The Formula SAE is a student based competition organised by SAE International where engineering students from a university design, develop and test a formula-style race car prototype to compete against other universities. The competition car needs to satisfy the competition rules set out by the organisers. The competition strives to stimulate original, creative problem solving together with innovative engineering design practices. In any race environment, the primary goal is always to be as competitive as possible. Due to the competitive nature of motor sport, vehicle components need to withstand various and severe stresses. The components of a race car vehicle are responsible for the vehicle’s handling characteristics and reliability. The chassis is a crucial and integral component of a Formula SAE competition car, primarily responsible for the vehicle’s performance characteristics. The chassis is the structural component that accommodates all the other components. A Formula SAE chassis is a structure that requires high torsional stiffness, low weight as well as the necessary strength properties. In this study, multiple Formula SAE chassis were designed and developed using computer aided design software. Each concept’s torsional stiffness, weight and strength properties were tested using finite element analysis software. The different concepts consisted of different design techniques and applications. All the concepts were analysed and assessed, leading to the identification of an acceptable prototype. The prototype was manufactured for experimental tests. The designed chassis complied with the Formula SAE rules and regulations. The weight, torsional stiffness and strength characteristics of the designed chassis frame were also favourable compared to accepted standards for Formula SAE chassis frames. The manufactured chassis was prepared for experimental tests in order to validate the simulation results produced by the finite element analysis. The torsional stiffness, weight and strength were experimentally determined and the results were compared with the corresponding simulations results. The comparison of the experimental and simulated results enabled the validation of the finite element analysis software. The study draws conclusions about the use of computer aided design and finite element analysis software as a design tool for the development of a Formula SAE chassis. Closure about the study is provided with general conclusions, recommendations and research possibilities for future studies. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

In the process of engine design, it is important for the engine designer to predict the accurate component temperatures. Controlling the temperature of engine components requires a better understanding of the coolant behaviour in the coolant jacket of an engine which is critical to internal combustion engine design, The studies reported in the literature emphasize the influence of the cooling system on other engine operation such as exhaust emission, fuel consumption and engine wear. In this context, much work has been done with the purpose of improving the coolant jacket design and components of the cooling system to achieve higher performance. (Some of these studies) Previous researches have shown the possibility of achieving higher engine efficiency and performance with higher coolant temperature. This project aims at understanding the coolant flow behaviour in the coolant jackets of a diesel engine and investigating the possibility of running the engine at higher coolant temperatures by predicting the temperature distribution of the structure which is required for the assessment of the durability ofthe engine components. In this thesis, CFD (Computational Fluid Dynamics) and FE (Finite Element) techniques are used to study coolant flow in the coolant jackets and to predict the temperature distribution within the engine structure respectively. The objectives are to develop an FE model of the engine structure for thermal analyses and a CFD model of the fluid domain for the coolant flow CFD analyses. A number of case studies are carried out with the purpose of determining the most suitable technique for accurate temperature prediction. The methodology of manual coupling approach between CFD and FE analyses, which is more widely used in industry, and conjugate approach are demonstrated. Using these approaches, thermal analysis of the engine is conducted with the purpose of identifying the thermally critical locations throughout the engine. Furthermore, the influences of higher coolant temperature on these thermally critical regions of the engine are highlighted by carrying out four case studies with coolant inlet temperatures of 110°C, !ISOC, 117.5"C and !20°C. The temperature rise at the particular points around thermally critical regions is found to be in the range of 3-9 degrees at the higher coolant temperatures. This slight increase in temperature of critical locations may affect the durability of the structure. However, without carrying out the structural analyses it is not possible to comment on the durability of the engine structure. The effects of surface roughness and viscosity on heat transfer rate are also investigated and shown to be insignificant.

