No description available.

Cette thèse s'inscrit dans un programme de développement technologique de la Société LEONI. Ce programme de recherche a pour principal objectif de disposer, à l'issue des trois années de l'étude, d'un panel de connaissances scientifiques le plus pertinent possible sur la durabilité des alliages d'aluminium dans des environnements caractéristiques d'un faisceau électrique automobile. Il s'agit, à terme, d'intégrer, à l'échelle industrielle, l'aluminium ou l'un de ses alliages dans les câblages électriques automobiles. Après une première étape de sélection des matériaux, l'alliage retenu est un alliage d'aluminium 6101. La fabrication des faisceaux électriques automobiles nécessite l'utilisation de brins de petits diamètres qui sont obtenus, à partir d'une ébauche, par un procédé de mise en forme associant plusieurs étapes de tréfilage et de revenu. Chacune de ces étapes conditionne les propriétés de l'alliage. Les travaux réalisés dans le cadre de cette thèse ont eu pour objectif d'analyser et de quantifier l'influence des différentes étapes de ce procédé de mise en forme sur la durabilité de l'alliage 6101. Compte tenu de l'environnement en service des faisceaux électriques, deux types de sollicitation ont été considérés ; ces sollicitations sont associées à un endommagement en corrosion d'une part et à un endommagement en fatigue-corrosion d'autre part. La première partie de ces travaux est donc consacrée à une étude du comportement en corrosion en milieu contenant des ions chlorures de l'alliage d'aluminium AA 6101 à l'état métallurgique T4, correspondant à l'état microstructural du matériau d'ébauche. L'influence des traitements thermomécaniques liés au procédé de mise en forme des fils fins sur la microstructure, les propriétés mécaniques et le comportement en corrosion de l'alliage AA 6101 fait l'objet de la seconde partie des travaux. Enfin, l'influence de contraintes mécaniques cycliques sur le comportement en corrosion de l'alliage AA 6101 en milieu NaCl 0,5M a été étudiée. L'ensemble de ces résultats met en évidence un couplage environnementmicrostructure-état de contraintes avec un fort impact des traitements thermo-mécaniques sur les microstructures et donc sur les propriétés mécaniques et le comportement en corrosion du matériau / This work is in the framework of a technological development program with LEONI. The aim of this program research is to bring technical skills and scientific knowledge, the most pertinent as possible on the durability of aluminum alloys in automotive harness environment. The purpose is to integrate aluminum alloys in automotive wiring systems. After a first step of materials selection, the AA 6101 aluminum alloy has been selected. Automotive wiring harnesses need small diameters of strands which are obtained by a forming process combining several cold-drawing steps and aging heat treatments. Each step of this forming process influences the alloy properties. The aim of this work is to analyze and quantify the influence of each step of the forming process on the durability of AA 6101 aluminum alloy. Considering the automotive harness environment, two kinds of damages have been studied: corrosion damage in one hand and fatigue-corrosion damages in the other hand. The first part of this work was dedicated to the study of the corrosion behavior of AA 6101 aluminum alloy at T4 metallurgical state in chloride media. The influence of thermo-mechanical treatments, due to the process forming of the strands on the microstructure, the mechanical properties and the corrosion behavior of the AA 6101 has been studied in the second part. Finally, the influence of cyclic mechanical stresses on the corrosion behavior, i.e. fatigue-corrosion phenomena, of the AA 6101 in 0.5M NaCl has been considered. The whole results highlight a coupling between environment-microstructure-stress states with a severe influence of the thermo-mechanical treatments on the microstructures, the mechanical properties and on the corrosion behavior

