Esta tesis tiene como objetivo evaluar un método de reforzamiento propuesto en base a la incorporación de fibras de polipropileno con la finalidad de incrementar la resistencia y mejorar las características mecánicas del suelo arcilloso de Palian – Huancayo. La arcilla es un suelo cohesivo constituido por partículas finas, estas características determinan la capacidad de deformación y compresión, además poseen baja resistencia al corte y a cargas. Debido a ello se busca reforzar y mejorar el comportamiento mecánico de la arcilla mediante métodos físicos y químicos. Esta investigación propone la adición fibras de polipropileno como método de reforzamiento para lo cual se analizó el suelo remoldeado con diferentes porcentajes de fibras adicionadas 0.1, 0.2, 0.3, 0.4 y una longitud de fibra de 10 milímetros. Se realizaron ensayos de caracterización física para identificar el suelo natural remoldeado: granulometría por sedimentación, límites de consistencia y gravedad específica de los sólidos. Se sometió el suelo natural remoldeado y las mezclas con diferentes porcentajes de fibras a los siguientes ensayos de caracterización mecánica para determinar las variaciones en el comportamiento: ensayo de compactación estándar, ensayo de corte directo y ensayo de compresión simple. Los valores obtenidos mediante los ensayos realizados demostraron la mejora de las características mecánicas del suelo siendo la mezcla de 0.4% de fibras de polipropileno la que brinda un mejor resultado en comparación con las mezclas de menor proporción. / This thesis aims to evaluate a reinforcement method based on the incorporation of polypropylene fibers to increase the strength and improve the mechanical characteristics of Palian- Huancayo’s clay soil. Clay is a cohesive soil consisting of fine particles, these characteristics determine the capacity of deformation and compression, as well as low resistance to cutting and loads. Therefore, it seeks to strengthen and improve the mechanical behavior of clay through physical and chemical methods. This research proposes the addition of polypropylene fibers as reinforcement method for which the soil under study was analyzed with different percentages of fibers added 0.1, 0.2, 0.3, 0.4 and a fiber length of 10 millimeters. Physical characterization tests were carried out to identify the natural soil: granulometry by sedimentation, limits of consistency and specific gravity of the solids. The natural soil and the mixtures with different percentages of fibers were subjected to the following mechanical characterization tests to determine the variations in behavior: Standard compaction test, unconfined compression test, and shear direct test. The values obtained through the tests demonstrated the improvement of the mechanical characteristics of the soil being the mixture of 0.4% of polypropylene fibers the one that provides a better result compared to the mixtures of a lower proportion. / Tesis

The application of thermoplastics as load-carrying components in furniture applications is an attractive prospect at IKEA. Thermoplastics can be used instead of metal where advanced geometries and aesthetics are considered. In this thesis work in solid mechanics, it is of interest to investigate different test setups proposed in the literature for compression testing of thermoplastics while taking into account the complex stress fields induced in the test samples during the compression test.  The simulations have showed that the main cause of complex stress fields in compression test specimens is the presence of friction between the specimen and the machine heads. Friction prevents perfect Poisson contractions during the test which shifts the orientation of the local stress tensors from the direction of loading. Out of the shapes investigated in this thesis, it has been concluded that cube-shaped specimens were the most suitable to utilize in compression tests. The results were based on exploiting measures that pertain to accuracy and robustness parameters within stress and strain. Furthermore, manufacturing impact and ease of test measurements were considered. / Användningen av termoplaster som lastbärande komponenter i möbelapplikationer har ökat under de senaste åren inom IKEA. Då det förutom att vara estetiskt tilltalande för hela möbler är främsta användningen i komponenter som har mer komplicerade geometrier. I detta examensarbete i hållfasthetslära är det av intresse att undersöka olika provkroppar vilket föreslås i litteratur för kompressionsprovning av termoplaster med hänsyn till de komplexa spänningstillstånden som orsakas under provning.  Simuleringarna har påvisat de komplexa spänningstillstånd i kompressionsprov som uppkommer på grund av friktion mellan provstaven och grepen. Friktion förhindrar perfekt tvärkontraktion, vilket förändrar orienteringen av de lokala spänningstensorerna från belastningsriktningen, vilket är enaxlig. Utifrån de former som undersöktes i detta examensarbete blev slutsatsen att kubformade provkroppar var de mest lämpliga att använda i kompressionsprovning. Resultaten baserades på att utnyttja åtgärder som avser noggrannhetsparametrar inom spänning och töjning men även tillverknings och provmätningens lätthet.

