O presente trabalho teve como objetivo a determinação das melhores condições para a remoção da adstringência de caqui Giombo, com relação à temperatura, concentrações e tempos de exposição ao etanol, além de uso da atmosfera modificada em embalagens plásticas. As melhores combinações foram utilizadas para remoção de adstringência sucedida de armazenamento refrigerado com o objetivo de prolongar o período de oferta dos frutos e a manutenção da qualidade. Para isso, foram realizados 4 experimentos. No primeiro, foram avaliados doses e tempos de exposição ao etanol, sendo os frutos expostos a 1,75mL kg-1 por 12 ou 24hs; e 3,50mL kg-1 por 12 e 24hs antes de serem armazenados a 1ºC por 20 dias. No segundo experimento, foram avaliadas temperaturas de armazenamento, sendo elas 5ºC, 10ºC e 15ºC, para remoção da adstringência utilizando-se a melhor concentração e tempo de exposição ao etanol do experimento anterior (1,75mL kg-1 por 12hs). O terceiro experimento consistiu na utilização da atmosfera modificada na remoção da adstringência. Os frutos foram selados a vácuo em diferentes filmes plásticos: polietileno de baixa densidade (PEBD), polipropileno (PP) e polinylon (PN), todos com 20µm de espessura, e mantidos embalados por 3 e 5 dias a 22ºC. No quarto experimento, utilizou-se da melhor dose de etanol (1,75mL kg-1 por 12hs), melhor embalagem selada a vácuo (PN) e subsequente armazenamento refrigerado por 30, 60 e 90 dias a 5ºC. A aplicação de 1,75mL kg-1 por período de 12hs mostrou-se suficiente para remoção total da adstringência de caquis. As temperaturas de 5ºC, 10ºC e 15ºC não são recomendáveis para a aplicação de etanol com o objetivo de remover a adstringência dos caquis. O uso de PN é eficiente na remoção da adstringência de caqui Giombo, sendo que os frutos acondicionados neste filme podem ser armazenados até 90 dias a 5ºC. / This study aimed to determine the best conditions for astringency removal of \'Giombo\' persimmon with respect to temperature, concentration and exposure time to ethanol, and use of modified atmosphere in plastic films. The best combinations were used to remove the astringency of cold storage in order to extend the shelf life of fruit. For this purpose, 4 experiments were performed. In the first study were evaluated doses and times of exposure of fruit to ethanol. Fruit were exposed to 1.75mL kg -1 by 12 or 24hs, and 3.50mL kg -1 by 12 or 24hs. After, fruit were stored at 1ºC for 20 days. In the second experiment, cold storage temperatures (5ºC, 10ºC and 15°C) were evaluated for astringency removal using the optimal concentration and exposure time to ethanol in the previous experiment (1.75mL kg -1 for 12hs). The third experiment consisted in the use of modified atmosphere in the astringency removal. The fruit were vacuum sealed in plastic films: low density polyethylene (LDPE), polypropylene (PP) and polinylon (PN), all with 20m thick, and maintained in these conditions for 3 and 5 days at 22°C. In the fourth experiment, the best dose of ethanol (1.75mL kg -1 for 12hs) and package (PN) were used and fruit were cold stored for 30, 60 and 90 days at 5°C. The application of 1.75mL kg -1 per 12hs period was sufficient to astringency removal of persimmons. The temperatures of 5ºC, 10ºC and 15ºC are not recommended for application of ethanol in order to astringency remove of persimmons. The use of PN is effective in removing astringency in \'Giombo\' persimmon, and the fruit packed in this film may be stored until 90 days at 5ºC.

