Printed Circuit Boards (PCBs) are a ubiquitous element of virtually every electronic system manufactured world-wide. It is not a stretch of the imagination to say that if it’s electronic, there is a PCB in it. PCBs are necessary tools for electronics work, and tools need to have instructions. For better or worse, PCB knowledge is a deep and wide ocean. There is much to cover for even a surface level understanding, and there are deep areas rich in technical expertise. Navigating the ocean of knowledge is treacherous; common knowledge of yore can be downright dubious now. PCB manufacturing and electronics as a whole have seen incredible developments in the past few decades, and knowledge once true may be outdated. At the same time there is a downpour of new techniques to use and challenges to face. The storm of information deepens the sea and can make it seem impossible to get anywhere without getting utterly lost. There are islands of knowledge out there hiding in books and papers and websites, but no guide to get anywhere. This thesis aims to guide the reader through the sea of information and provides a map that charts the shallows of beginner knowledge, into the deep depths of advanced design, of how and where to learn more. This thesis serves as an aiding means through the exciting and vast world of PCB design and layout.

Multi-material 3D Printing allows the ability to fabricate parts with tuned mechanical properties, multi-process 3D printing widens the choices of available fabrication materials. The objective of this study is to build a custom 3D printing test bed that is capable of printing multi-material parts with fused deposition modeling and direct ink writing techniques. A 3D printer, controlled by an industrial motion control system, with FDM and DIW capabilities was built by combining FDM extruders with a pneumatic dispensing system on a single platform. By utilizing the Direct Ink Writing function, we expand the number of printable materials to include some off the shelf silicones and epoxies, as well as custom, user made, materials. This study will further expand the manufacturing and research capabilities within the additive manufacturing discipline.

The future of aerospace has long been dedicated to making airplanes more lightweight and faster than ever before. Automation is essential to achieve these goals while maintaining a standard of consistency and quality. The overall goal of this research is to develop an automated piece of equipment that can effectively laminate a contoured composite layup at a rapid pace in order to compete with alternative options. In this study, the equipment and its components were designed and first evaluated through computational modeling and simulation. Then a prototype of the developed equipment was built for experimental testing and validating. The manufactured equipment was applied to form laminate sheets with different contours, ramp rates, and thicknesses. The forming speed and quality of the formed laminate sheets were assessed to validate the developed equipment.

This study is devoted to some of the most important issues for advancing inkjet printing for possible application in the coating industry with a focus on piezoelectric droplet on demand (DOD) inkjet technology. Current problems, as embodied in liquid filament breakup along with satellite droplet formation and reduction in droplet sizes, are discussed and then potential solutions identified. For satellite droplets, it is shown that liquid filament break-up behavior can be predicted by using a combination of two pi-numbers, including the Weber number, We and the Ohnesorge number, Oh, or the Reynolds number, Re, and the Weber number, We. All of these are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria are shown to have merit in comparison to currently used criteria for identifying filament physical features such as length and diameter that control the formation of subsequent droplets. In addition, this study performs scaling analyses for the design and operation of inkjet printing heads. Because droplet sizes from inkjet nozzles are typically on the order of nozzle dimensions, a numerical simulation is carried out to provide insight into how to reduce droplet sizes by employing a novel input waveform impressed on the print-head liquid inflow without changing the nozzle geometry. A regime map for characterizing the generation of small droplets based on We and a non-dimensional frequency, Ω is proposed and discussed. In an attempt to advance inkjet printing technology for coating purposes, a prototype was designed and then tested numerically. The numerical simulation successfully proved that the proposed prototype could be useful for coating purposes by repeatedly producing mono-dispersed droplets with controllable size and spacing. Finally, the influences of two independent piezoelectric characteristics - the maximum head displacement and corresponding frequency, was investigated to examine the quality of filament breakup quality and favorable piezoelectric displacements and frequencies were identified.

