Robust fault analysis (FA) including the diagnosis of faults and predicting their level of severity is necessary to optimise maintenance and improve reliability of Aircraft. Early diagnosis of faults that might occur in the supervised process renders it possible to perform important preventative actions. The proposed diagnostic models were validated in two experimental tests. The first test concerned a single localised and generalised roller element bearing fault in a permanent magnet brushless DC (PMBLDC) motor. Rolling element bearing defect is one of the main reasons for breakdown in electrical machines. Vibration and current are analysed under stationary and non-stationary load and speed conditions, for a variety of bearing fault severities, and for both local and global bearing faults. The second test examined the case of an unbalance rotor due to blade faults in a thruster, motor based on a permanent magnet brushed DC (PMBDC) motor. A variety of blade fault conditions were investigated, over a wide range of rotation speeds. The test used both discrete wavelet transform (DWT) to extract the useful features, and then feature reduction techniques to avoid redundant features. This reduces computation requirements and the time taken for classification by the application of an orthogonal fuzzy neighbourhood discriminant analysis (OFNDA) approach. The real time monitoring of motor operating conditions is an advanced technique that presents the real performance of the motor, so that the dynamic recurrent neural network (DRNN) proposed predicts the conditions of components and classifies the different faults under different operating conditions. The results obtained from real time simulation demonstrate the effectiveness and reliability of the proposed methodology in accurately classifying faults and predicting levels of fault severity.

Maintenance cost is one of the important issues in railway heavy-haul operations. In most of the cases, these costs are majorly referring to reprofiling and changing the wheels of the locomotives and the wagons. The main reason of the wheel damages is usually severe wear and/or surface initiated rolling contact fatigue (RCF).This work tries to enhance and improve the knowledge of the wheel wear and RCF prediction models using dynamic simulations. While most of the contents of this study can be generalised to other operational networks, this study is focused on the locomotives and wagons of the Swedish iron-ore company LKAB. The trains are operating on the approximately 500 km long IORE line from Luleå to Narvik in the north of Sweden and Norway respectively.Firstly, a literature survey of dynamic modelling of the wagons with various three-piece bogie types is presented. Then, with concentrating on the standard three-piece bogies, parameter studies are carried out to find out what the most important reasons of wheel damages are. Moreover, the long-term stability of wheel profiles of the IORE wagons is analysed. This is done by visualising the wear and RCF evolution on the wheel profiles over 150,000km of simulated running distance.Most of the calculations for the wagons are repeated for the locomotives. However, traction and braking are also considered in the simulation model and their effects on wheel damages are briefly studied. To improve the accuracy of the wheel damage analysis, a newly developed algorithm called FaStrip is used to solve the tangential contact problem instead of FASTSIM. The damage prediction model developed in the thesis is used to study the effects of increasing axle load, correcting the track gauge, limiting the electro-dynamic braking and using a harder wheel material on the wheel life. Furthermore, a new method is developed to predict the running distance between two consecutive reprofilings due to severe surface initiated fatigue. The method is based on shakedown analysis and laboratory tests.Most of the research works in wear calculation are limited to two approaches known as wear number and Archard methods. The correlation between these two methods is studied. The possibility of using the relation between the two methods for the wear calculation process is investigated mainly to reduce the calculation time for wheel profile optimisation models. / <p>QC 20171219</p>

The aim of the work presented in this thesis is to clarify one of the most fundamental aspects of fatigue damage in bearings steels through critical experiments, in particular whether damage in the form of cracks precedes hard “white-etching matter" formation, which is carbon supersaturated nanoscaled ferrite. Heat treatments have been designed to create four different crack types and distributions: scarce martensite plate cracks, fine grain boundary cracks, abundant martensite plate cracks, and surface cracks. Subsequent rolling contact fatigue experiments showed that the amount of hard white-etching matter is higher in pre-cracked samples compared to those without prior damage and that its formation mechanism is the frictional contact of disconnected surfaces within the bulk that elevate the temperature and localise deformation. These key experiments indicate that hard white-etching matter is the consequence, not the cause, of damage. Therefore, one way to avoid white-etching matter is by increasing the toughness of the material. The macroscopically homogenous distribution of microcracks proved also to be a useful rolling contact fatigue life enhancer due to damage deflection via crack branching and a powerful trap for diffusible hydrogen. Successful trapping was corroborated by the inability of hydrogen to cause crack propagation via embrittlement or accelerate white-etching matter generation during rolling contact fatigue. By also studying the behaviour of a nanostructured bainitic steel under rolling contact fatigue, it was found that its degradation mechanism is ductile void formation at bainitic ferrite/stress-induced martensite interfaces, followed by growth and coalescence into larger voids that lead to fracture along the direction of the softer phase as opposed to the conventional damage mechanism in 52100 steel of crack initiation at inclusions and propagation. Given the relevance of phase quantification in nanobainite and the possible surface artefacts introduced by preparation, alternative methods to X-ray diffraction such as magnetic measurements were also investigated. The lack of hard white-etching matter obtained in the carbide-free nanostructured bainite led to conclude that an alternative route to mitigate hard white-etching matter could be by eliminating pre-eutectoid carbides from the microstructure, therefore restricting their dissolution and ultimate carbon supersaturation of the mechanically deformed and homogenised nanoferrite.