La projection à froid, aussi appelée cold spray, est considérée comme un nouveau membre de la famille de laprojection thermique depuis une trentaine d'années maintenant. Cette thèse propose d'étudier le comportement endéformation des particules et du substrat et de mettre en avant les liaisons formées dans le revêtement par deuxapproches complémentaires, expérimentale et de simulation.Une méthode innovante pour observer directement la surface fracturée des particules déposées après décollementdu substrat a été testée avec succès. Par ce moyen, la surface de contact entre particule et substrat sousdifférentes conditions a été analysée.Concernant les résultats expérimentaux, une nouvelle théorie a été proposée pour expliquer le mécanisme deliaison interfaciale d'un revêtement dur de Ni sur substrat mou d'Al reposant sur l'effet de martelage répété desparticules, sur l'effet de pression du gaz principal et sur l'effet de préchauffage du substrat. La transformation dumécanisme de liaison revêtement/substrat au cours de la construction du dépôt a été mise en évidence en passantdu verrouillage mécanique à une combinaison d'une liaison mécanique et d'une liaison métallurgique, puis à laformation d'instabilités sous forme d'un mélange tourbillonnaire à l'interface. Plus de zones de liaisonsmétallurgiques sont générées sous forte pression, une plus grande déformation plastique apparaît grâce latempérature de préchauffage, et une adhérence plus forte au sein des dépôts est capable de se produire en dépitde la présence d'un film d'oxyde épais sur la surface du substrat. / Cold spraying, also called cold gas dynamic spraying, is a new coating technology which has been developed duringthe past three decade. In this study, a comprehensive investigation on particle deformation behavior and bondingbehavior between particle and substrate was conducted by experiment and numerical method.This thesis aims at presenting an innovative method to directly observe the fractured contact surface between thecold sprayed particle and substrate. By this means, the particle/substrate fractured contact surfaces were analyzedfor different conditions.Based on the experimental results, a new theory was proposed to explain the interfacial bonding mechanism of hardNi coating onto soft Al substrate. It is assumed that the particle peening effect is essential for the formation ofdiscontinuous metallurgical bonding. The dominant coating/substrate bonding mechanism is responsible of thetransformation during the coating build-up process of the initial mechanical interlocking to a combination ofmechanical interlocking and metallurgical bonding therefore of the formation of interfacial instabilities. The highcontact pressure is the relevant factor determining the particle/substrate metallurgical bonding. More metallurgicalbonding areas were generated due to strengthen peening effect of the subsequently deposited particles with higherpropelling gas pressure. Finally, stronger adhesion is able to occur despite the presence of a thick oxide film on thesubstrate surface by the preheating of the substrate. Higher temperatures help the materials to undergoes astronger plastic deformation that disrupts the oxide films. That leads to initiate an intimate contact between particleand substrate.

The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out a limited experimental program on three-point bending (TPB) masonry panels and to develop a time-dependent fracture formulation for the study of mode I fracture in quasi-brittle materials. A micro-model for fracture in unreinforced masonry is developed using the concept of the discrete crack approach. All basic masonry failure modes are taken into account. To capture brick diagonal tensile cracking and masonry crushing, a linear compression cap is proposed with a criterion for defining the compression cap. The failure surface for brick and brick-mortar interfaces are modelled using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. The fracture formulation, in nonholonomic rate form within a quasi-prescribed displacement approach, is based on a piecewise-linear constitutive law and is in the form of a so-called ?linear complementarity problem? (LCP). The proposed model has been applied to simulating fracture in masonry shear walls and masonry TPB panels. An experimental program was undertaken to investigate the failure behaviour of masonry panels under TPB with relatively low strength mortar. The basic material parameters were obtained from compression, TPB and shear tests on bricks, mortar and brick-mortar interfaces. The experimental results showed that the failure of masonry TPB panels is governed by both tensile and shear failure rather than just tensile failure. The simulation of the masonry TPB tests compared well with the experimental results. In addition, the LCP fracture formulation is enhanced to study the time-dependent mode I fracture in quasi-brittle materials. Two main time-dependent sources, the viscoelasticity of the bulk material and the crack rate dependent opening, are taken into account. A simplified crack rate model is proposed to include the rate-dependent crack opening. The model is applied to predicting time-dependent crack growth in plain concrete beams under sustained loading. The model captures the essential features including the observed strength increase with loading rate, the load-deflection and load-CMOD responses, the deflection-time and CMOD-time curves, the predicted time to failure and the stress distributions in the fracture zone.