Self-Consolidating concrete (SCC), a highly flowable concrete, is gaining wide acceptance in the concrete industries due to a higher productivity, lower energy consumption, improved working environment and increase quality. SCC is susceptible to segregation and therefore a balance between flow-ability and stability is required. The absence of a comprehensive SCC mixture composition design guidelines merits investigating the effects of SCC mixture variables on the properties affecting its performance, namely flow and stability. An experimental and analytical study were carried out to study the influence of 5 design variables, namely water to binder ratio (w/b), percent addition of silica fume (SF), percent addition of Ground Granulated Blast Furnace Slag (GGBFS), bulk volume of coarse aggregates and binder content, on the workability and rheology of SCC. Workability measurements, specifically the slump flow, T50, L-Box and segregation column, and rheological properties, namely plastic viscosity, yield stress, and thixotropy were measured to evaluate SCC’s performance. A revised modified Bingham model was proposed to adequately account for the linear and non-linear responses of the concrete flow. It postulates that the flow is divided into a linear and non-linear part. The revised model is found to provide more consistent and precise estimate of the rheological properties. Using regression analyses, yield stress and plastic viscosity models that account for the statistically significant variables were derived from experimental test data. Yield stress is found to depend on the bulk volume fraction of the coarse aggregate, Silica Fume content, High Range Water Reducing Agent (HRWRA) and Viscosity Modifying Agent (VMA), and plastic viscosity on w/b, HRWRA and Average Paste Thickness (APT). / Thesis / Master of Applied Science (MASc)

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

In pressurised water reactors (PWRs), hydrogen overpressure is used to keep the corrosion potential below the threshold for onset of intergranular stress corrosion cracking (IGSCC) in type 304 SS. However, some regions may contain higher oxygen levels resulting in an increase in the potential. These 'dead space' regions are difficult to access and during refuelling; oxygen may become trapped in these locations. The objective of this study was to investigate the influence of PGM additions on IGSCC susceptibility of type 304 stainless steels (SS) in the sensitised state within PWRs. The work presented herein investigates several aspects of the IGSCC problem. Virgin and platinum group metal (PGM)-modified (Ru and Pd) 304 SS have been studied. Material characterisation, including microstructural, tensile properties, hardness and grain size measurements, has been conducted. Crack initiation studies using U-bend samples in autoclaves simulating PWR environments have also been performed. In addition, crack propagation studies using circumferential cracked bar (CCB) specimens under constant extension in potassium tetrathionate solutions, a well-known medium to promote IGSCC on sensitised stainless steels, have been conducted in order to evaluate cracking resistance. Electrochemical studies using model solutions for PWR chemistry (containing boric acid and lithium hydroxide) and also potassium tetrathionate were carried out to look at the influence of the PGM on the kinetics of the main electrochemical reactions. The results revealed that PGM additions appeared to reduce crack initiation on sensitised type 304 SS under oxygenated conditions in high temperature water containing sulphate and chloride. PGM-doped and standard sensitised type 304 stainless steels revealed susceptibility to IGSCC propagation in 0.01 M K2S4O6, at pH=1.5 and 25°C. Electrochemical studies in potassium tetrathionate media showed smaller anodic dissolution peaks with PGM additions and metallography indicated less intergranular attack with PGM additions. In PWR model electrolytes, PGM additions, particularly 1 wt% Ru, were shown to catalyse the oxygen reduction reaction or hydrogen oxidation reaction, depending on the oxygen /hydrogen level. Overall findings showed that Ru additions can improve the IGSCC resistance of sensitised type 304 SS in PWR, while Pd additions are less effective.

Master of Science / Department of Civil Engineering / Robert J. Peterman / This thesis details findings from testing done to determine bond and time-dependent characteristics of two lightweight concrete mixes. The lightweight mixes were tested to possibly provide a more cost-effective solution to replacing some of Kansas’ older bridges. Testing included use of a conventional lightweight mix and a self-consolidating lightweight mix. Sixteen Inverted T-beams were cast at a prestress plant to determine prestress losses that had occurred in the two lightweight mixes. These losses were compared to ACI, PCI, and AASHTO code equations. Creep and shrinkage prisms were also cast and measured to accurately determine creep and shrinkage variables for the two lightweight mixes. Twelve flexural beams were also cast at the prestress plant and tested at Kansas State University’s Civil Engineering Structures Laboratory to experimentally test development lengths of the lightweight mixes and to compare results with ACI code equations. This study found compressive strengths of the lightweight concrete mixes varied greatly from laboratory testing. Low concrete strengths caused the prestress losses to be greater than the predicted code values. Flexure beam testing showed several of the beams were subject to strand slip, causing a sudden violent failure.

