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Threaded connectors have been used in a variety of engineering structures for hundreds of years. Although stress analysis of threaded connectors has been performed since the early 1900's, there are still areas that are not fully understood. The way in which eccentricity affects the fatigue performance and stress distribution is one such area, and is the main area of research described in this thesis. The techniques of photoelasticity and fatigue testing were used to determine the effect of eccentricity on the stresses and fatigue performance of bolts. The results show that eccentric loading has a significant effect on the fatigue performance, but that this effect can be quantified if the local stress amplitude is considered. The photoelastic analysis results show the eccentricity slightly increases the stress intensity factors at the crack tip. A number of two-dimensional and three-dimensional finite element models were created to detennine the salient characteristics of the models. The models were validated against the resuh from the photoelastic analysis and the results agreed well. Accurate results can be obtained from a two-dimensional model, but the information obtained is limited unless many models are created. However, if a three-dimensional model is created more information can be obtained, but the nut thread run-out must be accurately modelled to obtain the correct stress distribution. The shape of cracks occurring in cyclically loaded steel bolts and the effect of crack shape on the stress distribution was also investigated. The photoelastic analysis of cracked bolts failed to predict the shapes of cracks occurring in cyclically loaded bolts. It is suggested that the inability of photoelasticity to model plasticity is the cause of this failure and this is supported by results from an elastic-plastic finite element model.

A thesis submitted to the Faculty of Science University of the Witwatersrand Johannesburg In fulfilment of the requirements for the Degree of Doctor of Philosophy June 2015 / The first two chapters of this thesis deals with the synthesis of 6H-benzo[d]-naphtho[ 1,2- b]pyran-6-one motif found in gilvocarcin as well as related aromatic compounds containing the aromatic pyranone moiety. The synthesis was undertaken by employing the Suzuki- Miyaura cross coupling reaction and a novel N-bromosuccinimide induced ring cyclization reaction to afford the pyranone. It was established that the treatment of both [2-(1,4- dimethoxynaphthalen-2-yl)phenyl]methanol and (2',5'-dimethoxy-[1,1'-biphenyl]-2- yl)methanol separately with N-bromosuccinimide results in the unexpected synthesis of a naphthopyranone ring system in the form of 12-methoxy-6H-dibenzo[c,h]chromen-6-one and 2-methoxy-6H-benzo[c]chromen-6-one respectively. Application of the same methodology for the attempted synthesis of related compounds namely, 1-hydroxy-12-methoxy-6Hdibenzo[ c,h]chromen-6-one and 8-fluoro-12-methoxy-6H-dibenzo[c,h]chromen-6-one unfortunately did not generate the desired results. Attempts were made to elucidate the mechanism of this reaction. The most apparent mechanism indicates that Nbromosuccinimide, in the presence of air, oxidizes the benzylic alcohol to an aldehyde which is then converted to an acid bromide allowing for the ring closure with the adjacent aromatic ether to afford the desired pyranone. In Chapter 3 and 4 of this thesis we dealt with the synthesis of benzo[b]phenanthridine-7,12- dione motif, the backbone of biologically important secondary metabolite jadomycin B. Again, a key step involves employing the Suzuki-Miyaura cross coupling reaction. The synthetic methodology also sheds some light on the dynamics of the ring closure of benzylic amines onto naphthoquinones resulting in the synthesis of benzo[i]phenanthridine-11,12- dione, 12-methoxybenzo[i]phenanthridine and 1-hydroxybenzo[i]phenanthridine-11,12-dione. The synthesis of benzo fused phenanthridines has been undertaken in Chapter 5 and 6 by employing Suzuki-Miyaura cross coupling reaction and a potassium t-butoxide and light mediated cyclization reaction as the key steps. The synthesis of 5- phenylbenzo[i]phenanthridine was undertaken successfully but attempts to execute the same methodology to form a compound library of related benzo-fused phenanthridines was unsuccessful. The same methodology employing a Suzuki-Miyura cross coupling reaction and potassium tbutoxide and light mediated cyclization reaction was applied in Chapter 7 and 8 of the thesis directed towards the synthesis of 13H-indolo[3,2-c]acridine and 3-methoxy-13H-indolo[3,2- c]acridine. The successful synthesis of the 13H-indolo[3,2-c]acridine is reported using this methodology.