The temperature rise at the interface of two sliding bodies has significant bearing on the friction and wear characteristics of the bodies. The friction heat generated at the interface can be viewed as "loss of exergy" of the system, which also leads to accelerated wear in the form of oxidation, corrosion, and scuffing. This has a direct impact on the performance of the components or the machinery. If the sliding interface is also conducting electric current then the physics at the interface becomes complicated. The presence of electrical current leads to Joule heat generation at the interface along with other effects like electromotive, electroplasticity, stress relaxation and creep. The interface of an electrical contact, either stationary or dynamic, is a complex environment as several different physical phenomena can occur simultaneously at different scales of observations. The main motivation for this work stems from the need to provide means for accurate determination or prediction of the critical contact parameters viz., temperature and contact resistance. Understanding the behavior of electrical contacts both static and dynamic under various operating conditions can provide new insights into the behavior of the interface. This dissertation covers three major topics: (1) temperature rise at the interface of sliding bodies, (2) study on static electrical contacts, and (3) study of factors influencing behavior of sliding electrical contacts under high current densities. A model for determining the steady-state temperature distribution at the interface of two sliding bodies, with arbitrary initial temperatures and subjected to Coulomb and/or Joule heating, is developed. The model applies the technique of least squares regression to apply the condition of temperature continuity at every point in the domain. The results of the analysis are presented as a function of non-dimensional parameters of Peclet number, thermal conductivity ratio and ellipticity ratio. This model is first of its kind and enables the prediction of full temperature field. The analysis can be applied to a macro-scale contact, ignoring surface roughness, between two bodies and also to contact between two asperities. This analysis also yields an analytical expression for determining the heat partition between two bodies, if the Jaeger's hypothesis of equating average temperatures of both the bodies is being implemented. In general for design purposes one is interested in either the maximum or the average temperature rise at the interface of two sliding bodies. Jaeger had presented simple equations, based on matching the average temperatures of both bodies, for square and band shaped contact geometries. Engineers since then have been using those equations for determining the interface temperature for circular and elliptical shaped contact geometries. Curve fit equations for determining the maximum and the average interface temperature for circular and elliptical contact with semi-ellipsoidal form of heat distribution are presented. These curve fit equations are also applicable for the case when both the bodies have dissimilar initial bulk temperatures. The equations are presented in terms of non-dimensional parameters and hence can easily be applied to any practical scenario. The knowledge of electrical contact resistance between two bodies is important in ascertaining the Joule heat generation at the interface. The prediction of the contact resistance thus becomes important in predicting the performance of the contact or the machinery where the contact exists. The existing models for predicting ECR suffer from the drawback of ambiguity of the definition of input parameters as they depend on the sampling resolution of the measuring device. A multi-scale ECR model which decomposes the surface into its component frequencies, thus capturing the multi scale nature of rough surfaces, is developed to predict the electrical contact resistance. This model, based on the JS multi-scale contact model, overcomes the sensitivity to sampling resolution inherent in many asperity based models in the literature. The multi-scale ECR model also offers orders of magnitude of savings in computation time when compared to deterministic contact models. The model predictions are compared with the experimental observations over a wide range of loads and surface roughness of the specimens, and it is observed that the model predictions are within 50% of the experimental observations. The effect of current cycling through static electrical contact is presented. It is observed that, the voltage drop across the contact initially increases with current until a certain critical voltage is increased. Beyond this critical point any increase in the current causes essentially no increase in steady-state contact voltage. This critical voltage is referred to as "saturation voltage." The saturation voltage for Al 6061 interface is found to be in the range of 160 - 190 mV and that for Cu 110 interface is in the range of 100 - 130 mV. The effect of load and surface roughness on voltage saturation is also demonstrated experimentally. An explanation based on the softening of the interface, due to temperature rise, is proposed rather than more widely referred hypothesis of recrystallization. The phenomenon of voltage saturation is also demonstrated in sliding electrical contacts. The behavior of sliding interfaces of aluminum-copper (Al-Cu) and aluminum-aluminum (Al-Al) are analyzed under high current densities. Experimental results are presented that demonstrate the influence of load, speed, current and surface roughness on coefficient of friction, contact voltage, contact resistance, interface temperature and wear rate. The experimental results reveal that thermal softening of the interface is the primary reason for accelerated wear under the test conditions. The results from the experiments presents an opportunity to form constitutive equations which could be used to predict the performance of the contact based on input parameters. The fusion of the findings of this dissertation provide methodologies along with experimental tools and findings to model, study and interpret the behavior of electrical contacts.

