Abstract in English:Abstract The use of rolled hollow sections has been substantially boosted mainly due to the advantages associated with structural behavior and aesthetics, leading to an intense use in Europe, Southeast Asia, North America, Australia, and now, in Brazil due to the wider supply of these profiles. Therefore, it is important to investigate the structural behavior in order to provide an adequate structural design for the civil engineering community. Thus, this paper presents a parametric analysis of a reinforced T-joint focused on NBR 16239 provisions. Two types of reinforcement plates: Collar and Double were investigated. A wide set of numerical models has been defined varying the thickness of the reinforcing plate, chord and brace members and axial loads applied in the brace. The numerical models have been developed using ANSYS 12.0 software considering both geometrical and material non-linearity. Concerning the results, there was a slight gain of resistance when a double plate reinforcement was used, mainly for small displacement, due to large stiffness provided and a linear response up to the serviceability limit. In addition, Von Mises stress distribution confirmed the type A failure with chord yielding beginning at the upper chord surface. Comparing the numerical results with NBR 16239 provisions, an excessive conservatism was noted for this code. In fact, the Brazilian code only takes into account the reinforcement thickness in joint resistance. However, when the results provided by the new proposal where both thicknesses (chord and reinforcement) are considered, a more realistic assessment of the joint capacity is obtained.
Abstract in English:Abstract The Acaiaca Complex (AC) is located in southeastern Minas Gerais state, and comprises felsic, mafic, ultramafic, and aluminous granulites as well as lower grade gneisses and mylonites. The complex is distributed over an area of ca. 36 km by 6 km, surrounded by amphibolite facies gneisses of the Mantiqueira Complex (MC). The discrepancy in the metamorphic grade between both complexes led to the present study aiming to understand the metamorphic history of the AC by means of geothermobarometric calculations and electron microprobe Th-U-Pb monazite dating. Estimates of the metamorphic conditions of the granulites based on conventional geothermobarometry and THERMOCALC resulted in temperatures around 800 ºC and pressures between of 5.0 and 9.9 kbar and a retrometamorphic path characterized by near-isobaric cooling. Part of the granulites was affected by anatexis. The melting of felsic granulites resulted in the generation of pegmatites and two aluminous lithotypes. These are: i) garnet-sillimanite granulite with euhedral plagioclase and cordierite that show straight faces against quartz, and is the crystallization product of an anatectic melt, and ii) garnet-kyanite-cordierite granulite, which is probably the restite of anatexis, as indicated by textures and high magnesium contents. Th-U-Pb monazite geochronology of two granulite samples resulted in a metamorphic age around 2060 Ma, which is similar to the age of the MC registered in the literature. The similar Paleoproterozoic metamorphic ages of both complexes lead to the conclusion that the Acaiaca Complex may be the high grade metamorphic unit geochronologically related to the lower grade Mantiqueira Complex.
Abstract in English:Abstract The Capelinha Formation (Macaúbas Group) consists of a lower quartzitic unit with metamafic intercalations and an upper metapelitic sequence. It occurs in a complex tectono-metamorphic sector of the Araçuaí orogen, where post-collisional collapse-related structures superimposed collisional structures. The garnet-bearing assemblages started crystallization in the collisional deformation stage that formed the main regional foliation around 570 Ma. Garnet porphyroblasts display a well-developed growth zonation of Fe-Mg-Ca-Mn and show, from core to rim, increasing almandine and pyrope contents in contrast with decreasing grossular and spessartine contents. Mineral relations and microstructures provide criteria for local equilibria and a structurally controlled application of geothermobarometers based on cation exchange and net transfer reactions. The P-T values calculated from cores to rims of garnets, aligned along clockwise trends, resulted in increasing temperatures (from 500 ºC up to 620 ºC) under decompression conditions (from 8.0 kbar to 4.5 kbar). The Th-U-Pb dating of homogeneous monazites by electron microprobe revealed a recrystallization period at around 490 - 480 Ma. These ages can be related to the tectono-thermal event associated with the gravitational collapse, constraining the youngest time limit for metamorphic processes in the Araçuaí orogen.
