Several free-free beam micro-resonators are designed and fabricated using two commercially available surface micromachining processes, the UW-MEMS process and PolyMUMPs. Theoretical derivations of the design parameters are presented and an electrical lumped behavior model is developed for a single resonator with direct mechanic-to-electric analogy. A finite-element analysis (FEA) tool, the COMSOL Multiphysics 4.2a, is utilized to simulate the effects of the critical structural dimensions and electromechanical coupling. A variety of analyses, such as modal, static and dynamic responses are performed in FEA and the results are compared with the analytical solutions. The static and dynamic performances of the fabricated UW-MEMS resonators are tested using the Vecco NT-9100 In-Motion System. The electrical testing is carried out to obtain the frequency characteristics in electrical domain of the device. Measured data are compared with the analytical and simulation results. Discrepancies are discussed and analyzed.

Development of foam cutting machines for rapid prototyping and manufacturing purposes began shortly after the first additive manufacturing machines became commercialised in the late 1980s. Increased computer power, the development and adoption of CAD/CAM software and rising demand for customisation has caused the rapid prototyping industry to grow swiftly in recent decades. While conventional rapid prototyping technologies are continuing to improve in speed and accuracy the ability to produce large (> 1m³) prototypes, moulds or parts it is still expensive, time consuming and often impossible. Foam cutting rapid prototyping and manufacturing machines are ideally suited to fulfil this niche because of their high speed, large working volumes and inexpensive working materials. Few foam cutting rapid prototyping machines have been commercialised to-date leaving significant opportunities for research and development in this area. Thermal plastic foam cutting is the material removal process most commonly used in foam cutting rapid prototyping to shape or sculpt the plastic foam into desired shapes and sizes. The process is achieved by introducing a heat source (generally a wire or ribbon) which alters the physical properties of the plastic foam and allows low cutting forces to be achieved. In thermal plastic foam cutting the heat source is generated via Joule (electrical) heating. This study investigates the plastic foam cutting process using experimental cutting trials and finite element analysis. The first part of this thesis presents an introduction to conventional foam cutting machines and rapid prototyping machines. It is suggested that a market opportunity lies out of reach of both of these groups of machines. By combining attributes from each, foam cutting rapid prototyping machines can be developed to fill the gap. The second part of this thesis introduces the state-of-the-art in foam cutting rapid prototyping and investigates previous research into plastic foam cutting mechanics. The third part of this thesis describes cutting trials used to determine important factors which influence plastic foam cutting. Collectively over 800 individual cutting tests were made. The cutting trials included two main material sets, expanded polystyrene and extruded polystyrene, three different wire diameters, two hot-ribbon configurations and a wide range of feed rates and power inputs. For each cut the cutting force, wire temperature and kerf width was measured as well as observations of the surface texture. The data was then analysed and empirical relationships were identified. An excel spreadsheet is established which allows the calculation of important outcomes, such as kerf width, based on chosen inputs. Quantitative measurements of the surface roughness and form, of cuts made with hot-tools, will not be addressed in this thesis. This body of work is currently under investigation by a colleague within the FAST group. The fourth part of this thesis describes the formation of a nonlinear transient two-dimensional heat transfer finite element model, which is developed for plastic foam cutting simulations. The conclusion is that the cutting trials contributed to a better understanding of plastic foam cutting mechanics. A new parameter was identified called the mass specific effective heat input, which is a function of the foam material and the cutting tool, it allows the prediction of cutting conditions with given cutting parameters and hence provides the necessary relationships needed for adaptive automated foam sculpting. Simulation results were validated by comparison with experimental data and provide a strong base for further developments including optimisation processes with adaptive control for kerf width (cut error) minimization. This study has added considerably to the pool of knowledge for foam cutting with a hot-tool. In general, much of the work reported herein has not been previously published. This work provides the most advanced study of foam sculpting work available to date.

Structural wood design standards recognize lateral torsional buckling as an important failure mode, which tends to govern the capacity of long span laterally unsupported beams. A survey of the literature indicates that only a few experimental programs have been conducted on the lateral torsional buckling of wooden beams. Within this context, the present study reports an experimental and computational study on the elastic lateral torsional buckling resistance of wooden beams. The experimental program consists of conducting material tests to determine the longitudinal modulus of elasticity and rigidity modulus followed by a series of 18 full-scale tests. The buckling loads and mode shapes are documented. The numerical component of the study captures the orthotropic constitutive properties of wood and involves a sensitivity analysis on various orthotropic material constants, models for simulating the full-scale tests conducted, a comparison with experimental results, and a parametric study to expand the experimental database. Based on the comparison between the experimental program, classical solution and FEA models, it can be concluded that the classical solution is able to predict the critical moment of wood beams. By performing the parametric analysis using the FEA models, it was observed that loads applied on the top and bottom face of a beam decrease and increase its critical moment,respectively. The critical moment is not greatly influenced by moving the supports from mid-span to the bottom of the end cross-section.

