Study of Production Drifts Stability and Assessment of Reinforcement Requirements at LKAB Konsuln Test-Mine Levels 436 and 486 Using Geologic Structures Data, and Modelling Software - Dips and Unwedge:  a Part of dp1 Project (Mine Layout and Technology) of the Sustainable Underground Mining (Sum) Project Oludare Joseph Olufe Global population has been on exponential increase over the past half century. The population explosion is driving massive urbanization and infrastructure developments across the globe, which result in huge demand for metals, especially steel. The trend is forecasted to continue to rise steeply in for the next two decades. This is putting enormous strain on metals mining, especially because new surface economic deposits are rare to come by. Therefore, mining is steadily going deeper in many of the mining destinations across the world.     Mining at great depths present unique challenges, particularly regarding stability of excavations at depths. Rock falls, rock burst, excavation collapse are common occurrences associated with deep mining. In regions with high seismicity potentials the frequency and consequences could be very high. Over the past decade ground instability has become a significant challenge confronting mining at LKAB deep mines. There had been incidents that resulted in long term closure of sections of the mines, with resultant adverse economic impacts. More undesirable is loss of live of personnel.     The study was conducted at the Konsuln test mine levels 436 and 486, aimed to investigate the impacts of geologic structures on excavations instability at depths, at the Kiruna iron ore mines, on one hand.  And on the other hand, evaluate the influence of geologic structures on ground reinforcements at the mine. Structural data were collected and analysed using Dips program to define orientation of major structures. The results were used for wedge analysis and excavations stability modelling using Unwedge program. Important rock mechanical parameters were defined based on data provided, and others based on literatures. A design factor of safety of 1.5 was used.     Results from the study established that structures have significant impact on excavations instability at the Konsuln mine. 100% of the production drifts studied has minimum of four wedges formed in its perimeters. Out of this approximately 37% has factor of safety lower than 1.5. Evaluation of reinforcements (shotcrete and rock bolts) implemented in the mine found that approximately 15% of the total wedges formed in the production drifts has factor of safety less that 1.5 after both shotcrete and rock bolt reinforcements had been implement. Also, approximately 5% of the total wedges has apex height longer the rock bolt length.     It was therefore concluded that structurally induced instability is a major contributor to excavations instability at the Kiruna mine. The study approach presented a new methodology to understand and provide robust solution to ground instability problem at the mine.

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Design of braking system for the formula student car. Calculation of basic forces acting in the braking system, including the design of hydraulic circuits. Mechanical analysis of the most important parts of the braking system and pedal assembly. Thermal analysis of the brake discs. Manufacturing and total cost calculation.

Design of braking system for the formula student car. Calculation of basic forces acting in the braking system. Mechanical analysis of the most important parts of the braking system. Manufacturing of brake pedal. Assembly brake components to brake system.

Wood is a widely used construction material that has many advantageous properties, and some drawbacks. These drawbacks are mainly associated with the porous vascular structure of wood that makes it a high water-absorbent material. In addition, wood’s properties alter substantially with respect to the moisture content. Amongst the treatment techniques that limit the water uptake capacity of wood, vacuum-aided impregnation has exhibited promising results. However, little research has explored the effect of key parameters (such as the vacuum pressure) on the effectiveness of the impregnation. This study aims to optimize the performance of SiO2 impregnation of spruce wood under vacuum pressures. The main objective of this research is to overcome wood’s weakness by reducing its water uptake capacity through a vacuum-aided impregnation technique and study its effect on the physico-mechanical properties of wood under dry and saturated conditions. The study was conducted in two parts. In the first part, wood samples underwent impregnation under atmospheric and three vacuum pressures. Density measurements, water uptake tests, microscopy examination, thermogravimetric analysis, and dynamic mechanical analysis were conducted on non-treated and SiO2-treated samples. Quantitative and qualitative analyses demonstrated that SiO2 impregnation performed under -90 kPa was able to effectively enhance the wood’s properties compared to the other conditions. The SiO2 impregnation under high vacuum pressure demonstrated an effective increase in the density of the wood and achieved a significant reduction in the water uptake capacity. The analysis of the wood’s viscoelastic properties revealed that SiO2 impregnation under atmospheric and vacuum conditions triggered two different reinforcing mechanisms: a solid film, causing stick-slip oscillation, and particle diffusion, causing particle-particle and particle-lumen wall friction, respectively. For the second part, characterization methods such as Impact test, DMA, SEM, EDS, Porosity, and SAXS tests were conducted on non-treated and -90 kPa treated spruce wood samples in dry, saturated, and submerged states in order to reveal the synergistic effect of the SiO2 impregnation pressure and water uptake on the wood’s properties. The results showed that high vacuum impregnation pressure has a significant positive reinforcing effect on the wood’s properties. It increased the impact resistance of wood in dry and saturated conditions. A high vacuum impregnation was able to overcome the softening effect of water and caused a significant increase in the Storage modulus by strengthening the wood’s vascular structure, which accordingly increased the wood’s capacity to absorb energy. High vacuum impregnation was also able to counteract the plasticizing effect of water and significantly increased the Loss modulus by increasing the internal friction in the wood with the diffusion of the nanoparticles in the wood’s cell walls and vascular structure. This phenomenon increased the wood's capacity to absorb and dissipate energy under dry and submerged conditions.