Abstract in English:Abstract The natural ventilation in a building performs a fundamental role in users' welfare and health, when used as a bioclimatic and architectural strategy, it can provide brighter projects. Increasing the indoor air speed ventilation has an important performance maintaining indoor air quality, contributing to thermal interactions between human body and environment, which can significantly reduce the building's energy cost. In this study, a numerical research of natural convection in single-sided and cross ventilation is developed using the finite volume method, taking account the internal heat sources influence. The numerical model is used to determine the effects of wind and thermal forces combined by analyzing the stream functions and temperature distribution within an office. The turbulence model is the two differential equations for the low Reynolds number. The building's internal heat sources influence is analyzed herein. The results show that the single-sided ventilation presents excellent conformity with the results obtained in literature. The influence of the internal heat source is considered and it has been observed that the best source position is near to the air exit for both single-sided ventilation and cross ventilation.
Abstract in English:Abstract The evaluation of material fracture mechanic properties has had an increasing need, especially in the oil and gas industries. This scenario requires quality assurance of fracture toughness tests. This article describes the activities carried out when implementing the Quality Management System (QMS) for the fracture toughness tests at the Physical Metallurgy Laboratory (LAMEF) in the Federal University of Rio Grande do Sul (UFRGS), Brazil, in order to achieve the management and technical requirements of ISO/IEC 17025. Since LAMEF was previously accredited in performing other tests, most of the adequacy was related to the technical requirements of the ISO/IEC 17025 standard. After performing the required adjustments and after an external audit, the Brazilian Institute of Metrology, Quality and Technology (Inmetro) accredited LAMEF to the fracture toughness tests. The accreditation of these tests is unprecedented in Brazil, and we expect this work to encourage other Brazilian and world laboratories to seek the implementation and accreditation of QMS for fracture mechanics tests.
Abstract in English:Abstract Crystallographic textures of the austenitic low-density Fe-30.5Mn-8.0Al-1.2C (8Al) and Fe-30.5Mn-2.1Al-1.2C (2Al) (wt.%) steels were examined during cold rolling by means of electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). Random oriented grains orient towards Goss- and brass-components along the α-fiber as the strain increased, with activation of slip, mechanical twinning, and shear banding, for both steels. S- and copper-orientations were also observed in the 8Al steel at 50% reduction. The route of Cu-CuT-Goss-brass texture evolution was found in the 2Al alloy. Cu, Goss, and brass textures occur as a dominant texture in the deformed 8Al alloy. Copper-type texture accompanied with slip at low reduction (20%), as well as Cu-type shear bands, and shear banding inside Goss-oriented grains at higher reduction (50%), were observed in the 8Al steel. It is suggested that this copper-type rolling texture may be attributed to the Al addition, which contributes to its low twinning activity compared to that in the 2Al alloy. Cu-CuT-brass f.c.c. rolling texture transition to form the Brass-type texture was observed at higher reduction in the 2Al alloy with strong similarity to that found in other Fe-Mn-C system TWIP steels.
Abstract in English:Abstract The paper aims to outline the causes that affected a rare earth metal producer Molycorp Silmet's internationalization based on case study evidence. Moreover, based on statistical analysis, it aims to study how its internationalization and financial performance were interconnected. It concludes that 1) its export fluctuations mostly resulted from external factors and that despite such fluctuations, the firm's financial health was mostly good, 2) high concentration on a single target market can lower profitability, 3) fluctuations in target market shares can increase or decrease a firm's profitability, but they are not interconnected with its bankruptcy probability.
Abstract in English:Abstract The construction of block models with an estimation of grades in situ is a common practice throughout resource evaluation. However, this information is not enough to understand the behavior of the ore in the beneficiation process. Geometallurgy proposes the addition of the ore´s metallurgical behavior in the block model, making it more dependable and adhering when it comes to production capacity, which generates financial earnings and brings risks down. Mass recovery is an important metallurgical variable for economic and mine planning. This is often underused, due to the lack of data, making it hard to use in the planning process. In order to achieve better use of the data available, the multiple regression analysis technique was used so as to develop a statistic model that would relate the mass recovery with the in situ grades, allowing that deposit regions with no available metallurgical information have an estimation of this variable's values.