No description available.

Three testing methods are proposed to characterize properties of fuel cell materials that affect the mechanical durability of proton exchange membranes (PEMs). The first two methods involved measuring the in-plane biaxial strength of PEMs and the biaxial hygrothermal stresses that occur in PEMs during hygrothermal cycles. The third method investigated the nonuniform thickness and compressibility of gas diffusion media which can lead to concentrated compressive stresses in the PEM in the through-plane direction. Fatigue and creep to leak tests using multi-cell pressure-loaded blister fixtures were conducted to obtain the lifetimes of PEMs before reaching a threshold value of gas leakage. These tests are believed to be more relevant than quasi-static uniaxial tensile to rupture tests because of the introduction of biaxial cyclic and sustained loading and the use of gas leakage as the failure criterion. They also have advantages over relative humidity cycling test because of the controllable mechanical loading. Nafion® NRE-211 membrane was tested at three different temperatures and the time-temperature superposition principle was used to construct a stress-lifetime master curve. Tested at 90°C, extruded Ion Power® N111-IP membrane was found to have longer lifetime than Gore™-Select® 57 and Nafion NRE-211 membranes under the same blister pressure profiles. Bimaterial specimens fabricated by bonding a piece of PEM to a substrate material were used to measure the hygral stresses, compressive and tensile, in the PEM during relative humidity cycles. The substrate material and its thickness were carefully chosen so that stresses in the PEM could be obtained directly from the curvature of the bimaterial specimen without knowing the constitutive properties of the PEM. Three commercial PEMs were tested at 80°C by cycling the relative humidity between 90% and 0% and by drying the membrane to 0%RH after submersion in liquid water. Stress histories for all three membranes show strong time-dependencies and Nafion® NRE-211 exhibited the largest tensile stress upon drying. Besides in-plane stresses, hard spots in gas diffusion media (GDM) can locally overcompress PEMs in the out-of-plane direction and cause electrical shorting. In this study, GDM samples sealed with an impermeable Kapton® film on the surface were compressed with uniform air pressure and the nonuniform displacement field was measured with a three-dimensional digital image correlation technique. Hard spots as a result of the nonuniform thickness and compressibility of the GDM were found and their severities as stress risers are evident. Locally, a nominal platen compression (similar to bipolar plate land compression) of 0.68 MPa can lead to compressive stress as large as 2.30 MPa in various hard spots that are in the order of 100s µm to 1 mm in size. / Ph. D.

The LHC (Large Hadron Collider) will have a long shut down in the years of 2019 and 2020, referred to as LS2. During this stop the LHC injector complex will be upgraded to increase the luminosities, which will be the first step of the high luminosity LHC program (which will be realized during LS3 that takes place in 2024-2026). The LHCb experiment, whose main purpose is to study the CP-violation, will during this long stop be upgraded in order to withstand a higher radiation dose, and to be able to read out the detector at a rate of 40MHz,compared to 1MHz at present. This change will improve the trigger efficiency significantly. One of the LHCb sub-detectors the Trigger Tracker (TT), will be replaced by a new sub-detector called UT. This report presents the early stage design (preparation for mock-up building) of the box that will be isolating the new UT detector from the surroundings and to ensure optimal detector operation. Methods to fulfill requirements such as light and gas tightness, Faraday-cage behavior and condensation free temperatures, without breaking the fragile beryllium beam pipe, are established. / LHC (Large Hadron Collider) kommer under åren 2019-2020 att ha ett längre driftstopp. Under detta driftstopp så kommer LHC's injektionsanordningar att uppgraderas för att kunna sätta fler protoner i circulation i LHC, och därmed öka antalet partikelkollisioner per tidsenhet. Denna uppgradering kommer att vara första steget i "High Luminocity LHC"-programmet som kommer att realiseras år 2024-2026. LHCb-experimentet, vars främsta syfte är att studera CP-brott, kommer också att uppgraderas under stoppet 2019-2020. Framför allt så ska avläsningsfrekvensen ökas från dagens 1MHz till 40MHz, och experimentet ska förberedas för de högre strålningsdoser som kommer att bli aktuella efter stoppet 2024-2026. En av LHCb's deldetektorer, TT detektorn, kommer att bytas ut mot en ny deldetektor som kallas UT. Den här rapporten presenterar den förberedande designen av den låda som ska isolera UT från dess omgivning och försäkra optimala förhållanden för detektorn. Kraven på den isolerande lådan och tillvägagångssätt för att uppfylla dessa krav presenteras. / LHCb, LS2 and LS3 Upgrade

