation of bone remodelling. The results revealed that peak mechanical stimuli concentrations were found on the antero-superior acetabulum during the squatting position, underlying to the cartilage. The MSS magnitudes were significantly higher and concentrated for the FAI patients (15.145 ± 1.715 MPa) in comparison with the MSS magnitudes for the control subjects (4.445 ± 0.085 MPa). The FAI group demonstrated a slight increase in peak SED values on the acetabulum from standing (1.005 ± 0.076 kPa) to squatting (1.018 ± 0.082 kPa). Insignificant changes in SED values were noticed for the control subjects. Squatting orients the femoral head into the antero-superior acetabulum, increasing the contact area with the cartilage and labral regions, thus resulting in higher peaks behind the cartilage on the acetabulum. The resultant location of the peak MSS and SED concentrations correspond well with the region of initial cartilage degradation and early OA observed during open surgical dislocation. Due to the relatively low elastic modulus of the articular cartilage, loads are transferred and amplified to the subchondral bone. This further suggests that elevated stimuli levels can provoke stiffening of the underlying subchondral plate, through bone remodelling, and consequently accelerating the onset of cartilage degradation. Since mechanical stimuli results are unique to their patient-specific loading parameters and conditions, it would be difficult to determine a patient-specific threshold to provoke bone remodeling at this stage.

In this thesis an investigation of the shear stiffness and capacity of joints between pre- fabricated concrete elements regarding to different material properties is reported. Two different models of shear key joints, connected to prefabricated walls, were cre- ated in the non-linear finite element software, ATENA 3D, with the aim to estimate a realistic behaviour of the joints regarding to the external loads.

Car collisions are, unfortunately, not uncommon and cause 1.35 million deaths each year worldwide. Children are often occupants in cars and to ensure their safety, child restraint systems (CRSs) have been developed. However, CRSs need to be used correctly to be efficient. Several studies, such as field investigations and Q-dummy tests, have shown that a misuse of a CRS can increase the risk of injuries. Typical misuses for a forward-facing CRS and a booster seat, with two real accident parameters, were constructed and simulated using the PIPER child human body model. The kinematics of each case were compared with injury parameters of the head, neck and abdomen. Comparing the parameters to existing injury criteria showed that most of the cases end in AIS3+ head injury, even cases with no misuse. When comparing the results of misuses to the cases where the CRS was correctly used, the dominant result was that misuse resulted in being less effective to protect the child. Moreover, results of chosen misuses compared to Q-dummy tests correlated with their results. Results from this thesis illustrate how important it is for parents to restrain children and route the belt correctly.

In applications spanning across aerospace, marine, automotive, energy, and space travel domains, composite materials have become ubiquitous because of their superior stiffness-to-weight ratios as well as corrosion and fatigue resistance. However, from a manufacturing perspective, these advanced materials have introduced new challenges that demand the development of new tools. Due to the complex anisotropic and nonlinear material properties, composite materials are more difficult to model than conventional materials such as metals and plastics. Furthermore, there exist ultra-high precision requirements in safety critical applications that are yet to be reliably met in production. Towards developing new tools addressing these challenges, this dissertation aims to (i) build high-fidelity numerical simulations of composite assembly processes, (ii) bridge these simulations to machine learning tools, and (iii) apply data-driven solutions to process control problems while identifying and overcoming their shortcomings. This is accomplished in case studies that model the fixturing, shape control, and fastening of composite fuselage components. Therein, simulation environments are created that interact with novel implementations of modified proximal policy optimization, based on a newly developed reinforcement learning algorithm. The resulting reinforcement learning agents are able to successfully address the underlying optimization problems that underpin the process and quality requirements. / Doctor of Philosophy / Within the manufacturing domain, there has been a concerted effort to transition towards Industry 4.0. To a large degree, this term refers Klaus Schwab's vision presented at the World Economic Forum in 2015, in which he outlined fundamental systemic changes that would incorporate ubiquitous computing, artificial intelligence (AI), big data, and the internet-of-things (IoT) into all aspects of productive activities within the economy. Schwab argues that rapid change will be driven by fusing these new technologies in existing and emerging applications. However, this process has only just begun and there still exist many challenges to realize the promise of Industry 4.0. One such challenge is to create computer models that are not only useful during early design stages of a product, but that are connected to its manufacturing processes, thereby guiding and informing decisions in real-time. This dissertation explores such scenarios in the context of composite structure assembly in aerospace manufacturing. It aims to link computer simulations that characterize the assembly of product components with their physical counterparts, and provides data-driven solutions to control problems that cannot typically be solved without tedious trial-and-error approaches or expert knowledge.

CubeSats, specially the 6U standard, is nowadays the tendency where many developers point towards. The upscaling size of the standard and payloads entail the increase of the satellite overall mass. Composite materials have demonstrated the ability to fulfill expectations like reducing structural masses, having been applied to different types of spacecraft, including small satellites. This Thesis is focused on designing, manufacturing, and dynamic testing of a 6U CubeSat made of carbon fiber, fiberglass, and aluminum. The main objective of this study was obtaining a mass reduction of a 6U CubeSat structure, maintaining the stiffness and strength. Considering the thermal effects of the used materials an outgassing test of the used materials was performed and the experimental results are presented. The CubeSat structure was entirely manufactured and tested at Cal Poly Aerospace Engineering Department facilities. A mechanical shock test and random vibration test were performed using a shock table and a shake table respectively. Results of both tests are presented. A correlation between the Experimental data and the Finite Element Model of the satellite was carried out. Finally, a comparison between 6U structure studied and aluminum 6U structures available in the market is presented.

A Study Of Shock Analysis Using The Finite Element Method Verified With Euler-Bernoulli Beam Theory; Mechanical Effects Due To Pulse Width Variation Of Shock Inputs; And Evaluation Of Shock Response Of A Mixed Flow Fan David Jonathan González Campos For many engineers that use finite element analysis or FEA, it is very important to know how to properly model and obtain accurate solutions for complicated loading conditions such as shock loading. Transient acceleration loads, such as shocks, are not as common as static loads. Analyzing these types of problems is less understood, which is the basis for this study. FEA solutions are verified using classical theory, as well as experimental results. The complex loading combination of shock and high speed rotation is also studied. Ansys and its graphic user interface, Workbench Version 14.5, are the programs used to solve these types of problems. Classical theory and Matlab codes, as well as experimental results, are used to verify finite element solutions for a simple structure, such as a cantilevered beam. The discrepancy of these FEA results is found to be 2.3%. The Full Method and the Mode Superposition Method in Ansys are found to be great solution tools for shock loading conditions, including complex acceleration and force conditions. The Full Method requires less pre-processing but solutions could take days, as opposed to hours, to complete in comparison with the Mode Superposition Method, depending on the 3D Model. The Mode Superposition Method requires more time and input by the user but solves relatively quickly. Furthermore, a new representation of critical pulse width of the shock inputs is presented. Experimental and finite element analyses of a complete mixed flow fan undergoing ballistic shock is also completed; deformation results due to shock loading, combined with rotation and aerodynamic loading, account for 32.3% of the total deformation seen from experimental testing. Solution methods incorporated in Ansys, and validation of FEA results using theory, have great potential implications as powerful tools for engineering students and practicing engineers.