Orientador: Osvaldo Luís Manzoli / Coorientador: Luís Antônio Guimarães Bitencourt Júnior / Banca: Caio Gorla Nogueira / Banca: Leonardo José do Nascimento Guimarães / Resumo: Este trabalho aborda a simulação de problemas que envolvem contato mecânico, utilizando uma nova técnica de acoplamento de malhas independentes de elementos finitos. Esta técnica se baseia no uso de elementos finitos especiais denominados elementos finitos de acoplamento, que compartilham nós de malhas independentes. A técnica é capaz de estabelecer a interação entre duas malhas de elementos finitos, representando dois domínios diferentes, que compartilham entre si uma ou mais de suas faces. No caso mais geral, devido a possíveis diferenças nas dimensões e naturezas dos domínios, as posições dos nós na face de uma malha podem não coincidir com as posições dos nós da outra malha. As principais vantagens da técnica proposta são: (i) não há adição de graus de liberdade para a resolução do problema; (ii) um acoplamento não rígido pode ser considerado para descrever o comportamento não linear de interfaces similares aos modelos coesivos e (iii) malhas não compatibilizadas de quaisquer dimensões e quaisquer tipos de elementos finitos podem ser compatibilizadas. Como extensão da utilização da técnica, visa-se representar a interação entre duas peças genéricas distintas, demonstrando a capacidade da técnica em simular efeitos de contato, ou de perda de contato, de forma coerente e precisa. Foram empregados modelos baseados na mecânica do dano contínuo para simular efeitos de atrito em uma formulação de acoplamento não rígido. Os resultados obtidos neste trabalho demostram que a repre... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work deals with the numerical simulation of contact problems using a novel technique for coupling non-matching finite element meshes. The technique is based on the use of special finite element termed coupling finite element, which share nodes with non-matching meshes. Thus, the interaction among two non-matching meshes, representing two different subdomains of a problem can be described. In additional, this technique has demonstrated to be highly versatile, since no additional degree of freedom is introduced to the problem; non-rigid coupling can be considered to describe the nonlinear behavior among the subdomains and nonmatching meshes of any dimension and any type of finite elements can be coupled. In this work the technique is applied to simulate the interaction among some parts of mechanical components discretized initially in finite elements in a totally independent way, by demonstrating its capability to represent contact problems or loss of adherence. A combined constitutive model based on the damage mechanics theory is used for modeling the friction effects using a non-rigid coupling procedure. The results demonstrated that the strategy applied can represent the interaction among the parts of mechanical components, coherently and accurately / Mestre

The use of dough moulding compound (DMC) as a structura~ material will be feasible as more information on mechanlcal properties becomes available. In this investigation, room temperature tensile and fatigue properties were determined prior to the testing and evaluation of simple joints in DMC. The DMC was supplied in the form of compression moulded sheets. Tensile tests were conducted to British Standards specification to obtain the mechanical properties and to identify possible sources of variability in properties. Differences in tensile strength due to sheet-to-sheet variability and specimen orientation within a sheet were significant but there was no significant variation due to the cross-head speed over the range O.05mm/min to 300mm/min. Tensile fatigue tests were conducted to British Standards specification. The scatter of fatigue lives was found to be greater than that for other reinforced plastics, but was adequately described by both the Log-Normal and Weibull distributions. In tensile and fatigue tests on larger specimens there was no size effect on tensile strength, but the fatigue strength at a given life and probability of failure was reduced ,slightly. When specimens contained bolt holes, the tensile strength decreased marginally, but the fatigue strength was not affected. Transverse compressive stresses due to a bolt load had little effect on the fatigue behaviour and changes in the cyclic-or static stress did not significantly alter the bolt load relaxation. Cyclic stress was found to cause greater bolt load relaxation than the corresponding mean stress. In tensile and fatigue tests on single shear lap joints, benditig wa~ the main cause of failure and the joint efficiency was low, 43% in tension and 51% in fatigue. By loading the specimens through the bolts at one end, bending was eliminated and the joint efficiency increased to 62% in tension and to 78% in fatigue