Este estudo tem como objetivo principal comparar estruturas de pavimentos flexíveis projetadas através dos métodos empírico do DNER e mecanístico, considerando-se alguns materiais de pavimentação utilizados na região de Campo Grande, estado do Mato Grosso do Sul. Como objetivos decorrentes, pode-se destacar a obtenção das características resilientes e de fadiga destes materiais e a proposta de um catálogo simplificado de estruturas de pavimentos para a referida região. Para a efetivação da pesquisa, foram coletados materiais típicos do subleito da região e daqueles mais utilizados na composição de bases e capas dos pavimentos locais. Após as suas caracterizações, realizaram-se ensaios de compactação, CBR, triaxiais cíclicos e compressão diametral estática e dinâmica. As análises mecanísticas foram realizadas utilizando-se o programa computacional FEPAVE, que leva em conta o comportamento elástico não-linear dos materiais, considerando-se o critério de confiabilidade. A partir da análise comparativa dos métodos de dimensionamento, observou-se que, ora as estruturas estabelecidas pelo método mecanístico são idênticas às determinadas pelo método do DNER, ora são mais esbeltas, ora são menos esbeltas, dependendo do tipo de material que constitui as camadas e do nível de confiabilidade adotado. Verificou-se ainda que a caracterização dos materiais através dos ensaios de módulo de resiliência, vida de fadiga e deformação permanente é imprescindível quando se deseja projetar um pavimento empregando-se o método mecanístico. Por fim, elaborou-se um catálogo simplificado de pavimentos flexíveis para a região de Campo Grande – MS, com as intenções de contemplar o uso de materiais locais e auxiliar os engenheiros na concepção de seus projetos / This study has as main objective to compare structures of flexible pavements designed by two different methods, the DNER empirical method and the mechanistic method, being considered some paving materials used in the area of Campo Grande, state of Mato Grosso do Sul. As secondary objectives, it can stand out the obtaining of the mechanical properties of these materials and the proposal of a simplified catalog of flexible pavements for the referred area. For the accomplishment of the research, typical materials of subgrade, base course and surface layer were collected. After their characterizations, tests of compaction, CBR and repeated load were executed. The mechanistic analyses were accomplished being used the software FEPAVE, that takes into account the non-linear resilient modulus of the materials, being considered the reliability criterion. Starting from the comparative analysis of the design methods, it was observed that the structures established by the mechanistic method can be identical, more slender or less slender to the ones obtained by the empirical method, depending on the type of the material that constitutes the layers and the reliability level adopted. It was also verified that the characterization of the materials by repeated load tests (resilient modulus, fatigue’s life and permanent deformation) is indispensable when one want to project a pavement being used the mechanistic method. Finally, a simplified catalog of flexible pavements was elaborated for the area of Campo Grande – MS, with the intentions of to contemplate the use of local materials and to aid the engineers in the conception of their projects

Este estudo tem como objetivo principal comparar estruturas de pavimentos flexíveis projetadas através dos métodos empírico do DNER e mecanístico, considerando-se alguns materiais de pavimentação utilizados na região de Campo Grande, estado do Mato Grosso do Sul. Como objetivos decorrentes, pode-se destacar a obtenção das características resilientes e de fadiga destes materiais e a proposta de um catálogo simplificado de estruturas de pavimentos para a referida região. Para a efetivação da pesquisa, foram coletados materiais típicos do subleito da região e daqueles mais utilizados na composição de bases e capas dos pavimentos locais. Após as suas caracterizações, realizaram-se ensaios de compactação, CBR, triaxiais cíclicos e compressão diametral estática e dinâmica. As análises mecanísticas foram realizadas utilizando-se o programa computacional FEPAVE, que leva em conta o comportamento elástico não-linear dos materiais, considerando-se o critério de confiabilidade. A partir da análise comparativa dos métodos de dimensionamento, observou-se que, ora as estruturas estabelecidas pelo método mecanístico são idênticas às determinadas pelo método do DNER, ora são mais esbeltas, ora são menos esbeltas, dependendo do tipo de material que constitui as camadas e do nível de confiabilidade adotado. Verificou-se ainda que a caracterização dos materiais através dos ensaios de módulo de resiliência, vida de fadiga e deformação permanente é imprescindível quando se deseja projetar um pavimento empregando-se o método mecanístico. Por fim, elaborou-se