Vehicle anti-roll bars are suspension components used for limiting body roll angle. They have a direct effect on the handling characteristics of the vehicle. Design changes of anti-roll bars are quite common at various steps of vehicle production, and a design analysis must be performed for each change. Finite Element Analysis (FEA) can be effectively used in design analysis of anti-roll bars. However, due to high number of repeated design analyses, the analysis time and cost problems associated with the use of general FEA package programs may create considerable disadvantages in using these package programs for performing anti-roll bar design analysis. In this study, an automated design program is developed for performing design analysis of vehicle anti-roll bars. The program is composed of two parts, the user interface and the FEA macro. The FEA macro includes the codes for performing deformation, stress, fatigue, and modal analysis of anti-roll bars in ANSYS 7.0. The user interface, which is composed in Visual Basic 6.0, includes the forms for data input and result output procedures. By the developed software, the FEA of the anti-roll bars is simplified to simple data entry via user interface. The flow of the analysis is controlled by the program and the finite element analysis is performed by ANSYS at the background. The developed software can perform design analysis for a wide range of anti-roll bars: The bar centerline can have any 3D shape, the cross section can be solid or hollow circular, the end connections can be of pin or spherical joint type, the bushings can be mounted at any position on the bar with a user defined bushing length. The effects of anti-roll bar design parameters on final anti-roll bar properties are also evaluated by performing sample analyses with the automated design program developed in this study.

AN ABSTRACT OF THE THESIS OF Olanrewaju Ari Adeniyi for the Master of Science degree in Mechanical Engineering and Energy Processes presented June 2012, at Southern Illinois University Carbondale Title: FUSION OF ULTRASONIC C-SCAN DATA WITH FINITE ELEMENT ANALYSIS Major Professor: Dr. Tsuchin Philip Chu Ultrasonic testing is a highly valued method in the field of Non-destructive testing (NDT). It is an engineering tool that allows for non-invasive testing and evaluation. It is used widely in the aerospace industry to determine the integrity of complex materials without the use of destructive measures. This method of testing can be utilized to provide multitude of parameters such as material properties and thicknesses. It can also be used to test for discrepancies in test specimen such as voids, impurities, delamination and other defects that could degrade the integrity of a structure. The problem is that this method is limited in the area of evaluation of end results. Results are generated in the form of data images and are evaluated for quality or quantitative image assessment. Simulation models are created from an image, which causes low accuracy of analysis. The integration of Ultrasonic C-scan data with Finite Element Analysis (FEA) addresses these issues. It allows for models to be generated from Ultrasonic C-scan data, which provides the means to conduct accurate FEA simulations. The fusion of Ultrasonic C-scan data with computational methods, such as FEA, allows tested materials to be subjected to loading conditions that may be experienced in actual use. The results from FEA analysis can provide localized stress and strain fields generated from the loading conditions. The success of this analysis relies on the ability to generate high quality C-scan data to create accurate CAD data models. The generation of high quality scans will produce vital analysis information such as material properties, thickness, voids, surface inclusions and other critical deformities, all which will be used to generate a CAD analysis. With the ultrasonic data generated, finite element analysis can be utilized to further evaluate tested specimen. This technique has been applied to an isotropic aluminum block standard and an anisotropic Carbon Fiber Reinforced Polymer sample, both with known defects.

Doctor of Philosophy / Department of Industrial & Manufacturing Systems Engineering / Zhijian Pei / Silicon is the primary semiconductor material used to fabricate integrated circuits (ICs). The quality of integrated circuits depends directly on the quality of silicon wafers. A series of processes are required to manufacture the high-quality silicon wafers. Chemical mechanical polishing is currently used to manufacture the silicon wafers as the final material removal process to meet the ever-increasing demand for flatter wafers and lower prices. A finite element analysis has been conducted to study the effects of influencing factors (including Young's modulus and Poisson's ratio of the polishing pad, thickness of the pad, and polishing pressure) on the wafer flatness. In addition, an experimental study was carried out on the effects of process variables (including wafer rotation speed, pad rotation speed, the temperature of the cooling wafer in polishing table, polishing pressure, and the slurry flow rate) on material removal rate (MRR) in polishing of silicon wafers. The results from this study show that the polishing pressure and the pad speed are the most significant factors affecting the MRR. The polishing pad is one of the most critical factors in planarizing the wafer surface. It transports the slurry and interacts with the wafer surface. When the number of polished wafers increases, the pad is glazed and degraded and hence the polishing quality is decreased. The pad properties are changed during the process. The measuring methods for the pad properties including pad thickness monitoring, elastic properties and hardness are reviewed. Elasticity of two types of pads are measured and compared. The poor flatness problems such as tapering, edge effect, concave or convex wafer shape were investigated. Finite element models were developed to illustrate the effects of polishing pad and carrier film properties on the stress and contact pressure distribution on the wafer surface. Moreover, the material removal unevenness is studied. A grinding-based manufacturing method has been investigated experimentally to demonstrate its potential to manufacture flat silicon wafers at a lower cost. It has been demonstrated that the site flatness on the ground wafers (except for a few sites at the wafer center) could meet the stringent specifications for future silicon wafers. One of the problems is the poor flatness at the wafer center: central dimples on ground wafers. A finite element model is developed to illustrate the generation mechanisms of central dimples. Then, effects of influencing factors (including Young's modulus and Poisson's ratio of the grinding wheel segment, dimensions of the wheel segment, grinding force, and chuck shape) on the central dimple sizes are studied. Pilot experimental results are presented to substantiate the predicted results from the finite element model. This provides practical guidance to eliminate or reduce central dimples on ground wafers. The study in this thesis is to understand the mechanism of CMP and grinding of silicon wafers. Improving the processes and the quality of silicon wafers are the final goals.

