Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-15Bitstream added on 2014-06-13T19:14:24Z : No. of bitstreams: 1 alves_prg_me_guara.pdf: 1144534 bytes, checksum: c564c6fdb34127fdaaba0cd2ec9f184d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta estudos de usinabilidade de peças de madeira de eucalipto, tendo por objetivo principal efetuar análises da resistência de juntas coladas em relação à qualidade das superfícies usinadas, a fim de se verificar a influência da rugosidade superficial sobre a adesão das superfícies coladas com adesivo à base de acetato de polivinila (PVA). Amostras da espécie de madeira Eucalyptus saligna foram preparadas para testes de resistência na lâmina de cola em ensaios de ruptura por cisalhamento e por tração normal segundo a norma NBR 7190. As superfícies de colagem foram preparadas por operação de fresamento empregando-se velocidade nominal de avanço de 11,0 m/min e posteriormente por operação de lixamento empregando-se cinco diferentes granulometrias de lixas, de granas: 80, 100, 120, 150 e 220. Depois de lixadas, as superfícies foram submetidas à medição da rugosidade com rugosímetro equipado com uma ponta apalpadora de diamante, de forma cone-esférica, com raio de ponta de 2µm, em conjunto com o programa de análise de superfícies. Dos resultados obtidos podem-se destacar os melhores desempenhos de resistência a ruptura; ao cisalhamento para superfícies lixadas por lixa de grana 220; à tração normal para superfícies lixadas por lixa de grana 120 / This paper shows studies on machinability of eucalyptus wood battens; main goal is make analysis of resistance bonded joints in relation the quality of machined surface to determine the influence of surface roughness on the adhesion of the bonded surfaces adhesive-based polyvinyl acetate (PVA). Samples Eucalyptus saligna wood species were prepared for resistance testing in trials blade glue shear rupture and tensile normal according to NBR 7190. The bonding surfaces were prepared by milling operation employing feed speed of 11.0 m/min and then by the grinding operation using five different grain sizes of sandpaper (grands: 80, 100, 120, 150 and 220). After sanding, the surfaces were subjected to measurements of roughness with roughness equipped with a diamond probe tip of cone-spherical shape, with nose radius of 2µm, together with surface analysis program. Among the results we can point out the best performances of rupture strength, shear strength for sanded surfaces by sanding the bundles 220, the normal traction surfaces sanded by sanding to 120 cash

The conformational energy differences have been determined for ethylene glycol, 2- chloroethanol, and 2,2- dichloroethanol in the neat liquid, DMSO, and H20 with Raman spectroscopy. Spectra in the 0-H valence region were utilized to determine the energy difference between interand intramolecularly hydrogen bonded species. It was found that the solvent effect on the relative stabilities of the gauche and trans rotamers of the alcohols differ significantly. The results also indicate that, unlike ethylene glycol, there is significant intramolecular hydrogen bond formation in the halogenated alcohols in the neat liquid phase. Stronger intramolecular hydrogen bond formation was observed in dichloroethanol than in 2-chloroethanol.

Este trabalho teve por objetivo obter revestimento de carbeto de silício para esferas combustíveis utilizadas em reatores nucleares do tipo FBNR, através da sinterização de SiC por reação com silício metálico (RBSiC). As matérias-primas foram moídas em moinho de bolas por 24 horas e as temperaturas utilizadas na sinterização foram de 1500° e 2000°C, durante tempos que variaram de 30 a 240 minutos. As amostras foram caracterizadas quanto a fases cristalinas, densidade, microestrutura e resistência mecânica. As peças sinterizadas a 2000°C apresentaram valores de resistência mecânica na faixa de 95 MPa, e densidade de cerca de 90% foram alcançadas, superiores aos valores encontrados para 1500°C.Foram obtidos revestimentos com as técnicas de gel casting e spin coating. A resistência mecânica desses revestimentos foi de, aproximadamente, 50% das amostras sinterizadas a 2000°C. / The aim of this work was to get covering of silicon carbide for use in nuclear fuel reactors of type FBNR, through the sintering of SiC by reaction bonded silicon carbide (RBSiC). The samples were homogenized in a ball mill and the sintering temperatures were 1500°C and 2200°C, during times that varied of 30 until 240 minutes. The product was characterized by crystalline phases, density, microstructure and mechanical resistance. The samples sintering at 2000°C had presented values of mechanical resistance around of 95 MPa, and density around 90%, better that samples sintering at 1500°C. Gel casting and Spin coating techniques had success in coverings process. The mechanical resistance of this coverings were around 50% of the samples sintering at 2000°C.