Bearings are employed in a number of applications under extremely demanding conditions. During long operation times, the material undergoes rolling contact fatigue where microstructural damage manifests as dark-etching regions and white-etching areas, which display different properties from the surrounding region. The aim of this study is to identify the mechanisms for such damage and to suggest models that can explain the influence of the initial microstructure and test conditions. In order to appraise the stress state in rolling contacts, two testing techniques were employed and it was examined if the testing methods could reproduce the same damage as in bearing operation. During ball-on-rod fatigue testing, microcracks were generated adjacent to inclusions and some were decorated with white-etching areas. Repetitive push tests showed a similar extent of subsurface hardening compared to the ball-on-rod tests, and allowed the strain per stress cycle to be measured. The microstructural alterations in a white-etching area were studied both on a macroscale and on an atomic-scale. The degree of stress concentration near a microcrack was calculated employing a nite element method. The microstructure, as well as the segregation behaviour of alloying elements in the white-etching area, were investigated by employing transmission electron microscopy and atom probe tomography. A nanocrystalline structure with scattered carbide particles was observed in the white-etching area. Carbon and silicon segregation was highly pronounced in some boundaries of dislocation cell structures. Models were suggested to account for the microstructural alterations during rolling contact fatigue. Carbide coarsening in dark-etching regions was modelled by considering how carbon di usion is assisted by dislocation glide. The predicted hardness evolution was consistent with experimental observation. The kinetics of carbide dissolution in white-etching areas was calculated by taking two processes into account: deformation accumulation and carbon diffusion. These models suggest that the microstructural changes during bearing operation can be controlled by tailoring the initial microstructure and managing the test conditions.

The aim of this finish work is an analysis of selected demographic time series and calculation of their predictions. Concretely, it deals with time series of annual crude birth rate, crude death rate, and the average age of mothers at first birth, all for the time period of 1960-2013. First, demographic terms used further in the work are defined. There is also a theoretical part describing the statistical methods used, specifically the methodology of time series from authors Box-Jenkins. Developement of each time serie is evaluated socio-demographically and the procedure of selecting the most appropriate interpolation model and calculation of predictions derived from it are described. There is also description of a process of selecting a suitable model based on the extrapolation method of predictions with Rolling Origin, construction of predictions derived from it and their comparison with the most suitable interpolation model. At the end there is a comparison of the time series of crude birth rate between the Czech Republic and selected developed country (Sweden), which brings interesting results.

The microstructures of the near-surface layers on AA3104 aluminium alloys and their evolution through rolling and deep drawing processes have been investigated. The effect of the near-surface layers on the optical property of AA3104 aluminium alloy has also been assessed. It was revealed that two types of near-surface deformed layers, both with different microstructures different from the underlying bulk alloy, were generated on the surface of AA3104 aluminium alloy during rolling. Both of them are characterized by ultrafine, equiaxed grains, with diameters <100 nm for type A near-surface deformed layer and <200 nm for type B near-surface deformed layer. A high population density of nano-sized, oxygen-rich particles is present along grain boundaries within type A deformed layer. But type B deformed layer is free of oxygen-rich particles. Type A deformed layer was generated through two mechanisms, i.e. geometric dynamic recrystallization and mechanical alloying. Rolling introduced plastic strain in the surface/near-surface region of aluminium sheet was of sufficient magnitude to cause geometric dynamic recrystallization and thus microstructure refinement. In addition, the incorporation of oxides into the near-surface region was also involved in the formation of type A deformed layer. However, the formation of type B deformed layer was only attributed to severe strain induced geometric dynamic recrystallization. Type A deformed layer was mainly formed at the early stages of hot rolling. The subsequent rolling and deep drawing reduced the thickness of type A deformed layer by distributing it over a larger surface area. During cold rolling, type A deformed layer broke into patches with the extension of alloy surface. Type B deformed layer may be generated on the nascent surface if the strain is sufficiently severe to cause geometric dynamic recrystallization. For the hot rolled alloy sheets, the surface/near-surface region is mainly covered by type A deformed layer. However, for the alloys after cold rolling, only limited area is covered with type A deformed layer. The thicknesses of the near-surface deformed layers are not uniform across the surface of AA3104 aluminium alloy. The maximum thickness of type A deformed layer on transfer slab is approximately 4 µm, while that on re-roll gauge sheet is ~1 µm, and ~0.8 µm on the final gauge sheet, ~400 nm on formed cup and ~100 nm on formed can. Type A deformed layer is randomly distributed as patches on the cold rolled aluminium sheet. The reflectivity of oxygen-rich particles is lower compared with the reflectivity of aluminium. As a result, the type A deformed layer patches absorb more incident light than the area without type A deformed layer. Further, there are plenty of micro-scale mini-cracks present on type A deformed layer, their opening sizes are in the equivalent scale of the wavelength of visible light. The incident light may not able to be reflected out if they go into these mini-cracks. It is more prone to happen for short wavelength light since it is easier for them to go into the mini-cracks than long wavelength light. As a result, less short wavelength visible light is reflected from the type A deformed layer patches. Thus, such patches exhibit a yellow appearance while the surrounding area appears the original silver white aluminium appearance. The aluminium sheet with a high coverage of type A deformed layer exhibits a low total reflectance. Further, its total reflectance is with a significant “red shift”. Neither the macro-scale surface roughness nor the ultrafine grain size affects the total reflectance of aluminium alloys. The total reflectance of aluminium alloys is primarily dependent on the presence of type A deformed layer.