The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out a limited experimental program on three-point bending (TPB) masonry panels and to develop a time-dependent fracture formulation for the study of mode I fracture in quasi-brittle materials. A micro-model for fracture in unreinforced masonry is developed using the concept of the discrete crack approach. All basic masonry failure modes are taken into account. To capture brick diagonal tensile cracking and masonry crushing, a linear compression cap is proposed with a criterion for defining the compression cap. The failure surface for brick and brick-mortar interfaces are modelled using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. The fracture formulation, in nonholonomic rate form within a quasi-prescribed displacement approach, is based on a piecewise-linear constitutive law and is in the form of a so-called ?linear complementarity problem? (LCP). The proposed model has been applied to simulating fracture in masonry shear walls and masonry TPB panels. An experimental program was undertaken to investigate the failure behaviour of masonry panels under TPB with relatively low strength mortar. The basic material parameters were obtained from compression, TPB and shear tests on bricks, mortar and brick-mortar interfaces. The experimental results showed that the failure of masonry TPB panels is governed by both tensile and shear failure rather than just tensile failure. The simulation of the masonry TPB tests compared well with the experimental results. In addition, the LCP fracture formulation is enhanced to study the time-dependent mode I fracture in quasi-brittle materials. Two main time-dependent sources, the viscoelasticity of the bulk material and the crack rate dependent opening, are taken into account. A simplified crack rate model is proposed to include the rate-dependent crack opening. The model is applied to predicting time-dependent crack growth in plain concrete beams under sustained loading. The model captures the essential features including the observed strength increase with loading rate, the load-deflection and load-CMOD responses, the deflection-time and CMOD-time curves, the predicted time to failure and the stress distributions in the fracture zone.

O presente trabalho teve como objetivo a determinação das melhores condições para a remoção da adstringência de caqui Giombo, com relação à temperatura, concentrações e tempos de exposição ao etanol, além de uso da atmosfera modificada em embalagens plásticas. As melhores combinações foram utilizadas para remoção de adstringência sucedida de armazenamento refrigerado com o objetivo de prolongar o período de oferta dos frutos e a manutenção da qualidade. Para isso, foram realizados 4 experimentos. No primeiro, foram avaliados doses e tempos de exposição ao etanol, sendo os frutos expostos a 1,75mL kg-1 por 12 ou 24hs; e 3,50mL kg-1 por 12 e 24hs antes de serem armazenados a 1ºC por 20 dias. No segundo experimento, foram avaliadas temperaturas de armazenamento, sendo elas 5ºC, 10ºC e 15ºC, para remoção da adstringência utilizando-se a melhor concentração e tempo de exposição ao etanol do experimento anterior (1,75mL kg-1 por 12hs). O terceiro experimento consistiu na utilização da atmosfera modificada na remoção da adstringência. Os frutos foram selados a vácuo em diferentes filmes plásticos: polietileno de baixa densidade (PEBD), polipropileno (PP) e polinylon (PN), todos com 20µm de espessura, e mantidos embalados por 3 e 5 dias a 22ºC. No quarto experimento, utilizou-se da melhor dose de etanol (1,75mL kg-1 por 12hs), melhor embalagem selada a vácuo (PN) e subsequente armazenamento refrigerado por 30, 60 e 90 dias a 5ºC. A aplicação de 1,75mL kg-1 por período de 12hs mostrou-se suficiente para remoção total da adstringência de caquis. As temperaturas de 5ºC, 10ºC e 15ºC não são recomendáveis para a aplicação de etanol com o objetivo de remover a adstringência dos caquis. O uso de PN é eficiente na remoção da adstringência de caqui Giombo, sendo que os frutos acondicionados neste filme podem ser armazenados até 90 dias a 5ºC. / This study aimed to determine the best conditions for astringency removal of \'Giombo\' persimmon with respect to temperature, concentration and exposure time to ethanol, and use of modified atmosphere in plastic