Este trabalho teve por objetivo obter revestimento de carbeto de silício para esferas combustíveis utilizadas em reatores nucleares do tipo FBNR, através da sinterização de SiC por reação com silício metálico (RBSiC). As matérias-primas foram moídas em moinho de bolas por 24 horas e as temperaturas utilizadas na sinterização foram de 1500° e 2000°C, durante tempos que variaram de 30 a 240 minutos. As amostras foram caracterizadas quanto a fases cristalinas, densidade, microestrutura e resistência mecânica. As peças sinterizadas a 2000°C apresentaram valores de resistência mecânica na faixa de 95 MPa, e densidade de cerca de 90% foram alcançadas, superiores aos valores encontrados para 1500°C.Foram obtidos revestimentos com as técnicas de gel casting e spin coating. A resistência mecânica desses revestimentos foi de, aproximadamente, 50% das amostras sinterizadas a 2000°C. / The aim of this work was to get covering of silicon carbide for use in nuclear fuel reactors of type FBNR, through the sintering of SiC by reaction bonded silicon carbide (RBSiC). The samples were homogenized in a ball mill and the sintering temperatures were 1500°C and 2200°C, during times that varied of 30 until 240 minutes. The product was characterized by crystalline phases, density, microstructure and mechanical resistance. The samples sintering at 2000°C had presented values of mechanical resistance around of 95 MPa, and density around 90%, better that samples sintering at 1500°C. Gel casting and Spin coating techniques had success in coverings process. The mechanical resistance of this coverings were around 50% of the samples sintering at 2000°C.

Fiber-reinforced composites comprise an important class of lightweight materials which are finding increasing applications in engineering structures including body components of automobiles and aircraft. Traditionally, synthetic fibers made of glass, carbon, etc. along with a polymeric resin have constituted the most common composites. However, due to environmental concern, occupational health safety considerations, higher cost, etc., research has been focused on substituting synthetic fibers, especially glass fibers with safer, economic and biodegradable natural fibers. Due to the ease of availability and affordability in terms of cost, woven jute mats, among a wide variety of natural fiber-based reinforcements, offer a good choice in combination with a suitable resin such as polyester or epoxy for fabrication of composite laminates. In structural applications, joining of parts made of jute fiber-reinforced composites (JFRCs) would be a natural requirement. Alternatives to joining processes for metals such as welding, riveting, etc. are required for composites. A joining process of high potential is adhesive bonding which has the advantages of reducing stress concentration, permitting fastening of dissimilar materials, etc. In the present study, adhesively bonded joints of JFRCs and their mechanical behavior are investigated under quasi-static and cyclic loading conditions. Initially, characterization of substrates is carried out under monotonic loading. This is followed by determination of stress- Strain curves, failure load and mean shear strength of bonded joints as functions of joint curing temperature and overlap length using a two-part structural epoxy adhesive. All tests are carried out according to relevant ASTM standards. It has been observed that higher curing temperatures give rise to only marginally high failure load and mean shear stress at failure compared to curing at room temperature. For a given curing temperature, failure load increases while mean shear strength decreases with respect to overlap length in both types of joints. As fatigue failure is a crucial consideration in design, the behavior of adhesively bonded JFRC joints is studied for the first time under cyclic loading conditions leading to the commonly-used S-N curve for characterization of failure of materials at different loading-unloading cycles. Interestingly, the fatigue strength for infinite life of adhesively bonded JFRC joints turns out to be approximately 30% of the quasi-static strength, a correlation which usually applies to materials in general. The effect of joint overlap length on fatigue life is studied and it is observed that the above relation between fatigue and quasi static strength is retained for different overlap lengths. Additionally, insights are provided into failure modes of joints under different loading conditions and for varying overlap lengths. Various empirical predictors such as exponent, power and hybrid models fitting the S-N curve are obtained and their relative efficacy (in terms of Coefficient of Determination R2, Adjusted-R2, Akaike’s Information Criterion and Residual Sum of Squares) enumerated in prediction of failure load including quasi-static failure load. As numerical simulation is an indispensable tool in designing geometrically complex structures under nonlinear conditions including failure and contact, finite element modeling of JFRC substrates, bulk adhesive and adhesively bonded joints has been investigated using implicit and explicit LS-DYNA solvers. In this context, the effects of various modeling parameters (mesh size and loading rate) and details of constitutive models capable of capturing plasticity and failure in an orthotropic composite and isotropic adhesive are discussed. Mesh size has been found to be an important parameter affecting computed results. Finally, a good correlation within ~(4% - 7%) was found between the predicted and experimental results for JFRC substrates, bulk adhesive and adhesively bonded single lap joints.