Les conditions de fonctionnement rencontrées dans la problématique de nouvelles générations d'alternateurs automobiles avec des chargements variables et un environnement mécanique complexe déformable ont un effet non négligeable sur le comportement mécanique du roulement et par conséquent sur sa durée de vie. Il est proposé dans ce travail une approche permettant de prendre en compte ces paramètres dans l'estimation de la durée de vie des roulements. La répartition des efforts obtenue des considérations statiques sont utilisés dans un modèle dynamique simplifié permettant de déterminer de l'état de contrainte au cours du temps dû au passage de billes sur la piste de roulement. L'approche multi-échelle de Dang Van couplée à une loi de cumul d'endommagement a permis de déterminer le nombre de cycles avant l'apparition des premiers signes de fatigue. La dernière phase du travail concerne l'aspect expérimental qui a montré que le phénomène de fatigue n'est pas la seule cause de dégradation des roulements montés dans les alternateurs automobiles. / The operating conditions encountered in the new generations of automotive alternators with variable loads and a deformable complex mechanical environment have a significant effect on the mechanical behavior of the bearing and hence its fatigue lifetime. An approach that takes into account these parameters in the ball bearing fatigue lifetime has been proposed in this work. The load distribution obtained from static considerations are used in a simplified dynamic model in order to determine the time-dependent stress state due to ball rolling on the raceway. The Dang Van multiscale approach coupled with a damage law was applied to determine the number of cycles before the apparition of the first signs of fatigue. The last phase of work involves the experimental aspect that shows that the fatigue phenomenon is not the only cause of degradation of bearings mounted in automotive alternators.

The purpose of this study was to determine whether working in the field of deaf education, as opposed to general education, results in a higher level of technology integration. A secondary goal was to determine if deaf educators who are deaf integrate technology at a higher level than their hearing counterparts. The instrument chosen for this study was the LoTi Technology Use Profile, a tool used to explore the role of technology in the classroom. A total of 92 participates were included in the study of which 48 were regular educators and 44 were deaf educators. The participants were selected from a population pool whereby teachers were presumably pre-disposed to using technology based upon their attendance at a technology training session in the form of a conference or a class. Deaf educators as a whole did not perform as well as general educators on the LoTi scales. Given the fact that the technology-minded general educators who comprised the sample population of this study scored exceptionally high on the LoTi scales, further research is needed to ensure comparability between the two groups. The findings of the current study do suggest, though, that deaf educators who are deaf have the potential to integrate technology to a greater degree than deaf educators who are hearing. Thus, a primary recommendation is to conduct a national LoTi survey of typical, rather than technology-minded, deaf educators as a comparison to the 2004 national survey of typical general educators.