No description available.

L’état de surface des vis de liaison des internes de cuve du circuit primaire des REP (Réacteurs à Eau Pressurisée) en 316L en service correspond à une finition d’usinage par rectification. Ces vis sont affectées par l’IASCC (Corrosion Sous contrainte Assistée par l’Irradiation). Le processus d’amorçage de la fissuration est fonction de l’oxydation externe, de l’état de surface et des interactions de la couche d’oxyde avec la localisation de la plasticité. Un des objectifs de cette étude est déterminer l’influence de la préparation de surface sur la cinétique de croissance des couches d’oxyde et la réactivité de surface en général des nuances de type 304, 316 exposées en milieu primaire des REP à 340°C. Le second objectif est de déterminer l’influence de la localisation de la déformation sur la CSC (Corrosion Sous Contraintes) des aciers inoxydables austénitiques en milieu primaire des REP. En effet, la microstructure représentative de ces nuances irradiées correspond à une microstructure à déformation localisée dans des bandes de déformation dépourvues de défauts d’irradiation. Afin de reproduire cette microstructure représentative sur le matériau modèle de l’étude (l’acier austénitique inoxydable A286 durci par la précipitation de la phase γ’ Ni3(Ti,Al)) sans avoir recours à l’irradiation, des essais de fatigue oligocyclique à Δε/2 imposée sont réalisés. Durant le cyclage mécanique (après les premiers cycles de durcissement), les précipités sont dissouts dans des bandes de glissement menant à la localisation de la déformation. Une fois les conditions expérimentales en fatigue oligocyclique permettant d’obtenir la microstructure de déformation désirée déterminées, les interactions bandes de déformation / oxyde de surface sont étudiées en oxydant des coupons pré déformés contenant des bandes de déformation et des coupons non déformés. La préparation de surface des coupons est identique. Les essais de traction lente à une vitesse de déformation de 8 x 10-8/s sont également réalisés sur des éprouvettes pré déformées et non déformées. Les résultats ont montré que la préparation de surface modifie la microstructure du métal sous la couche d’oxyde, conduisant à un ralentissement de la cinétique de croissance de la couche d’oxyde. La préparation de surface induit cependant une accélération du développement de pénétrations d’oxydes dans le métal sous la couche d’oxyde. Ainsi, sur les échantillons rectifiés, la zone recristallisée sous la couche d’oxyde est plus profonde que sur les échantillons polis (jusqu’à 1,5μm contre 500nm au maximum sur les échantillons polis) et la couche d’oxyde est plus fine que sur les échantillons polis, tandis que les pénétrations d’oxyde sont présentes sur près de 1μm de profondeur en sous couche (contre 300nm sur les échantillons polis). Nous montrons que la zone de recristallisation induite par la préparation de surface ne permet pas l’observation des interactions entre les bandes de déformation générées dans le volume par la fatigue oligocyclique et la couche d’oxyde en surface. De fait, la réactivité de surface est très importante pour l’étude de la CSC des aciers inoxydables en milieu primaire des REP. Nous avons également démontré que cette nuance était très sensible à la corrosion intergranulaire en milieu REP à 340°C. Enfin, la localisation de la déformation plastique ne semble pas favoriser la CSC sur cette nuance à cette vitesse de déformation. / The surface conditions of the 316L screw connecting vessel internals of the primary circuit of PWR (pressurized water reactor) corresponds to a grinding condition. These screws are affected by the IASCC (Irradiation Assisted Stress Corrosion Cracking). Initiation of cracking depends on the surface condition but also on the external oxidation and interactions of oxide layer with the deformation bands. The first objective of this study is to point the influence of surface condition on the growth kinetic of oxide layer, and the surface reactivity of 304, 316 stainless steel grade exposed to PWR primary water at 340 ° C. The second objective is to determine influence of strain localization on the SCC of austenitic stainless steels in PWR primary water. Indeed, the microstructure of irradiated 304, 316 grades correspond to a localized deformation in deformation bands free of radiation defects. In order to reproduce that microstructure without conducting irradiations, low cycle fatigue tests at controlled stain amplitude are implemented for the model material of the study (A286 austenitic stainless steel hardened by the precipitation of phase γ ‘Ni 3 (Ti, Al)). During the mechanical cycling (after the first hardening cycles), the precipitates are dissolved in slip bands leading to the localization of the deformation. Once the right experimental conditions in low cycle fatigue obtained (for localized microstructure), interactions oxidation / deformation bands are studied by oxidizing pre deformed samples containing deformation bands and non deformed samples. The tensile tests at a slow strain rate of 8 x 10-8 /s are also carried out on pre deformed samples and undeformed samples. The results showed that surface treatment induces microstructural modifications of the metal just under the oxide layer, leading to slower growth kinetics of the oxide layer. However, surface treatment accelerates development of oxides penetrations in metal under the oxide layer. As example, for grinded samples, the recrystallized area under the oxide layer, induced by surface treatment, is deeper than for polished sample (up to 1.5 microns vs 500 nm for the polished samples) and the oxide layer is thinner than on the polished samples, while the penetrations oxide are expands on nearly 1μm under the oxide layer (against 300nm for the polished samples). We also show that the area recrystallization resulting from surface treatment, does not allow observing the interactions between the deformation bands in the bulk generated by LCF and the oxide layer at surface. Actually, surface reactivity is strongly important for SCC study of stainless steels in PWR primary water. We also demonstrated that this grade was very sensitive to intergranular corrosion in PWR environment at 340 ° C. Finally, localization of plastic deformation does not seem to favor SCC in our A-286 grade, at that strain rate level