Adhesive bonding is one of the most attractive joining techniques for any structural application, including high profile examples in the aerospace, automotive, marine construction and electrical industries. Advantages of adhesive bonding include; superior fatigue performance, better stress distribution and higher stiffness than conventional joining techniques. When the design of bonded joints is considered, fatigue is of critical importance in most structural applications. There are two main issues that are of importance; a) in-service damage characterisation during fatigue loading and, b) lifetime prediction under both constant and variable amplitude fatigue loading. If fatigue damage characterisation is considered, there has been some work to characterise damage in-situ using the backface strain (BFS) measurement technique, however, there has been little investigation of the effects of different types of fatigue behaviour under different types of geometry and loading. Regarding fatigue lifetime prediction of bonded joints, most of the work in the literature is concentrated with constant amplitude fatigue, rather than variable amplitude fatigue. Fatigue design of a bonded structure based on constant amplitude fatigue, when the actual loading on the structure is of the variable amplitude fatigue, can result in erroneous lifetime prediction. This is because of load interaction effects caused by changes in load ratio, mean load etc., which can decrease the fatigue life considerably. Therefore, the project aims to a) provide a comprehensive study of the use of BFS measurements to characterise fatigue damage, b) develop novel techniques for predicting lifetime under constant amplitude fatigue and c) provide an insight into various types of load interaction effects. In this project, single lap joints (SLJ) and compound double cantilever beam geometries were used. Compound double cantilever beams were used mainly to determine the critical strain energy release rate and to obtain the relationship between strain energy release rate and fatigue crack growth rate. The fatigue life of SLJs was found to be dominated by crack initiation at lower fatigue loads. At higher fatigue loads, fatigue life was found to consist of three phases; initiation, stable crack propagation and fast crack growth. Using these results, a novel damage progression model was developed, which can be used to predict the remaining life of a bonded structure. A non-linear strength wearout model (NLSWM) was also proposed, based on strength wearout experiments, where a normalised strength wearout curve was found to be independent of the fatigue load applied. In this model, an empirical parameter determined from a small number of experiments, can be used to determine the residual strength and remaining life of a bonded structure. A fracture mechanics approach based on the Paris law was also used to predict the fatigue lifetime under constant amplitude fatigue. This latter method was found to under-predict the fatigue life, especially at lower fatigue loads, which was attributed to the absence of a crack initiation phase in the fracture mechanics based approach. A damage mechanics based approach, in which a damage evolution law was proposed based on plastic strain, was found to predict the fatigue life well at both lower and higher fatigue loads. This model was able to predict both initiation and propagation phases. Based on the same model, a unified fatigue methodology (UFM) was proposed, which can be used to not only predict the fatigue lifetime, but also various other fatigue parameters such as BFS, strength wearout and stiffness wearout. The final part of the project investigated variable amplitude fatigue. In this case, fatigue lifetime was found to decrease, owing to damage and crack growth acceleration in various types of variable amplitude fatigue loading spectra. A number of different strength wearout approaches were proposed to predict fatigue lifetime under variable amplitude fatigue loading. The NLSWM, where no interaction effects were considered was found to over-predict the fatigue life, especially at lower fatigue loads. However, approaches such as the modified cycle mix and normalised cycle mix approaches were found to predict the fatigue life well at all loads and for all types of variable amplitude fatigue spectra. Progressive damage models were also applied to predict fatigue lifetime under variable amplitude fatigue loading. In this case a fracture mechanics based approach was found to under-predict the fatigue life for all types of spectra at lower loads, which was established to the absence of a crack initiation phase in this method. Whereas, a damage mechanics based approach was found to over-predict the fatigue lifetime for all the types of variable amplitude fatigue spectra, however the over- prediction remained mostly within the scatter of the experimental fatigue life data. It was concluded that, the damage mechanics based approach has potential for further modification and should be tested on different types of geometry and spectra.