Orientador: José Maria Campos Dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-27T18:02:49Z (GMT). No. of bitstreams: 1 Gali_MarcosRodolfo_M.pdf: 8846565 bytes, checksum: b82ad0724e54e69642945eea2e744eaf (MD5) Previous issue date: 2015 / Resumo: Em 2012, Rhyne & Cron desenvolveram um modelo analítico para estimar a mínima Resistência ao Rolamento (RR) para pneus destinados aos veículos de passageiro. Os parâmetros estudados pelos autores foram a área de contato, a espessura e a largura da rodagem, o raio da cintura metálica, o módulo elástico do composto da banda de rodagem, a carga vertical imposta, a pressão de inflação do pneu e a área efetiva de contato do pneu com o solo. Para o fator área de contato, os autores simplificaram a abordagem matemática que defini a interação entre o pneu e o pavimento, não considerando a área total formada devido à deformação na região de interação com o pavimento (que muda com a pressão interna do pneu e com a carga imposta sobre o mesmo). O objetivo do presente estudo foi desenvolver um modelo analítico baseado no modelo de Rhyne & Cron, para estimar a resistência ao rolamento de pneus de carga, considerando a área de contato formada na região de interação entre o pneu e o pavimento. Os modelos analíticos foram implementados em MatLab versão R2008a para obtenção das curvas de resistência ao rolamento e compará-las com as curvas obtidas através de modelo numérico que interagiu com um modelo de elementos finitos (FEM). Os resultados dos modelos analíticos e numéricos foram validados e comparados com resultados experimentais obtidos em laboratório segundo condições da norma ISO 28.580. Os resultados obtidos através do modelo analítico proposto mostraram uma satisfatória correlação comportamental quando comparados com as curvas experimentais, sendo uma ferramenta interessante durante o desenvolvimento do projeto do pneu, pois permite ter uma estimativa da resistência ao rolamento / Abstract: In 2012, Rhyne & Cron developed an analytical model to estimate the minimum Rolling Resistance (RR) for tires intended for passenger vehicles. The parameters studied by the authors were the contact area, the thickness and width of the tread, the radius of the metal belt, elastic modulus of the tread compound, the imposed vertical load, the tire inflation pressure and effective contact area tire with ground. For contact area's factor, the authors simplified the mathematical approach that define the interaction between the tire and the ground, not considering the total area formed due to deformation in the interaction region with the ground (which changes with the tire internal pressure and the imposed load). The objective of this study was to develop an analytical model based on the Rhyne & Cron model to estimate the truck tires' rolling resistance, considering the contact area formed at the interaction region between the tire and the pavement. The analytical models were implemented in MatLab R2008a version to obtain the rolling resistance curves and compare them with the curves obtained through numerical model that interacted with a finite element model (FEM). The results of analytical and numerical models were validated by comparison with experimental results obtained according ISO 28580 standard. The obtained results using the proposed analytical model showed a satisfactory behavioral correlation when compared with the experimental curves, being an interesting tool for the development of tire design because it allows having an estimation of the rolling resistance / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

O processo de roleteamento é um tratamento superficial, comumente utilizado em peças fabricadas em aços e ferros fundidos nodulares, em regiões onde há concentradores de tensões, com o intuito de melhorar as propriedades de resistência à fadiga. Este processo endurece e introduz tensões residuais compressivas na camada superficial do material, através de deformação controlada, provocando uma redução das tensões de tração que atuam na superfície da peça submetida a carregamentos cíclicos. Este trabalho teve como principal objetivo o estudo do efeito do roleteamento superficial sobre o comportamento em fadiga de um ferro fundido nodular de matriz perlítica, utilizado na fabricação de virabrequins pela indústria automobilística. Foram realizados ensaios de fadiga por flexão rotativa em corpos de prova lisos e com entalhe. Os corpos de prova com entalhe foram divididos em dois grupos, com e sem roleteamento superficial. Foi utilizado entalhe com geometria semicircular com raio de 1,20mm e profundidade de 0,70mm. Para o processo de roleteamento foi utilizado um rolete com diâmetro de 15,00mm e com raio de curvatura de 1,30mm e aplicada uma força de compressão de 2390N. A introdução de tensões residuais compressivas pelo trabalho a frio, dificultou a nucleação e a propagação de trincas na camada superficial dos entalhes roleteados. Isto ficou evidenciado pelo aumento do valor do limite de fadiga para 483MPa obtido para o material entalhado e roleteado, enquanto que para o material nas condições de sem entalhe e somente entalhado estes valores foram de 300MPa e 168Mpa, respectivamente. / Surface rolling is a mechanical treatment commonly used in parts fabricated with steel and ductile cast iron, specifically in stress concentration regions, to improve fatigue properties. This process hardens and introduces compressive residual stresses to the surface of the material through the application of controlled strains, thus provoking a reduction of resulting tensile stress at its surface under cyclic loading. This work deals with the effect of surface rolling on high cycle fatigue behavior of a pearlitic ductile cast iron used in crankshaft by automotive industries. Rotating bending fatigue tests were performed in both smooth and notched specimens. The notched specimens were divided into two groups: with and without surface rolling treatment. The specimens notch geometry was semicircular with radius of 1.20mm and depth of 0.70mm. The rolling treatment was carried out using a roller with diameter of 15,00mm, curvature radius of 1.30mm and a compression force of 2390N. The introduction of compressive residual stresses under cold work made difficult the nucleation and propagation of the crack on the rolled surface of the notch. It was confirmed by the increase of the endurance limit of the surface rolled specimens to 483MPa in comparison with the smooth and notched specimens, respectively, 300MPa and 168 MPa.