The objective of my study was to analyse the factors negatively influencing a somatic cell count (SCC) in raw cow´s milk. Milk samples were tested in three breeds with different technology of breeding and milking for a time period of three years. The SCC values were determined by Fluoro-opto-electronic method on a Fossomatic apparatus. Significant factor influencing SCC was quality practise hygiene of mammary gland. The lowest average values of SCC were determined in breed where was practise thoroughly hygiene of mammary gland (avarage SCC in year 2006 was 223,3.103 SB.ml-1). Next factors negatively influencing SCC were age of cows, annual period, quality of feed and frequency exchanges a udder sleeve. Influence a technology of breeding, milking and size breed on somatic cell count in milk was not extended.

This research studies the properties of self-compacting concrete by applying bamboo-charcoal to improve the fresh concrete property, physical property and micro-scale property.Conventionally, the Pozzolanic materials used in the self-compacting concrete are fly ash and slag. They are used to replace part of the cement such that the flowing property and compacting property can reach the requirement of the self-compacting concrete. According to previous research the bamboo-charcoal can absorb part of water, and enhance the early strength of concrete. In this study, we use bamboo-charcoal to replace parts of the fine-aggregate in the mixture of self-compacting concrete. The replacement ratio is designed as 0‰,2‰,3‰,3.5‰,4‰ and 5‰. From the experimental test of fresh concrete property, we can evaluate whether the concrete mix design can achieve the requirements of self-compacting concrete. Test for the compressive strength development, water absorption and rapid chloride penetration test are performed to evaluate the physical property of concrete. In addition, the scanning electronic microscope photos are taken to examine the microstructure of the concrete. In our results, it is found that the best proportion of replacement is 3‰. The requirements of self-compacting concrete can be satisfied, and the development of strength is also good.