Die Finite Elemente Analyse (FEA) ist aus heutiger Sicht aus dem Produktentwicklungsprozess nicht mehr wegzudenken. Zur Sicherstellung einer kontinuierlich wachsenden Innovationskraft sind viele kleine und mittelständische Unternehmen auf einen wirtschaftlichen Einsatz der FEA angewiesen, weshalb diese vermehrt auf Freeware Programme (z.B. Z88Aurora) zurückgreifen. Die dabei meist verwendete, linear statische Analyse von Einzelkomponenten gehört deshalb bei heutigen Simulationsaufgaben längst zum Tagesgeschäft. Diese isolierte Betrachtung von einzelnen Bauteilen ist allerdings oftmals aufgrund der fehlenden Interaktion mit benachbarten Komponenten nicht realitätsnah, weshalb komplexe numerische Simulationen von Baugruppen herangezogen werden müssen. Die Abbildung der gegenseitigen Wechselwirkung entspricht dabei einer nichtlinearen Randbedingung, da sich der Zustand zwischen den Kontaktzonen (offen oder geschlossen) während des Rechenlaufes ändern kann. Dieser technisch-physikalische Effekt lässt sich in nahezu jedem technischen System – beispielsweise einer Zahnradpaarung, einem Kettentrieb, usw. – beobachten, weshalb dessen Berücksichtigung für die Ergebnisgüte eine große Rolle spielt. Das hierfür in Z88Aurora implementierte Kontaktmodul erlaubt dem Anwender ebendiese Anbindung des elastischen Umfeldes sowie eine Detailbetrachtung der Verbindungsstelle (Kontaktdruck). Die für den industriellen Einsatz essentielle Validität der Berechnungsergebnisse wird anhand analytisch berechenbarer Geometrien, wie etwa einem Zugstab, nachgewiesen. Zusätzlich werden die Benchmark-Tests von der National Agency for Finite Element Methods and Standards (NAFEMS) sowie der Kontakt Patch-Test nach Bathe herangezogen, um die Leistungsfähigkeit und Stabilität des Z88-Kontaktalgorithmus zu erproben. Hierbei wird unabhängig von der Ausprägung des Kontaktabstands und der Oberflächenvernetzung der Bauteile die korrekte Finite-Elemente-Kontaktanalyse anhand der Homogenität der Kontaktdruckverteilung bewertet. Auf Basis dieser Benchmark-Tests und weiterführender Vergleichsrechnungen mit kommerziellen FE-Systemen zeigt sich, dass die Ergebnisse des Kontaktmoduls von Z88Aurora valide sind und die Software für den produktiven Einsatz in der Industrie geeignet ist.

High-speed craft are in high demand in the maritime industry, for example, in maintenance operations for offshore structures, for search and rescue, for patrolling operations, or as leisure craft to deliver speed and excitement. Design and operation of high-speed craft are often governed by the hydrodynamic phenomena of slamming, which occur when the craft impact the wave surface. Slamming loads affect the high-speed craft system; the crew, the structure and various sub-systems and limit the operation. To meet the ever-increasing demands on safety, economy and reduced environmental impact, there is a need to develop more efficient high-speed craft. This progression is however limited by the prevailing semi-empirical design methods for high-speed planing craft structures. These methods provide only a basic description of the involved physics, and their validity has been questioned. This thesis contributes to improving the conditions for designing efficient highspeed craft by focusing on two key topics: evaluation and development of the prevailing design methods for high-speed craft structures, and development towards structural design based on first principles modeling of the slamming process. In particular a methodological framework that enables detailed studies of the slamming phenomena using numerical simulations and experimental measurements is synthesized and evaluated. The methodological framework involves modeling of the wave environment, the craft hydromechanics and structural mechanics, and statistical characterization of the response processes. The framework forms the foundation for an extensive evaluation and development of the prevailing semi-empirical design methods for high-speed planing craft. Through the work presented in this thesis the framework is also shown to be a viable approach in the introduction of simulation-based design methods based on first principles modeling of the involved physics. Summarizing, the presented methods and results provide important steppingstones towards designing more efficient high-speed planing craft. / <p>QC 20160907</p>

No description available.