Highway roughness is a concern for both the motoring public and highway authorities. Roughness may even increase the risk of crashes. Rail-highway grade crossings are particularly problematic. Roughness may be due to deterioration or simply due to the way the crossing was built to accommodate grade change, local utilities, or rail elevation. With over 216,000 crossings in the US, maintenance is a vast undertaking. While methods are available to quantify highway roughness, no method exists to quantitatively assess the condition of rail crossings. Conventional inspection relies on a labor-intensive process of qualitative judgment. A quantifiable, objective and extensible procedure for rating and prioritizing improvement of crossings is thus desired. In this dissertation, a 3D infrastructure condition assessment model is developed for evaluating the condition and performance of rail highway grade crossings. Various scanning techniques and devices are developed or used to obtain the 3D “point cloud” or surface as the first step towards quantifying crossing roughness. Next, a technique for repeatable field measurement of acceleration is presented and tested to provide a condition index. Acceleration-based metrics are developed, and these can be used to rate and compare crossings for improvement programs to mitigate potential vehicle damage and provide passenger comfort. A vehicle dynamic model is next customized to use surface models to estimate vertical accelerations eliminating the need for field data collection. Following, crossing roughness and rideability is estimated directly from 3D point clouds. This allows isolation of acceleration components derived from the surface condition and original design profile. Finally, a practice ready application of the 3D point cloud is developed and presented to address hump crossing safety. In conclusion, the dissertation presents several methods to assess the condition and performance of rail crossings. It provides quantitative metrics that can be used to evaluate designs and construction methods, and efficiently implement cost effective improvement programs. The metrics provide a technique to measure and monitor system assets over time, and can be extended to other infrastructure components such as pavements and bridges.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: A wide variety of design methodologies exist in literature and the methodologies employed may differ among companies and even among design teams. Therefore a software tool, called DiDeas II, is being developed for the early phases of mechanical engineering design. DiDeas II is customisable to accommodate various design methodologies. An approach for customisability which allows the user interface and data structure to be customised without changing the source code has been implemented in previous developments via an approach combining ontology and conceptual graphs. This approach is expanded in this thesis to allow for the implementation of various design methodologies through the use of tables for the display of information with inheritance of data among these tables. During groupwork, communication is both asynchronous and synchronous. DiDeas II has been developed in this thesis to facilitate and capture both asynchronous and synchronous communication between team members. Capturing such communications has the potential to provide insight into design decisions. The communication functionality was assessed in case studies in an academic environment. DiDeas II proved to be effective at recording “soft” information during design and placing the information into context for future reference. The degree to which DiDeas II could be customised to suit the design process at different companies was assessed through discussions with engineers in industry. These discussions showed that it was possible to customise DiDeas II according to the design processes followed by the participants. / AFRIKAANSE OPSOMMING: „n Wye verskeidenheid ontwerpsmetodologieë bestaan in die literatuur en die metodologieë wat gebruik word kan tussen maatskappye en selfs tussen ontwerpspanne verskil. Daarom word „n sagteware-hulpmiddel, genaamd DiDeas II, ontwikkel vir die vroeë fases van meganiese ingenieursontwerp. DiDeas II is pasbaar om voorsiening te maak vir verskeie ontwerpsmetodologieë. „n Benadering vir pasbaarheid wat toelaat dat die gebruikerskoppelvlak en datastruktuur aangepas kan word sonder om veranderings aan die bron-kode te maak, is geïmplementeer in vorige ontwikkelings deur „n benadering wat ontologie en konseptuele grafieke kombineer. Hierdie benadering is in hierdie tesis uitgebrei om voorsiening te maak vir die implementering van verskeie ontwerpsmetodologieë d.m.v. tabelle vir die vertoon van informasie, met data wat “oorgeërf” word tussen hierdie tabelle. Kommunikasie is beide asinkroon en sinkroon tydens groepwerk. DiDeas II is in hierdie tesis verder ontwikkel om beide asinkrone en sinkrone kommunikasie metodes te bemiddel en daarvan rekord te hou. Die rekordhouding van sulke kommunikasie het die potensiaal om insig te bied aangaande ontwerpbesluite. Die kommunikasie funksionaliteit is geassesseer in gevallestudies in „n akademiese omgewing. DiDeas II was effektief in die rekordhouding van “sagte” informasie tydens ontwerp, sowel as om sulke informasie binne konteks te plaas vir latere verwysing. Die mate waartoe DiDeas II aangepas kan word om voorsiening te maak vir die ontwerpsprosesse van verskillende maatskappye, is geassesseer deur gesprekke met ingenieurs in industrie. Hierdie gesprekke het getoon dat dit moontlik is om DiDeas II aan te pas volgens die ontwerpsprosesse wat die deelnemers gebruik.