New resin-based composites and resin-infiltrated ceramics are used to fabricate computer-aided design (CAD) and computer-aided manufacturing (CAM)-based restorations, although little information is available on the long-term performance of these materials. The aim of this investigation was to determine the effects of storage time (24 h, 90 days, 180 days) on the thermophysical properties of resin-based CAD/CAM materials. Thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used in the study. TGA provided insight into the composition of the resin-based materials and the influence of internal plasticization and water sorption. Resin-based composites showed different decomposition, heat energy and mechanical behavior, which was influenced by storage time in water. Individual materials such as Grandio bloc showed lower influence of water storage while maintaining good mechanical properties.

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No description available.

No description available.

Este trabalho apresenta o estudo de um sistema polimérico bi-componente formado por Poli(Ácido carboxílico)-Poli(Eter-poliol), constituído primariamente de um polímero acrílico polimerizado pelo processo de polimerização em solução aquosa por mecanismo de radicais livres ao qual foi adicionado seqüencialmente, um Poli(Eter-poliol), ambos de baixo peso molecular médio. Tal sistema tem por finalidade atuar como dispersante-ligante em sistema cerâmico à base de caulim CADAM, uma vez que este sistema apresenta propriedades termoplásticas e termorrígidas a diferentes temperaturas. Foram sintetizados 03 protótipos de um sistema polimérico e o critério para escolha teve como base o pH do sistema em sentido generalizado, isto é, compreendendo as diversas fases de preparação dos polímeros e sua aplicação final. É do conhecimento comum que a reação de esterificação entre grupos COOHOH requer catálise ácida para ocorrer, o qual usualmente é realizada em pH abaixo de 4 e, neste ensaio, este pH ácido é devido à presença de ácido para-toluenosulfônico, que atua como catalisador de esterificação. Em tal intervalo de pH, em virtude do ponto isoelétrico do caulim ser comumentemente abaixo de 4, a estabilização da dispersão de caulim por repulsão eletrostática utilizando polímeros sintéticos é improvável de ocorrer, razão pela qual buscou-se mecanismos alternativos para obtenção de uma tal estabilização, entre os quais o mecanismo estérico surge como opção. O sistema polimérico do presente estudo apresenta-se na forma de uma solução aquosa sendo, de fato, uma mistura homogênea de um copolímero de ácido acrílico, N- metiloacrilamida e metacrilato de metoxipolietileno glicol e um poli(eter-poliol). O poli(eter-poliol) e N-metilolacrilamida presentes no sistema polimérico são principais fontes de grupo hidroxila para reação de poliesterificação e formação de ligações cruzadas à temperatura de 150 a 200 °C. No estado termoplástico o sistema polimérico produzido pela mistura poli(ácido carboxílico)-poli(eter-poliol) pode ser utilizado como dispersante de argilas com especial fóco sobre caulim como tratado neste trabalho. A propriedade dispersante pode ser atribuida à presença de grupos carboxílicos e metoxipolietilenoglicol aleatoriamente distribuídos ao longo da cadeia polimérica e, também, ao baixo peso molecular médio. A temperaturas entre 150 a 200 °C, o polímero é reticulado (crosslinked) por reação de poliesterificação, catalisada por ácido, entre grupos carboxila e grupos hidroxila, sendo as hidroxilas provenientes tanto de poliol como de N-metilolacrilamida (NMAM). Assim, do ponto de vista térmico comporta-se como termorrígido, sendo nesta condição insolúvel em água e adequado atuar como ligante na manufatura de materiais cerâmicos. Medidas de mobilidade eletroforética e viscosidade são aplicadas à caracterização de caulim e do sistema polimérico a fim de avaliar a potencialidade de aplicação como dispersante desta argila. Também, as transições dos estados termoplásticos para termorrigidos foram