um catálogo simplificado de pavimentos flexíveis para a região de Campo Grande – MS, com as intenções de contemplar o uso de materiais locais e auxiliar os engenheiros na concepção de seus projetos / This study has as main objective to compare structures of flexible pavements designed by two different methods, the DNER empirical method and the mechanistic method, being considered some paving materials used in the area of Campo Grande, state of Mato Grosso do Sul. As secondary objectives, it can stand out the obtaining of the mechanical properties of these materials and the proposal of a simplified catalog of flexible pavements for the referred area. For the accomplishment of the research, typical materials of subgrade, base course and surface layer were collected. After their characterizations, tests of compaction, CBR and repeated load were executed. The mechanistic analyses were accomplished being used the software FEPAVE, that takes into account the non-linear resilient modulus of the materials, being considered the reliability criterion. Starting from the comparative analysis of the design methods, it was observed that the structures established by the mechanistic method can be identical, more slender or less slender to the ones obtained by the empirical method, depending on the type of the material that constitutes the layers and the reliability level adopted. It was also verified that the characterization of the materials by repeated load tests (resilient modulus, fatigue’s life and permanent deformation) is indispensable when one want to project a pavement being used the mechanistic method. Finally, a simplified catalog of flexible pavements was elaborated for the area of Campo Grande – MS, with the intentions of to contemplate the use of local materials and to aid the engineers in the conception of their projects

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-25T15:51:00Z No. of bitstreams: 1 FRANCISCO GALDINO JÚNIOR - DISSERTAÇÃO PPGEM 2014..pdf: 6213176 bytes, checksum: 50d50ccb2736f335fb4e52475cb149f7 (MD5) / Made available in DSpace on 2018-04-25T15:51:00Z (GMT). No. of bitstreams: 1 FRANCISCO GALDINO JÚNIOR - DISSERTAÇÃO PPGEM 2014..pdf: 6213176 bytes, checksum: 50d50ccb2736f335fb4e52475cb149f7 (MD5) Previous issue date: 2014-08-28 / O crescente desenvolvimento de materiais compósitos reforçados nos últimos anos tem propiciado novas alternativas para solucionar diversos problemas acerca da necessidade de novos materiais com combinações de propriedades. Para utilizarmos tais materiais, devemos realizar vários ensaios mecânicos, como: tração, compressão, flexão e principalmente de impacto. Para isso, foram realizados estudos específicos sobre materiais compósitos e impactos em estruturas laminadas. Através desses estudos e de um levantamento do estado da arte acerca do projeto de diversas máquinas de impacto por queda de peso, foi projetada e fabricada uma máquina de impacto por queda de peso para materiais compósitos de simples concepção. A máquina desenvolvida possui um intervalo de energia de impacto entre 20J e 96J, obtida através de variação da massa de queda de impacto. Foi desenvolvido também um sistema instrumentação para aquisição da força de impacto e da energia absorvida pelo corpo de prova, além de um sistema anti rebote eletromecânico. Para a validação do equipamento foram realizados ensaios de impacto por queda de peso em placas compósitas de fibra de vidro com 8, 10, 12 e 14 camadas e analisado os danos causados nas mesmas, através de software de análise de imagem. A partir de um software de análise de vídeo foi possível calcular a velocidade de impacto e a energia de impacto nos ensaios e comparar com o método teórico e o instrumentado. / The increasing development of reinforced composite materials in recent years has provided new alternatives to solve various problems about the need for new materials with combinations of properties. For such materials we use, we conduct various mechanical tests, such as tensile, compression, bending and mainly impact. For this, specific studies on composite materials, and impact on laminate structures were performed. Through these studies and a survey of state of the art about the project in several of drop impact weight machines, is designed and manufactured a machine to drop impact weight for composites of simple design. The machine has developed a range of impact energy of 20J, and 96J, obtained by varying the mass of the drop impact. One instrumentation system for the acquisition of the impact force and energy absorbed by the specimen was also developed, and an anti rebound electromechanical system. To validate the equipment impact tests were performed by weight loss in composite plates with glass fiber 8, 10, 12 and 14 layers and analyzed the damage caused in the same via image analysis software. From a software video analysis it was possible to calculate the impact velocity and impact energy in the tests and compare with the theoretical method and instrumented.