Piezoelectric materials in the forms of both bulk and thin-film have been widely used as actuators and sensors due to their electromechanical coupling. The characterization of piezoelectric materials plays an important role in determining device performance and reliability. Instrumented indentation is a promising method for probing mechanical as well as electrical properties of piezoelectric materials. The use of instrumented indentation to characterize the properties of piezoelectric materials requires analytical relations. Finite element methods are used to analyze the indentation of piezoelectric materials under different mechanical and electrical boundary conditions. For indentation of a piezoelectric half space, a three-dimensional finite element model is used due to the anisotropy and geometric nonlinearity. The analysis is focused on the effect of angle between poling direction and indentation-loading direction on indentation responses. For the indentation by a flat-ended cylindrical indenter, both insulating indenter and conducting indenter without a prescribed electric potential are considered. The results reveal that both the indentation load and the magnitude of the indentation-induced potential at the contact center increase linearly with the indentation depth. For the indentation by an insulating Berkovich indenter, both frictionless and frictional contact between the indenter and indented surface are considered. The results show the indentation load is proportional to the square of the indentation depth, while the indentation-induced potential at the contact center is proportional to the indentation depth. Spherical indentation of piezoelectric thin films is analyzed in an axisymmetric finite element model, in which the poling direction is anti-parallel to the indentation-loading direction. Six different combinations of electrical boundary conditions are considered for a thin film perfectly bonded to a rigid substrate under the condition of the contact radius being much larger than the film thickness. The indentation load is found to be proportional to the square of the indentation depth. To analyze the decohesion problem between a piezoelectric film and an elastic substrate, a traction-separation law is used to control the interfacial behavior between a thin film and an electrically grounded elastic substrate. The discontinuous responses at the initiation of interfacial decohesion are found to depend on interface and substrate properties.

The United States holds the world's largest estimated reserves of coal and is also a net exporter of it. Coal gasification provides a cleaner way to utilize coal than directly burning it. Gasification is an incomplete oxidation process that converts various carbon-based feedstocks into clean synthetic gas (syngas), which can be used to produce electricity and mechanical power with significantly reduced emissions. Syngas can also be used as feedstock for making chemicals and various materials. A Computational Fluid Dynamics (CFD) scheme has been used to simulate the gasification process for many years. However, many sub-models still need to be developed and improved. The objective of this study is to use the improved CFD modeling to understand the thermal-flow behavior and the gasification process and to provide guidance in the design of more efficient and cheaper gasifiers. Fundamental research has been conducted to improve the gasification sub-models associated with the volatile thermal cracking, water-gas-shift (WGS) reaction, radiation effect, low-rank-coal gasification, coal to synthetic-natural-gas (SNG), and ash deposition mechanisms. The improved volatile thermal cracking model includes H2S and COS contents. A new empirical WGS reaction model is developed by matching the result with experimental data. A new coal demoisturization model is developed for evaporating the inherent moisture inside the coal particles during low-rank-coal gasification. An ash deposition model has also been developed. Moreover, the effect of different radiation models on the simulated result has been investigated, and the appropriate models are recommended. Some improved model tests are performed to help modify an industrial entrained-flow gasifier. A two-stage oxygen feeding scheme and a unique water quench design are investigated. For the two-stage oxygen feeding design, both experimental data and CFD predictions verify that it is feasible to reduce the peak temperature and achieve a more uniform temperature distribution in the gasifier by controlling the injection scheme without changing the composition and production rate of the syngas. Furthermore, the CFD simulation can acceptably approximate the thermal-flow and reaction behaviors in the coal gasification process, which can then be used as a preliminary screening tool for improving existing gasifiers’ performance and designing new gasifiers.