L’étude de la propagation des ondes élastiques dans des plaques présentant des défauts en surface ou en volumetrouve sa place dans divers domaines industriels (aéronautique, automobile, aérospatial,…) pour le contrôle de l’état de santé des matériaux. L’étude menée ici en ondes transversales horizontales (SH) porte plus particulièrement sur les effets de rugosité aux interfaces d’une structure tri-couche, deux plaques isotropes collées par une couche mince de colle (les interfaces entre la couche de colle et les deux plaques sont rendues rugueuses pour améliorer l’adhésion), les plaques n'étant pas obligatoirement de même nature. L’objectif à terme est de caractériser cette rugosité et par-delà d'analyserson influence sur la qualité de collage. Les rugosités peuvent être quelconques ; celles considérées ici sont soit périodiques, soit pseudo-aléatoires. Les approches retenues sont analytiques, numériques et expérimentales. L’approche analytique basée sur une formulation intégrale adaptée à la propagation en ondes SH est utilisée pour déterminer les champs de déplacements et de contraintes dans les deux plaques. L’étude numérique par éléments finis qui utilise le logiciel COMSOL donne les coefficients de transmission. L’étude expérimentale met en oeuvre des transducteurs piézoélectriques à ondes transversales pour l’émission, et un vibromètre laser en réception, l’objectif étant de générer et d’identifier les modes propagatifs dans les structures étudiées, et d’évaluer leur comportement selon le type de rugosité.Les résultats et comparaisons portent sur les champs (déplacement-contrainte) et les coefficients de transmission enprésence de rugosité, avec ou non accords de phase lorsque des périodicités apparaissent sur les profils de rugosité. / Analysing the elastic wave propagation in rough plates opens the way to several applications such as the health monitoringof materials in industrial sectors (aeronautics, automotive, aerospace,..). The study here in using shear horizontal waves(SH), focuses on the effects of roughness at the interfaces of a bi-layered structure which consists of two isotropic platesadhesively bonded using a thin layer of glue (the interfaces between the adhesive layer and the two plates are roughenedto improve adhesion), the plates being not necessarily of the same nature. The aim of this study is to characterize thisroughness and beyond to analyze its influence on the quality of bonding. The roughness may have any profile; thoseconsidered here are either periodic or pseudo-random. The approaches used are analytical, numerical and experimental. The analytical approach, based on the integral formulation developed for SH-wave propagation, is used to determine the fields of displacements and stresses in both plates. The numerical finite element analysis using the COMSOL software gives the transmission coefficients. In the experimental study, shear waves piezoelectric transducers are used for the emission and a laser vibrometer for the reception; the final aim being to generate and to identify the modes propagating in the studied structures, and to evaluate their behavior depending on the roughness. The displacement and stress perturbation maps, and transmission coefficients are presented in the presence of roughness, with or without phase-matching.