films. The best combinations were used to remove the astringency of cold storage in order to extend the shelf life of fruit. For this purpose, 4 experiments were performed. In the first study were evaluated doses and times of exposure of fruit to ethanol. Fruit were exposed to 1.75mL kg -1 by 12 or 24hs, and 3.50mL kg -1 by 12 or 24hs. After, fruit were stored at 1ºC for 20 days. In the second experiment, cold storage temperatures (5ºC, 10ºC and 15°C) were evaluated for astringency removal using the optimal concentration and exposure time to ethanol in the previous experiment (1.75mL kg -1 for 12hs). The third experiment consisted in the use of modified atmosphere in the astringency removal. The fruit were vacuum sealed in plastic films: low density polyethylene (LDPE), polypropylene (PP) and polinylon (PN), all with 20m thick, and maintained in these conditions for 3 and 5 days at 22°C. In the fourth experiment, the best dose of ethanol (1.75mL kg -1 for 12hs) and package (PN) were used and fruit were cold stored for 30, 60 and 90 days at 5°C. The application of 1.75mL kg -1 per 12hs period was sufficient to astringency removal of persimmons. The temperatures of 5ºC, 10ºC and 15ºC are not recommended for application of ethanol in order to astringency remove of persimmons. The use of PN is effective in removing astringency in \'Giombo\' persimmon, and the fruit packed in this film may be stored until 90 days at 5ºC.

Made available in DSpace on 2014-08-20T13:42:10Z (GMT). No. of bitstreams: 1 Tese_Edson_Luiz_Souza.pdf: 1398766 bytes, checksum: 1a498f2647f09c76016fa44505785cf9 (MD5) Previous issue date: 2010-06-02 / Among the most common problems mentioned by traders of 'Fuyu' persimmon, are physiological disorders, such as epidermal browning, degeneracy and pulp firmness reduction. But we still do not have available a quantification of these problems, either the causes or preventive measures. In this context, during the 2007-2010 period was carried out a series of experiments in order to: 1) perform diagnosis, at least in part, of persimmons quality of this cultivar produced in the states of SC, PR, RS; 2) assess technological responses by applying nitrogen (N) at pre-harvest, a practice commonly employed to increase productivity, 3) monitor changes in sugar accumulation and its correlation with the production region and the occurrence of skin cracks and 4) study the acclimation effect of fruits before cold storage as a means to induce increased tolerance to cold. Of this set of experiments we observed that indeed there are significant physiological disorders in 'Fuyu' persimmons, but the exact cause was not put in evidence. Probably, this is a multifactorial response resulting from the mineral nutrition, weather conditions and plant management. Regarding N suplementation, it was found that this macronutrient contributes to the increasing on number of fruits per plant and productivity, without compromising the overall quality, except the color that remains less orange and the decrease in pulp firmness at higher doses. When compared to fruit 'Fuyu' persimmon orchards with different altitudes, it was found that those from higher altitudes accumulate higher concentrations of sugars, including sorbitol, detecting a higher incidence of skin cracks. Finally, it was shown that the persimmons acclimation at 23 ± 3 °C for two days be fore the cold storage stimulates a higher accumulation of putative genes transcripts of HSPs cytosolic, mitochondrial, chloroplastic and of endomembranes transport system, higher accumulation of expansins and enzymes involved in cell wall solubilization, resulting in an appropriate evolution of ripening after refrigerated storage. These results bring a significant contribution to the technological knowledge in order that it is a treatment pre-storage, easily applied by producers and hosts of persimmons. / Dentre os problemas mais frequentemente citados pelos armazenadores de caquis Fuyu , destacam-se a ocorrência de distúrbios fisiológicos como o escurecimento epidérmico, a degenerescência e a redução da firmeza de polpa. Porém, ainda não se tem disponível a quantificação desses problemas, tampouco as causas, ou medidas preventivas. Nesse contexto, durante o período de 2007 a 2010 foi conduzido um conjunto de experimentos de modo a: 1) realizar