En usinage, la zone de coupe présente des conditions de température, des cinétiques thermiques, des déformations et des pressions extrêmes. Dans ce contexte, être capable de relier les variations des conditions de coupe (vitesse de coupe, avance, lubrification, usure, outil,…) à l’intégrité de la surface usinée constitue un objectif scientifique majeur. Cette thèse s’intéresse au cas du tournage finition du 15-5PH (acier inoxydable martensitique utilisé, entre autre, pour la fabrication des pièces de rotor d’hélicoptère ainsi que les pompes et les vannes de circuit primaire de centrale nucléaire) et s’inscrit dans le cadre du projet MIFSU (Modélisation de l’Intégrité et de la Fatigue des Surfaces Usinées).Dans un premier temps, le comportement du matériau a été étudié afin d’alimenter les simulations d’usinage. Des essais de dilatométrie libre ont été conduit afin de calibrer les cinétiques d’austénitisation du 15-5PH pour des vitesses de chauffe élevées (jusqu’à 11000 °C/s). Les paramètres du modèle de changement de phase de Leblond ont alors été identifiés. De plus, des essais de compression dynamique (dε/dt allant de 0.01 à 80 /s et ε > 1) ont été réalisés pour calibrer une loi de comportement élasto-plastique aux grandes déformations avec une sensibilité à la vitesse de déformation. Ces essais ont aussi permis de mettre en évidence des phénomènes de recristallisation dynamique et leurs influences sur la contrainte d’écoulement du matériau. Un modèle de recristallisation dynamique a donc également été mis en œuvre.En parallèle, un modèle numérique de prédiction de l’intégrité des surfaces tournées a été construit. Ce modèle repose sur une méthodologie dite « hybride » (développée au cours de la thèse Frédéric Valiorgue pour l’acier AISI 304L) qui consiste à supprimer la modélisation de l’outil de coupe et de la formation du copeau, et à remplacer l’impact thermomécanique de ces derniers sur la surface usinée par des chargements équivalents. Une étape de calibration de ces chargements a donc été réalisée à travers des essais de coupe orthogonale et de frottement (étude de sensibilité des efforts d’usinage, du coefficient de frottement et du coefficient de partage thermique) aux variations des paramètres de coupe.Enfin, les résultats des simulations numériques de tournage portant sur la prédiction des changements de microstructure (austénitisation et recristallisation dynamique) ainsi que des contraintes résiduelles ont été comparés aux résultats issus d’une campagne d’essais de chariotage. / During machining, extreme conditions of pressure, temperature and strain appear in the cutting zone. In this thermo-mechanical context, the link between the cutting conditions (cutting speed, lubrication, feed rate, wear, tool coating…) and the machining surface integrity represents a major scientific target. This PhD study is a part of a global project called MIFSU (Modeling of the Integrity and Fatigue resistance of Machining Surfaces) and it focuses on the finish turning of the 15-5PH (a martensitic stainless steel used for parts of helicopter rotor). Firstly, material behavior has been studied in order to provide data for machining simulations. Stress-free dilatometry tests were conducted to obtain the austenitization kinetics of 15-5PH steel for high heating rates (up to 11,000 ° C/s). Then, parameters of Leblond metallurgical model have been calibrated. In addition, dynamic compression tests (dε/dt ranging from 0.01 to 80/s and ε > 1) have been performed to calibrate a strain-rate dependent elastoplasticity model (for high strains). These tests also helped to highlight the dynamic recrystallization phenomena and their influence on the flow stress of the material. Thus, recrystallization model has also been implemented.In parallel, a numerical model for the prediction of machined surface integrity has been constructed. This model is based on a methodology called "hybrid" (developed during the PhD thesis of Frédéric Valiorgue for the AISI 304L steel). The method consists in replacing tool and chip modeling by equivalent loadings (obtained experimentally). A calibration step of these loadings has been carried out using orthogonal cutting and friction tests (with sensitivity studies of machining forces, friction and heat partition coefficients to cutting parameters variations).Finally, numerical simulations predictions of microstructural changes (austenitization and dynamic recrystallization) and residual stresses have been successfully compared with the results of an experimental campaign of turning.