Ce travail de thèse (CIFRE, Renault) porte sur la conception, le développement et la pré-industrialisation d'un nouveau type de moteur de haut-parleur sans fer utilisant des plasto-aimants, permettant à la fois de réduire très nettement la distorsion due au moteur, ainsi que d'alléger le haut-parleur grâce à une optimisation de la masse magnétique utile.Après un rappel sur le fonctionnement du haut-parleur, sa modélisation, les différentes non-linéarités qui lui sont propres, et plus particulièrement celles liées au moteur du haut-parleur, le manuscrit présente ensuite une nouvelle structure de moteur de haut-parleur tout aimant réalisée en plasto-aimant. Plusieurs mesures réalisées sur un prototype et sur le même haut-parleur équipé du moteur standard permettent de vérifier les attentes théoriques et de quantifier les avantages et les inconvénients de ce nouveau type de moteur. Ce prototype a été réalisé sur la base d'un haut-parleur automobile standard sur lequel le moteur a été changé. Le moteur a été réalisé par Paulstra/Hutchinson puis assemblé par Faital S.p.A., deux fournisseurs automobiles certifiés. Les méthodes utilisées pour réaliser ce prototype pourraient être directement dérivées pour une production en série. / This PhD work (CIFRE, Renault) deals with the conception, development and pre-industrialization of a new kind of ironless loudspeaker motor using bonded magnets, allowing to highly reduct the distortion due to the motor, as well as making the loudspeaker lighter thanks to an optimization of the useful magnetic mass.After reminding the general laws that describe the functioning of a loudspeaker, the different intrinsic non-linearities, and more particularly those directly linked to the loudspeaker motor, this thesis presents a new ironless structure made of bonded magnet that we developed during these three years. A complete theoretical study of this new structure, presenting the magnetic model and the design of the motor, is proposed and completed with several measurements realized on a prototype and on the standard loudspeaker in order to verify the theoretical expectations, with regard to harmonic and intermodulation distortion reduction, and quantify the advantages and disadvantages of this new kind of motor. This prototype was based on the design of a standard automotive loudspeaker on which the motor was replaced by a bonded magnet motor. The motor was fabricated by Paulstra/Hutchinson and then assembled on the loudspeaker by Faital S.p.A., both of whom are certified automotive suppliers. The methods used to realize this prototype could be directly derivated for mass production. This PhD work is used by the people in charge of the development of this technology with a view to a potential industrialization for mass market.

A large inventory of low rise masonry buildings in Canada and elsewhere in the world were built using unreinforced or partially reinforced load bearing wall. The majority of existing masonry structures is deficient in resisting seismic force demands specified in current building codes. Therefore, they pose significant risk to life safety and economic wellbeing of any major metropolitan centre. Because it is not economically feasible to replace the existing substandard buildings with new and improved structures, seismic retrofitting remains to be an economically viable option. The effectiveness of surface bonded carbon fiber-reinforced polymer (CFRP) sheets in retrofitting low-rise load bearing masonry walls was investigated in the current research project. The retrofit technique included the enhancements in wall capacity in shear and flexure, as well as anchoring the walls to the supporting elements through appropriate anchorage systems. Both FRP fan type anchors and steel sheet anchors were investigated for elastic and inelastic wall response. One partially reinforced masonry (PRM) wall and one unreinforced masonry (URM) wall were built, instrumented and tested under simulated seismic loading to develop the retrofit technique. The walls were retrofitted with CFRP sheets applied only on one side to represent a frequently encountered constraint in practice. FRP fan anchors and stainless steel sheet anchors were used to connect the vertical FRP sheets to the wall foundation. The walls were tested under constant gravity load and incrementally increasing in-plane deformation reversals. The lateral load capacities of both walls were enhanced significantly. The steel sheet anchors also resulted in some ductility. In addition, some small-scale tests were performed to select appropriate anchor materials. It was concluded that ductile stainless steel sheet anchors would be the best option for brittle URM walls. Analytical research was conducted to assess the applicability of truss analogy to retrofitted walls. An analytical model was developed and load displacement relationships were generated for the two walls that were retrofitted. The analytical results were compared with those obtained experimentally, indicating good agreement in force resistance for use as a design tool.