The main aim of this project was to examine the effects of introducing hierarchy into honeycombs and determining the variables that preside over the global response of the structure. Specifically to understand how the in and out-of-plane elastic and non-linear plastic properties of honeycombs were affected by hierarchy. Analytical analysis of hierarchical honeycombs has been used to explain and predict the response of finite element simulations validated by experimental investigations. The early stage of the investigation focused on finding if the elastic modulus could be maintained or improved on an equal density basis due to the introduction of hierarchy. It is clear that honeycombs are sensitive to hierarchical sub-structures, particularly the fraction of mass shared between the super-and sub-structures. Introduction of an additional level of hierarchy without reducing performance is difficult, but was possible by functional grading. Another original result was that it was determined when the sub-structure could be assumed to be a continuum of the super-structure. Meaning the material properties from a single unit sub-cell could be used as the constituent material properties of the super-structure, as in previous work by (Lakes 1993) and (Carpinteri et al 2009) for example. Work investigating the in-plane, non-linear plastic response of hierarchical honeycombs showed that the introduction of hierarchy into honeycombs can have the effect of delaying the onset of elastic buckling, which is a common failure mechanism for low relative density structures. As such it was possible to achieve a marked increase in the recoverable energy absorbed by hierarchical honeycombs prior to elastic buckling or plastic yield. The potential benefits are less apparent in higher relative density structures due to the onset of plasticity becoming the first mode of failure. The out-of-plane properties also investigated showed no increase in the elastic properties due to the introduction of hierarchy, but showed a marked increase in the out-of-plane elastic buckling stress of 60% when compared to a conventional hexagonal honeycomb of the same relative density.

Increasing the power density of the DC-DC converters requires the size and weight of the magnetic components, such as inductors and transformers, to be reduced. In this thesis, the losses in nanocrystalline inductor cores are characterised and analysed, including the traditional core loss and the gap loss caused by the air gap fringing flux. The loss calculations will form a basis for the design and optimisation of high power inductors for DC-DC converters for EV applications. This thesis first characterises experimentally the core losses in four nanocrystalline cores over a range of operating conditions that are representative of those encontered in typical high power converter applications, including non-sinusoidal waveforms and DC bias conditions. The core losses are assessed by the measured B-H loops and are characterised as a function of DC flux density, showing that for a fixed AC induction level, the losses can vary by almost an order of magnitude as the DC bias increases and the duty ratio moves away from 0.5. The results provide a more complete picture of the core loss variations with both DC and AC magnetisations than is available in manufactures’ data sheets. An electromagnetic finite element (FE) model is used to examine the gap loss that occurs in finely laminated nanocrystalline cores under high frequency operation. The loss is significant in the design example, contributing to almost half of the total inductor loss, and the gap loss is highly concentrated in the region of the air gap. The dependence of the gap loss on key inductor design parameters and operating condtions is also explored. An empirical equation is derived to provide a design-oriented basis for estimating gap losses. Thermal finite element analysis is used to estimate the temperature rise and identify the hot spot in a nanocrystalline inductor encapsulated in an alumimium case. The temperature distribution in the core largely corresponds to the non-uniform distribution of the gap loss. The thermal FEA can also be used to evaluate different thermal management methods to optimise the design for a more compact component. The FE modelling of gap loss and the thermal predictions are validated experimentally on a foil-wound Finemet inductor, showing good agreement between the predictions and measurements under various operating conditions.

Structural wood design standards recognize lateral torsional buckling as an important failure mode, which tends to govern the capacity of long span laterally unsupported beams. A survey of the literature indicates that only a few experimental programs have been conducted on the lateral torsional buckling of wooden beams. Within this context, the present study reports an experimental and computational study on the elastic lateral torsional buckling resistance of wooden beams. The experimental program consists of conducting material tests to determine the longitudinal modulus of elasticity and rigidity modulus followed by a series of 18 full-scale tests. The buckling loads and mode shapes are documented. The numerical component of the study captures the orthotropic constitutive properties of wood and involves a sensitivity analysis on various orthotropic material constants, models for simulating the full-scale tests conducted, a comparison with experimental results, and a parametric study to expand the experimental database. Based on the comparison between the experimental program, classical solution and FEA models, it can be concluded that the classical solution is able to predict the critical moment of wood beams. By performing the parametric analysis using the FEA models, it was observed that loads applied on the top and bottom face of a beam decrease and increase its critical moment,respectively. The critical moment is not greatly influenced by moving the supports from mid-span to the bottom of the end cross-section.

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.