Abstract in English:Abstract This article objectifies the implementation of a conveyor belt in an iron ore mine. The mine operational costs of the company Vale S.A. have a tendency to increase in coming years. This increase is related to the rising price of labor, fuel, tires, maintenance costs and large transport distances. Meanwhile, environmental impacts also need to be reduced. The case study of the Fabrica mine operated by VALE in the city of Congonhas, in Minas Gerais State of Brazil, was chosen aiming for a comparative study between the employment of big trucks and the deployment of conveyor belts. The decision for the best alternative would be made by an economic analysis of the incremental cash flow. After the economic evaluation of the project, economic and environmental gains were expected for the alternative of conveyor belt deployment.
Abstract in English:Abstract Beneficiation of manganese ores has been conducted around the world by circuits composed basically of crushing, screening and spiral classifier. Therefore, solely the coarse size fractions (and commonly the richest) are actually recovered: "lump" (-75+9mm) and "sinter feed" (-9+0.15mm). In the industrial plant which processes the ore from the Azul Mine-PA, the overflow of the spiral classifier (- 0.15mm) is disposed of in a tailings dam because it bears a low Mn content (<10%) and high kaolinite content (70%). This paper reports the findings of a process development conducted on laboratory scale with the aim of concentrating Mn-bearing minerals from the tailings of the Azul Mine-PA (7% of Mn and 70% of kaolinite). The process is composed of desliming (-10µm), followed by reverse cationic flotation of kaolinite (rougher, scavenger) at pH~5. Results indicate that the reverse cationic flotation in the acid medium, when utilizing amide amine as collector and in the presence of a silicate activator and a dispersing agent could be a possible route for the concentration of tailings that had previously been deslimed at 10µm. The results yielded a mass recovery of 18%, a metallurgical recovery of 50% and a 32% Mn concentrate which may be mixed with current high grade products, increasing the overall recovery of the plant.
Abstract in English:Abstract The Bond method for ball mil designing has been used for 60 years. Based on the Work Index test, such method is applied mostly in traditional circuit configuration, which includes multi-staged crushing, followed by rod and ball milling. On the other hand, simulation is a widespread and used technique for comminution, classification modeling, and simulation. Even though both methods are complementary, there is no effective integration between them. This work shows a technique designed to integrate both energy and modeling approaches for estimating and improving ball mill grinding performance. The work is based on industrial data survey results, as well as on laboratory testing, the latter developed specifically for such a purpose. The technique was validated under an industrial environment for assessing the obtained results.
Abstract in English:Abstract This work adds the Activity-Based Costing Approach in mining operations with a product mix. After analyzing and collecting data from an aggregate mine located in Brazil, a cost model was built, and from that, a cost management and analysis methodology of a mine in operation is created. This work has the innovation advantages of using ABC as a tool for planning the operation of the mine, identifying the more profitable products. At the end, it is concluded that the creation of a cost model to be used in the operation of mining is a rewarding investment as it shows the profitable and unprofitable products.
Abstract in English:Abstract Recently, the Brazilian media reported the withdrawal of the rate on profit from mining of coal and iron ore by the government of Australia. In Australia this rate was created in 2012 to finance social programs. However, due to the drop in the value of mineral commodities, the government has reversed this trend and seeks to quash the law that created such a rate, while keeping its social program financial support. One can observe the opposite in Brazil, where the states of Minas Gerais, Pará, Amapá and Mato Grosso do Sul, created the Rate for Controlling, Monitoring and Supervision of Exploration and Mining Activities of Mineral Resources (TFRM). These states' rates have been grounds for numerous political, economic, administrative and legal discussions. This paper presents an analysis of state laws that created the TFRM, examines the ways taken by mining companies to question the constitutionality of these laws and concludes that the levy of TFRM breaks the principle of equality, penalizes mining, violates the precept contained in article 152 the Federal Constitution of 1988 and helps reduce the competitiveness of Brazilian mining.