diagnóstico, ao menos parcial, da qualidade dos caquis dessa cultivar produzidos nos estados de SC, PR e RS; 2) avaliar respostas tecnológicas à aplicação de nitrogênio (N) na pré- colheita, prática comumente empregada para aumentar produtividade; 3) monitorar a evolução do acúmulo de açúcares correlacionando-a com a região de produção e ocorrência de fissuras epidérmicas; e, 4) estudar o efeito da aclimatação dos frutos antes do armazenamento refrigerado como meio de se induzir maior tolerância ao frio. Desse conjunto de experimentos observou-se que efetivamente há significativa ocorrência de distúrbios fisiológicos em caquis; Fuyu , mas a causa exata não foi posta em evidência. Provavelmente trata-se de uma resposta multifatorial, resultante de desiquilíbrio da nutrição mineral, condições do clima e manejo da planta. No que tange à suplementação de nitrogênio, verificou-se que esse macronutriente contribui para o aumento do número de frutos por planta e a produtividade, sem comprometer a qualidade geral, exceto a coloração que se mantém menos alaranjada e a diminuição da firmeza de polpa em doses mais elevadas. Quando se compararam frutos de caqui Fuyu de pomares com altitudes distintas, verificou-se que aqueles provenientes de maiores altitudes acumulam maiores teores de açúcares, e inclusive sorbitol, detectando-se maior incidência de fissuras na epiderme. Finalmente, demonstrou-se que a aclimatação de caquis a 23 ± 3 °C por dois dias antes do armazenamento refrigerado estimula um maior acúmulo de transcritos de genes putativos de HSPs citosólicos, mitocondriais, cloroplásticos e do sistema de transporte endomembranário, maior acúmulo de expansinas e enzimas envolvidas na solubilização da parede celular, resultando numa adequada evolução da maturação após a estocagem refrigerada. Esses resultados trazem uma significativa contribuição para o conhecimento tecnológico, tendo em vista que se trata de um tratamento pré-armazenamento, facilmente aplicável pelos produtores e armazenadores de caquis.

Abstract Most of the iron in the world is produced using a blast furnace process, which has iron ore (iron oxides) and coke as its raw materials. When pellets are used in a blast furnace, the iron burden material is charged in the form of pellets and fine, iron-rich by-products are charged typically in the form of cold-bonded briquettes at the top of the blast furnace. Coke is the primary fuel and reductant in the blast furnace. Coke reacts with the oxygen of the blast air and forms carbon monoxide in the up-flowing gas, which reduces the descending iron oxide burden. In addition, carbon and hydrogen bearing reductants are injected from the tuyeres in the lower part of the furnace. Hydrogen partially replaces the carbon monoxide as a reducing agent and changes the composition of the reducing gas. The high temperature properties of the burden have a significant effect on the flow of reducing gas and formation of the cohesive zone which markedly affect the furnace efficiency. The raw materials are commonly stored outdoors and therefore include moisture in varying amounts. In addition, the briquette contains chemically bound water. The rate of injected reductants, the high temperature properties and the water content of the raw materials have significant effects on blast furnace performance. They cause various phenomena in the blast furnace which set limitations on the process. The limiting phenomena related to the use of pellets in the blast furnace were studied in this doctoral thesis with the aim of obtaining additional knowledge about the limiting phenomena. The results show that hydrogen increases the reduction rate of iron oxides at temperatures below 850 °C. High water vapour concentration causes a rapid conversion through a catalysed water-gas shift reaction at above 300 °C in a gas mixture similar to the one in the upper part of the blast furnace. The reduction rate of the cold-bonded briquette is higher than pellets due to a self-reducing effect. The phase transformations occurring in the briquette during reduction follow the path of phase equilibria. The softening of the pellet is caused by the formation of melt which initiates wüstite dissolution in the surrounding slag phase. / Tiivistelmä Suurin osa maailmassa valmistettavasta raudasta tuotetaan masuuniprosessilla, jonka