determinadas por análise termogravimétrica (TG) e análise dinâmico mecânica (DMA) nos polímeros isoladamente e depois com medidas de resistência mecânica do sistema caulim/polímero. O sistema apresentou comportamento dispersante em água e ligante após cura. Um sistema polimérico assim sintetizado foi propriamente curado por calor tornando- se, na forma termorrígida, um ligante para peças cerâmicas com propriedades mecânicas de alto desempenho, como resistência a flexão no estado cru (green strenght). / This work presents the study of a polymeric bi-component system made from Poly(carboxylic acid)-Poly(ether-polyol) primarily constituted of an acrylic acid polymerized through the process of aqueous solution polymerization by free radical mechanism, to which a poly(ether-polyol) has been sequentially added, both of them of low average molecular weight. Such a system has the aim to act as dispersing-binding balance on CADAM kaolin targeting to evaluate the applicability potential or the preparation of ceramic bodies as this polymeric system presents thermoplastic and thermosetting properties at different temperatures. Were made the synthesis of 03 polymeric system prototypes which criteria for choice was based on pH of the system at whole sense, that is, regarding the several steps for polymers preparation and its final application. It is knowledge that esterification reaction between COOH-OH groups requires acid catalyst to occur, which usually is done at pH below 4 and, in this work this pH is due to p-toluene sulfonic acid that act as esterification catalyst. In this range of pH, due to the isoeletric point of kaolin to be below 4 the electrostatic stabilization of dispersion is unlikely to occur, from which reason was looked for an alternative mechanism to achieve the dispersion stabilization, among them the steric mechanism arises an option. The polymeric system of this study is the form of an aqueous solution, which actually is a homogeneous blend of a copolymer of acrylic acid, N-Methylolacrylamide Methoxypolyethyleneglycol Methacrylate (MPEGMA) and Poly(ether-polyol). The Poly(etherpolyol) and the N-Methylolacrylamide presents at the polymeric system are the main sources of hydroxyl groups to enhance the polyesterification reaction for further crosslinking at temperatures from 160 to 200 °C. At the thermoplastic state the polymeric system made by Poly(carboxilic acid)poly(ether-polyol) macromolecules may be used as clay dispersant focusing on kaolin for this work. The dispersant property may be attributed to the carboxylic and methoxypolyethyleneglycol group randomly distributed along the polymeric chain backbone and, also to the low average molecular weight. At temperatures between 150 to 200 °C, the polymer is crosslinked by polyesterification reaction catalized by acid between carboxyl groups and hydroxyl groups, in such way that hydroxyls groups comes both from the polyol base polymer and NMethylolacrylamide (NMAM) present at first polymer backbone. Thus, through a thermal standpoint it behaves as thermoset being that, under this condition, water insoluble and adequate to act as binder for manufacturing of ceramic materials. Electrophoretic mobility and viscosity measurements were applied for the characterization of kaolin and the polymeric system targeting to the evaluation its potential application as a dispersant for this clay. Also, the transitions from the thermoplastic to the thermoset state have been determined by thermo-gravimetric analysis (TG) and dynamicmechanical analysis (DMA) for the Poly(carboxylc acid)poly(ether-polyol) polymers alone and further by mechanical resistance measurements for a clay-polymer system. The system has presented both dispersant behavior on aqueous media and binder just afterward cure. A polymeric system thus synthesized was properly cured by heat turning and then, at the thermoset state, become suitable for act as a binder for ceramic bodies with high performance mechanical properties measured as flexural resistance at green strength.