Des nuances d’aciers à moyen carbone, microalliés au vanadium, ont été élaborées avec l’objectif d’obtenir de nouvelles microstructures, majoritairement constituées de ferrite aciculaire (FA). Le contrôle de la composition chimique (0.1-0.3 % V) et la vitesse de refroidissement (2.0 °Cs-1) conduit à des fractions de FA atteignant 80 %. Un paramètre empirique, le pouvoir ferritisant, P, a été introduit pour évaluer l’effet combiné de la composition chimique et de la vitesse de refroidissement sur la fraction de FA. Les caractérisations par MEB et MET montrent que la FA se développe à partir de la ferrite proeutectoïde recouvrant les inclusions de MnS. Une précipitation interphase de carbonitrures de vanadium, V(C,N), serait à l’origine d’un appauvrissement local en carbone de la matrice austénitique autour des aiguilles de FA, favorisant une germination autocatalytique. Le caractère fractal de la FA a été mis en évidence par des caractérisations morphologiques. Les dimensions fractales, D, et les longueurs de coupure ont été déterminées par la méthode de comptage de boîtes à partir d’images MEB. Des essais mécaniques isothermes-quasistatiques révèlent des propriétés mécaniques équivalentes à celles des microstructures bainitiques. Les courbes contrainte-déformation montrent un comportement mécanique de type Hollomon. Les structures de ces aciers présentent des taux de consolidation qui augmentent avec l’accroissement de la fraction de FA. Une corrélation entre les propriétés mécaniques et la dimension fractale a été établie. Ce lien s’exprime par des relations de type exponentiel : [delta]M = c exp [[alpha](D -2)] où M représente? les propriétés mécaniques (Re, Rm, etc.) et c? et ?[alpha] des constantes / Medium carbon vanadium microalloyed steels have been developed to obtain new microstructures, mainly formed of acicular ferrite (AF). Controlling the chemical composition and (0.1-0.3 % V) and the cooling rates (2.0 °Cs-1) lead to AF fractions up to 80 %. An empirical parameter, the ferritisant power, P, has been introduced to evaluate the combined effect of chemical composition and cooling conditions. Scanning (SEM) and transmission (TEM) electron microscopy investigations indicate that AF develops from proeutectoid ferrite enveloping MnS inclusions. An interphase precipitation of vanadium carbo-nitrides, V(C,N) has been identified. It is suggested that this precipitation is at the origin of carbon depletion in the austenitic matrix surrounding the AF plates. The formation of the AF is then enhanced by an autocatalytic effect. The fractal nature of AF has been determined by SEM and TEM characterisations. Fractal dimensions, D, and cut off lengths have been derived by the counting box method applied to SEM images. Mechanical tests conducted in isothermal and quasistatic conditions reveal that mechanical properties of AF are of the same grade of that of bainitic microstructures. Experimental strain-stress curves are described by the Hollomon law. The work hardening of the studied microstructures increases with the AF fraction. The mechanical properties have been linked to the fractal dimension by the following exponential relation : [delta]M = c exp [[alpha] (D -2)], where M represents the mechanical property (Re, Rm, etc.) and c and [alpha] are constants parameters