pääraaka-aineita ovat rautarikaste eli raudan oksidit ja koksi. Masuunissa, jossa käytetään pellettiä, rautarikaste panostetaan pelletin muodossa ja hienojakeiset rautapitoiset sivutuotteet tyypillisesti kylmäsidottuna brikettinä masuunin huipulta. Koksi on masuunin pääasiallinen polttoaine ja pelkistin, joka masuunin sisään puhallettavan ilman hapen kanssa reagoidessaan muodostaa ylöspäin virtaavaan kaasuun hiilimonoksidia, joka pelkistää masuunin kuilussa vajoavat rautaoksidit. Lisäksi yleensä käytetään hiiltä ja vetyä sisältäviä pelkistysaineita, jotka injektoidaan masuuniin alaosan hormeilta. Vety korvaa osittain hiilimonoksidia rautaoksidien pelkistimenä ja muuttaa pelkistävän kaasun koostumusta. Panosmateriaalien korkealämpötilaominaisuudet vaikuttavat suuresti kuilun kaasuvirtauksiin ja koheesiovyöhykkeen muodostumiseen masuunissa, mitkä vaikuttavat merkittävästi masuunin tehokkuuteen. Suurista määristä johtuen raaka-aineet varastoidaan usein ulkona, joten ne sisältävät kosteutta vaihtelevissa määrin. Lisäksi briketti sisältää kemiallisesti sitoutunutta vettä. Injektoitavien pelkistysaineiden käyttömäärällä, raaka-aineiden korkealämpötilaominaisuuksilla ja vesipitoisuudella on merkittäviä vaikutuksia masuunin toimintaan. Ne aikaansaavat masuunissa erilaisia ilmiöitä, jotka asettavat prosessille rajoituksia. Tässä väitöskirjassa tutkittiin näitä masuunille rajoituksia asettavia ilmiöitä ja pyrittiin lisäämään tietämystä niistä. Tulokset osoittavat, että vety nopeuttaa rautaoksidien pelkistymistä alle 850 °C lämpötilassa. Suuri vesihöyrymäärä johtaa nopeaan konversioon masuunin yläkuilun aluetta vastaavassa kaasuseoksessa yli 300 °C lämpötilassa katalysoidun vesikaasun siirtoreaktion kautta. Kylmäsidottu briketti pelkistyy pellettiä nopeammin itsepelkistymisen vaikutuksesta. Briketin pelkistyessään läpikäymät faasitransformaatiot seuraavat faasien tasapainotiloja. Pelletin pehmenemisen aiheuttaa sulan muodostuminen, joka laukaisee wüstiitin liukenemisen sitä ympäröivään sulaan kuonafaasiin.

Abstract A blast furnace is the dominant process for making iron in the world. Iron ore pellets are commonly used as iron burden materials in a blast furnace, in which iron oxides are reduced to metallic molten iron. While descending, the charge faces various stresses, which affect the gas flows in the shaft and the energy efficiency of the process. Charge material testing on a laboratory scale is of crucial importance in regard to the development of material quality. This doctoral thesis presents a couple of advanced novel experimental methods: a novel camera imaging method to determine the amount of swelling during reduction; a novel reducibility test to determine the reducibility in a solid state under simulated blast furnace conditions; and a novel experimental program for the ARUL reduction-softening test to more accurately simulate blast furnace conditions. Swelling tests under conditions of fixed temperature and gas composition showed that isothermal tests do not give a realistic insight into the material behaviour in a blast furnace. As a result, it is suggested that dynamic gas composition – temperature programmes simulating actual process conditions should be used. Additionally, the test results showed that circulating elements (sulphur and potassium) also affect the pellet volume change during reduction, however no abnormal swelling was observed in any of the swelling experiments. The factors affecting the high-temperature properties of iron burden materials for blast furnace use were evaluated by both the experimental methods and computational thermodynamics. It was shown that none of the studied pellet grades has as good reduction-softening properties as the fluxed sinter because of the differences in the chemistry and macro-porosity. FeO-SiO2-CaO-MgO-Al2O3 system examinations with FactSage was found to be a useful tool for predicting the softening of an iron burden material using the original chemical composition. FactSage computations suggest that the softening properties of an iron burden material can be improved either by decreasing the proportion of SiO2, increasing the proportion of MgO or introducing an appropriate amount of CaO in relation to the proportion of SiO2. / Tiivistelmä Masuuni on merkittävin raakaraudan valmistusprosessi maailmassa. Masuunissa