This research sought to establish residual stress distribution characteristics in typical pipe and vessel welds by carrying out a comprehensive parametric study using an advanced sequentially coupled thermo-mechanical finite element procedure. The parametric study covered vessel and pipe components with a ranging radius to thickness ratio from r/t=2 to 100, for thickness ranging from t=1/4” to 10”. Component materials varied from low carbon steel to high alloy steels, such as stainless steel and titanium alloy. Furthermore, a structural mechanics based framework is proposed to generalize through-thickness residual stress distributions for a broad spectrum of joint geometry and welding conditions. The results of this study have been shown to provide both a significantly improved understanding of important parameters governing residual stresses in pipe and vessel welds, as well as a unified scheme for achieving consistent residual stress prescriptions for supporting fitness-for-service assessments of engineering structures. Specific contributions of this investigation may be summarized as follows: (a) A welding heating input characterization procedure has been developed and validated to relate prescribed temperature thermal modeling procedure to conventional linear input definition. With this development, a large number of parametric analyses can be carried in a cost-effective manner without relying on the heat flux based weld pool model that can be exhaustive and time-consuming. (b) A set of governing parameters controlling important residual stress distribution characteristics regardless of joint types, materials, and welding procedures have been identified. These are characteristic heat input intensity and radius over thickness ratio. (c) A shell theory based residual stress estimation scheme has been developed to interrelate all parametric analysis results for circumferential girth welds, which can also be used to estimate residual stress distributions in both through-thickness and at any distance away from the weld, for cases that are not covered in the parametric study. (d) In a similar manner, a curve bar theory based residual stress estimation scheme has also been developed for longitudinal seam welds. These developments can significantly advance the residual stress profile prescription methods stipulated in the current national and international FFS Codes and Standards such as 2007 API 579 RP/ASME FFS-1 and BS 7910: 2011.

<div>The numerical calculation of the electromagnetic fields within electric machines is sensitive to the magnetic characteristic of steel. However, the magnetic characteristic of steel is uncertain due to fluctuations in alloy composition, possible contamination, and other manufacturing process variations including punching. Previous attempts to quantify magnetic uncertainty due to punching are based on parametric analytical models of <i>B-H</i> curves, where the uncertainty is reflected by model parameters. In this work, we set forth a data-driven approach for quantifying the uncertainty due to punching in <i>B-H</i> curves. In addition to the magnetic characteristics of steel lamination, the remanent flux density (<i>B_r</i>) exhibited by the permanent magnets in a permanent magnet synchronous machine (PMSM) is also uncertain due to unpredictable variations in the manufacturing process. Previous studies consider the impact of uncertainties in <i>B-H</i> curves and <i>B_r</i> of the permanent magnets on the average torque, cogging torque, torque ripple and losses of a PMSM. However, studies pertaining to the impact of these uncertainties on the combined machine/drive system of a PMSM is scarce in the literature. Hence, the objective of this work is to study the effect of <i>B-H</i> and <i>B_r</i> uncertainties on the performance of a PMSM machine/drive system using a validated finite element simulator. </div><div>Our approach is as follows. First, we use principal component analysis to build a reduced-order stochastic model of <i>B-H</i> curves from a synthetic dataset containing <i>B-H</i> curves affected by punching. Second, we model the the uncertainty in <i>B_r</i> and other uncertainties in <i>B-H</i> characteristics e.g., due to unknown state of the material composition and unavailability of accurate data in deep saturation region. Third, to overcome the computational limitations of the finite element simulator, we replace it with surrogate models based on Gaussian process regression. Fourth, we perform propagation studies to assess the effect of <i>B-H</i> and <i>B_r</i> uncertainties on the average torque, torque ripple and the PMSM machine/drive system using the constructed surrogate models.</div>

In this study, dynamic crack propagation in brittle materials has been studied using a regularized phase field approach.The phase field model used has been validated using specific experimental results of a dynamic in-plane fracture. The crack branching phenomena and existence of a limiting crack tip velocity has been validated using a mode I simulation set-up. A parametric study has also been performed so as to normalize the various numerical parameters that affect the velocity at the crack tip. Following the validation of the phase field model a stochastic analysis of a PBX microstructure has been performed. The microstructure has a high HMX volume fraction of 79\%. The energetic material is HMX and the binder used is Sylgard. Artificial defects are introduced in the system using phase field cracks. The analysis uses a finite element framework that accounts for various thermal-mechanical processes like deformation, heat generation, conduction, fracture and frictional heating at the crack surfaces. The effect on the temperature and damage field due to varying parameters like loading velocities and critical energy release rates is studied. Critical hotspot formation due to localized frictional heating is also studied. A concept of dirty binder is introduced to increase the grain volume fraction of the energetic in the composite. This amounts to a homogenized binder that accounts for the influence of the subsume particles that do not contribute to fracture but affect material properties of the binder.