Os métodos de geração de malhas são essenciais para simulações numéricas de engenharia. Simulações estruturais pelo método dos elementos finitos (MEF) dependem diretamente das malhas que representam as geometrias às quais são impostos os carregamentos e parte importante da precisão dos cálculos é devida à qualidade da malha. Há uma vasta variedade de métodos e algoritmos para gerar malhas computacionais direcionadas à aplicação do MEF, mas nem todos abrangem geometrias genéricas ou irregulares. Figuras irregulares com regiões curvas e vazios internos requerem o uso de algoritmos específicos, ou genéricos o suficiente, de modo que sejam capazes de processar suas particularidades geométricas, gerando elementos de boa qualidade. Este trabalho propõe uma investigação dos métodos geradores de malhas que tratem as geometrias frequentemente apresentadas nas seções transversais dos componentes dos cabos umbilicais e tubos flexíveis, selecionando criteriosamente aquele que mais se adapte às necessidades geradas pela aplicação do MEF nestas geometrias. Foi realizada uma breve revisão do estado da arte dos métodos geradores de malhas bidimensionais partindo das revisões já publicadas e de artigos explicando versões de algoritmos, seguindo os trabalhos encontrados na literatura. São formulados os critérios de seleção de métodos geradores de malha e de trabalhos encontrados baseando-se nas características. Ao final, o Método de Pavimentação foi selecionado e, a partir de sua implementação computacional, foi desenvolvido o GreenMesh, um programa de computador gerador de malhas utilizando figuras dadas como entrada. Foram geradas várias malhas a partir das geometrias típicas dos equipamentos aqui focados e com isso foi verificado o uso do algoritmo para este fim. / Computational mesh generation methods are essential for engineering numerical simulation. Structural simulations by the finite element method (FEM) rely straightly of meshes that represent the geometries on which the loads are imposed. They are very important for the calculus precision because the mesh quality influences the results. There is a vast variety of computational mesh generation methods and algorithms aimed to FEM analysis, but not all handles generic and irregular geometries. Irregular figures formed by curved regions and internal void requires the use of specific algorithms, or sufficiently generic, in a way that they can process geometric particularities, generating good quality elements. This work proposes an investigation of mesh generation methods that handle frequently presented geometries in cross sections of umbilical cable and flexible pipes internal components, selecting judiciously the method that best suits the necessities generated by the application of FEM analysis on theses geometries. A brief survey about the state of the art of bidimensional mesh generation methods was performed, starting from already published reviews and from articles explaining versions of algorithms, accordingly to the material found in the literature. Finally, the Paving Method has been selected and, starting from its computational implementation, it has been developed GreenMesh, a computer program to generate meshes using given figures as input. It has been generated many meshes from typical geometries of the aimed equipments and that verified the use of the algorithm to this purpose.

The objective of this whole study was to evaluate a LiDAR sensor for high-resolution remote sensing in agriculture. A linear motion system was developed to precisely control the dynamics of LiDAR sensor in effort to remove uncertainty in the LiDAR position/velocity while under motion. A user control interface was developed to operate the system under different velocity profiles and log LiDAR data synchronous to the motion of the system. The LiDAR was then validated using multiple test targets with five different velocity profiles to determine the effect of sensor velocity and height above a target on measurement error. The results indicated that the velocity of the LiDAR was a significant factor affecting the error and standard deviation of the LiDAR measurements, although only by a small margin. Then the concept of modeling the alfalfa using the linear motion system was introduced. Two plots of alfalfa were scanned and processed to extract height and volume and was compared with photogrammetric and field measurements. Insufficient alfalfa plots were scanned which prevented any statistical analysis from being used to compare the different methods. However, the comparison between LiDAR and photogrammetric data showed some promising results which may be further replicated in the future.