käytetään yleisesti rautamalmipellettejä rautapanosmateriaalina. Masuunissa raudanoksidit pelkistetään metalliseksi rautasulaksi. Vajotessaan panos kohtaa monenlaisia rasitteita, joilla on vaikutusta kuilun kaasuvirtauksiin ja masuuniprosessin energiatehokkuuteen. Panosmateriaalien testaus laboratoriomittakaavassa on merkittävässä roolissa, kun niiden laatua kehitetään. Väitöskirjassa esitetään useita kehittyneitä koemenetelmiä: uusi kamerakuvausmenetelmä, jolla voidaan määrittää turpoaminen pelkistyksen edetessä; uusi pelkistyvyystesti, jolla voidaan määrittää rautapanosmateriaalin pelkistyminen kiinteässä tilassa masuunia jäljittelevissä olosuhteissa; ja uusi koeohjelma, jolla voidaan jäljitellä aiempaa tarkemmin masuuniolosuhteita sulamis-pehmenemiskokeessa. Turpoamistestit vakioiduissa olosuhteissa osoittivat, että isotermiset testit eivät anna realistista kuvaa materiaalin käyttäytymisestä masuunissa. Tämän vuoksi dynaamisia kaasukoostumus–lämpötila-ohjelmia tulisi suosia. Lisäksi tutkimustulokset osoittavat, että myös masuunissa kiertävillä komponenteilla (rikillä ja kaliumilla) on vaikutusta pelletin tilavuuden muutokseen pelkistyksessä. Yhdessäkään turpoamiskokeessa ei kuitenkaan havaittu katastrofaalista turpoamista. Masuunin rautapanosmateriaalien korkealämpötilaominaisuuksiin vaikuttavia tekijöitä arvioitiin sekä kokeellisin menetelmin että termodynaamisin laskelmin. Yhdelläkään tutkitulla pellettilaadulla ei havaittu sintterin veroisia korkealämpötilaominaisuuksia, mikä johtuu eroista kemiallisessa koostumuksessa ja makrohuokoisuudessa. FeO-SiO2-CaO-MgO-Al2O3 systeemitarkastelut rautapanosmateriaalin lähtökoostumuksella todettiin toimivaksi menetelmäksi arvioida panosmateriaalin pehmenemiskäyttäytymistä. FactSage-laskennat antavat ymmärtää, että rautapanosmateriaalin pehmenemisominaisuuksia voidaan parantaa joko vähentämällä SiO2:n osuutta, lisäämällä MgO:n osuutta tai lisäämällä CaO:ta sopiva määrä SiO2:n osuuteen nähden.

An easy-to-use spreadsheet version of a finite difference method for progressive landslide analysis has been developed. The finite difference method was originally developed by Dr. Stig Bernander, earlier adjunct professor at Luleå University of Technology and head of the Design Department of Skanska AB in Gothenburg, Sweden.. The so called Muskrat Falls Project consists in the ongoing construction of a hydroelectric power plant in Churchill River Valley, Labrador, Canada. The site hosting the project includes a land ridge which is supposed to be used as a natural dam and thus be submitted to important water pressures. Yet, previous landslides in the area have shown that a stability analysis is worth to be carried out in order to ensure the safety of the facility. Until now, investigations have only been carried out using the traditional limit equilibrium method and related elastic-plastic theory. For the sake of simplicity, this approach does not take into account deformations outside and inside the sliding body. However, because of the soil features in Churchill River Valley and particularly its ‘deformation softening’ behavior, there is increasing evidence that the conventional analysis is not relevant in this situation. Further, when analyzing the total stability of the ridge, only a horizontal failure surface has been used and not an inclined one, which is very optimistic and rather unrealistic.. In order to provide a more reliable study, a progressive failure analysis has been performed according to the finite difference method of Dr. Stig Bernander. The development of a spreadsheet adapted to this particular problem has allowed getting quickly and easily numerical results for several cases of study and assumptions. For assumed material properties and geometries of failure, the critical load-carrying capacity is below 1000 kN/m whereas a rise of the water level with 21 m will give an increased load of Nq  = 2420 kN/m. This is more than twice of the what the ridge may stand with the assumed properties. The investigation has led to the conclusion that the situation will be risky for many combinations of soil properties if the water level is raised as high as initially planned. The investigation also shows that more material tests are necessary and that stabilization work may be needed to eliminate the risk for a landslide.