In the current framework of Evolutionary Biology, Paleontology has an important role to play. The fossil record represents a fundamental aspect in studies on the evolution of morphology, since from its study it is possible to retrieve reliable data on many pertinent aspects, e.g., rates of evolution, the role of mass extinctions on species diversity, the polarity of character changes, and a glimpse into morphotypes that dont exist nowadays. At the same time, new tools and methods, such as computed tomography, digital reconstructions, and Finite-Element Analysis, known collectively as digital or virtual paleontology, have brought novel possibilities on how to formulate and answer paleontological questions. In this Thesis, I employ digital paleontological techniques to analyze the patterns of morphological evolution of the skull of turtles and, based on these data, I provided novel interpretations of the neuroanatomical and functional relations of specific cranial traits to the whole skull architecture. Organized in four chapters, an overview of the osteological, muscular, developmental, and functional evolution of the craniocervical system of turtles is provided. By applying computed tomography and other 3-D digital methods, I performed reconstructions of the jaw adductor musculature and the neuroanatomical structures of one of the earliest turtles, Proganochelys quenstedti, to investigate the early evolution of the adductor chamber and the sensorial anatomy in this taxon. A new extinct side-necked turtle species, Yuraramirim montealtensis, is described, and its brain, inner ear, and neurovascular system were reconstructed in order to provide an account of the paleoneuroanatomy in one of the major turtle groups, the pleurodires. For the last chapter, I performed Finite-Element Analyses based on 3-D digital models of a series of extinct and extant taxa, together with hypothetical simulated morphotypes, to analyze the relation between muscle stress distribution patterns and skull architecture in the group. A scenario of progressive correlation between neck and skull morphological modifications is presented, which may be related to the great diversification of turtles during the Jurassic / No estado atual da Biologia Evolutiva, a Paleontologia possui um importante papel. O registro fossilífero representa um aspecto fundamenteal em estudos da evolução da morfologia, uma vez que, por meio de seu estudo, é possível recuperar dados confiáveis acerca de muitos importantes aspectos, e.g., taxas de evolução, o papel das extinções em massa na diversidade de espécies, a polaridade de mudanças de caracteres e um vislumbre de morfótipos que não mais existem atualmente. Ao mesmo tempo, novas ferramentas e métodos, como tomografia computadorizada, reconstruções digitais e análises de elementos finitos, conhecidos coletivamente como paleontologia digital ou virtual, trouxeram novas possibilidades acerca de como formular e responder perguntas paleontológicas. Nesta Tese, eu utilizo técnicas da paleontologia digital para analizar os padrões de evolução morfológica do crânio das tartarugas e, com base nestes dados, forneço novas interpretações sobre as relações neuroanatômicas e funcionais de características cranianas específicas para com a arquitetura craniana como um todo. Organizada em quatro capítulos, uma visão geral sobre a evolução osteológica, muscular, ontogenética e funcional do sistema craniocervical das tartarugas é apresentada. Aplicando tomografia computadorizada e outros métodos digitais 3-D, realizei reconstruções da musculature adutora da mandíbula e de estruturas neuroanatômicas de uma das mais antigas tartarugas, Proganochelys quenstedti, para investigar a evolução inicial da câmara adutora e anatomia sensorial neste táxon. Uma nova espécie de tartaruga pleurodira, Yuraramirim montealtensis, é descrita, e seu cérebro, ouvido interno e sistema neurovascular foram reconstruídos fornecendo informações sobre a paleoneuroanatomia em um dos principais grupos de tartarugas, Pleurodira. No último capítulo, foram conduzidas análises de elementos finitos baseadas em modelos digitais 3-D de uma série de táxons extintos e viventes, além de morfótipos hipotéticos simulados, para analizar a relação entre padrões de distribuição de estresse gerados por contração muscular e arquitetura craniana no grupo. Um cenário de correlação progressiva entre modificações morfológicas no pescoço e no crânio é apresentado, que pode estar relacionado à grande diversificação das tartarugas durante o Jurássico