An apodized grating coupler with the best coupling efficiency hitherto reported for shallow-etched waveguide grating couplers is described. By appropriate choice of waveguide/grating thicknesses and varying the coupling strength of the grating coupler via tailoring its fill factor to optimize the mode matching, a coupling loss of only 1.2dB was obtained for each fiber/silicon waveguide interface with a slightly titled optical fiber. / Photonic integrated circuits (PICs) based on Silicon-on-insulator (SOI) substrate were proposed to make miniaturized photonic devices on chip, so that low-cost and compact devices for applications including sensing, inter/intra-chip communications and optical fiber communications could be made. One of the key challenges in the development of highly integrated PICs is efficient coupling of light between a submicron-sized nanophotonic wire and an optical fiber due to the large loss inherent from the mismatch in mode field size between the optical fibers and the nanophotonic wire waveguides. An attractive approach for efficient coupling is to use diffractive grating couplers which show many advantages over alternative approaches. However the angled alignment of the optical fiber to the grating as reported in the previous work is not desirable for a low-cost optical packaging process. / The 2D grating couplers could be used as polarization splitter. Polarization insensitive coupling and polarization-diversity circuits are realized by the 2D grating couplers. We also demonstrated a novel silicon waveguide grating which serves dual functions: as a 1x2 variable integrated beam splitter/combiner and as an out-of plane diffractive element for coupling light. The split ratio can be tuned by changing the launch position of the optical fiber without introducing much excess loss. An integrated Mach-Zehnder interferometer (MZI) is implemented with this novel functional element. This MZI was demonstrated as a demodulator for differential phase-shift-keying (DPSK) signal. / We demonstrated a simple technique to realize vertical fiber coupling with linearly chirped grating periods. No additional fabrication process is required yet a comparable coupling efficiency is achieved with the proposed chirped grating couplers with vertical optical fibers. Design and experimental results of onedimensional (lD) gratings, two-dimensional (2D) gratings, focusing gratings and fully-etched nanoholes gratings are described in the thesis. We also describe the waveguides and grating couplers fabricated on silicon-on-sapphire for mid-infrared applications. / Chen, Xia. / Adviser: H.K. Tsang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Curvic couplings have been widely applied in industry and almost can be seen in the index table. Following the development of the precision machine industry, except the manufacturing precision, the positioning accuracy is also concerned to meet the demands for curvic couplings. The aim of this thesis is to investigate on manufacturing errors and positioning accuracy of curvic couplings. Discuss the geometric and indexing characteristics of curvic couplings firstly. In the meantime, the new parameter tooth surface of curvic couplings is derived by tooth generating theory. Than, mathematical models are established to simulate curvic couplings at present that are manufactured by grinding machine with different setting errors. Secondly, the practical examples based on the effects of elemental error on the manufacturing error are investigated. Finally, an experimental apparatus is built to measure the actual positioning accuracy of curvic couplings at different input speeds.

This study examines the effects of various rib properties and reinforced section geometries on the splitting force distribution around tensile lapped splices. The study makes use of a test specimen which idealizes the situation that exists in a tensile lapped splice between adjacent lateral cracks. The test specimen always failed by a longitudinal splitting of the concrete cover along a predefined failure plane. During the study the Influence of relative rib area, rib profile, amount of secondary link reinforcement, lateral pressure and bar spacing within the lap on the ultimate bond strength of the lap were examined. It was found that, for hot rolled (untwisted) deformed bars with crescent shaped ribs the orientation of the ribs to the splitting plane significantly affected the ultimate bond strength of the test specimen and, whilst the relative rib area was a good measure of a deformed bars performance In bond, it could not distinguish between the different orientations used. Further, since the maximum percentage Increase In ultimate bond stress for the same bar between orientations was of a similar magnitude to that observed for a doubling of a bars relative rib area the author recommends that bar orientation be taken into account when detailing tensile lapped splices. The presence of link steel perpendicular to the splitting plane did not significantly influence the ultimate bond strength of the model test specimen although the presence of lateral pressure did. The stress in the links at the occurrence of a full length splitting crack was less than 100 N/mm2. The finite element method was used to examine the two fundamental hypotheses describing the bond action of deformed reinforcing bars and to examine the implications of the assumption that the splitting forces around the circumference of a reinforcing bar are distributed proportionally to the rib height. The finite element analysis was also used to study the effect of varying the distance between the lapped bars on the spitting force distribution around the lapped bars. The results of a linear elastic analysis showed that both rib profile and bar spacing had a significant effect on the distribution of splitting forces around a tension lapped splice

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