This thesis scrutinizes theory of consignment stocks including all significant aspects connected with establishing and operating a consignment stock. Different alternatives of distribution systems of one particular company producing and selling consumer goods are specified in the research chapter. On the basis of findings recommendation for company management as well as summary of potential risks, which are linked with operating a consignment stock, are presented.

The objective of this master’s thesis is to evaluate the use of Bonded Block Modelling (BBM) in 3DEC software combined with hybrid rock bolts, for three different cases. These cases included the laboratory rock bolt case, the shearing case and the blocky rock mass case. 3DEC is a Distinct Element Method (DEM) numerical software which can be used to simulate both continuum and discontinuum media in 3D. The Bonded Block Model in 3DEC can be used to simulate a rock mass as bonded polyhedral elements. The BBM is a relatively new numerical modelling technique. Earlier studies have focused mainly on laboratory test cases and less on field scale studies. The laboratory rock bolt test was introduced by Hoek and the main idea was to describe the way that rock bolts work. Four different rock bolt spacing designs were simulated and one unsupported model, in order to validate Hoek’s results. The diameter of the blocks was 15 cm while the zones were modelled with length of 5 cm. The tunnel on the shearing case was excavated at the depth of 1500 m. For the stress field, the in-situ stresses of Kiirunavaara mine were considered. The tunnel on the blocky case was excavated at the depth of 30 m and a gravitational stress field was assumed. The shearing model as well as the blocky model, were simulated on a quasi-3D model. The zone length for both cases was 0.1 m. In both cases, a discontinuum non-BBM was modelled first and then, a discontinuum BBM with different rock UCS values was simulated. The discontinuum BBM on the shearing case was simulated for rock UCS of 200, 100, and 50 MPa, while on the blocky case, it was simulated for rock UCS of 50 MPa. The Mohr – Coulomb constitutive model was selected for all three modelling cases. The conclusions of this work were the following: –       The laboratory rock bolt model validated the results of Hoek. Hoek suggested that rock bolt spacing less than three times the average rock piece diameter would be sufficient to produce positive results. The stabilization of the rock pieces as well as the forming of the compression zone were achieved when this equation was satisfied. The geometry of the stabilized material as well as the compression zone, were also correct. –       The discontinuum BBM on the shearing case with intact rock UCS of 200 MPa, produced similar results as the discontinuum non-BBM. This indicates that BBM can be applied for these cases and produce reliable results. The displacement of the fault was expected to be higher than the resulting values. The discontinuum BBM with reduced rock strength (100 MPa and 50 MPa) resulted in rock mass fragmentation. However, the fragmented rock pieces did not detach from the rock mass as the displacement values were not high enough.   –       The discontinuum BBM on the blocky case with intact rock UCS of 50 MPa, produced similar results as the discontinuum non-BBM. There were two discontinuities that affected the smooth transition of the displacement/stress results on the different blocks. The fragmentation of the rock mass due to the existence of the discontinuities did not produce any further rock mass movements.   –       The interaction between rock mass and rock bolts was evident in any modelling case. For the laboratory rock bolt model, the hybrid bolts design was vital for producing correct results. For the shearing model, the hybrid bolts were subjected to shearing movements due to fault movements. In the blocky model, the bolts in the roof of the tunnel were subjected to axial displacements, due to the existence of blocks. The recommendations for further work were the following: –       The hybrid bolts in the laboratory rock bolt test were pretensioned only in the beginning of the computation phase. In reality, the tensioned bolts act at every moment and not only in the beginning. However, it would be interesting to see if the results are similar with continuously tensioned hybrid bolts. It is anticipated that the constantly tensioned hybrid bolts should be able to keep the compressive zones with high values throughout the whole cycling process. Thus, it is suggested for future modellers that this case could be modelled with continuously tensioned hybrid bolts. –       The installation of rock bolts in the shear case as well as in the blocky case, was at the exact same time as the tunnel was excavated.  This is not realistic fact because it is impossible to install the rock bolts exactly the same time as the tunnel excavated. Thus, it is suggested that those two cases could be modelled in the future with more focus on the stress relaxation factor.