Materials Science Forum Vol. 805

Abstract: Tantalum has characteristics such as excellent ductility, high corrosion resistance, high mechanical strength at high temperatures and high resistance to etching of acids and bases. Its high ductility allows the realization of large reductions without the need for intermediate heat treatment. A process for the production of tantalum wire is drawing. However, when using this process, the high ductility of the tantalum (Ta) metal causes a retention/accumulation of the Ta in the spinneret. Therefore, to be drawn is necessary that the tantalum is encapsulated in a copper tube. In this work was produced a Ta wire by means of rotary forging and drawing process. In the drawing process of the tantalum encapsulated in copper tube, was the appearance of striation on the surface of tantalum, when applied to an area reduction (AR) of approximately 22%. This fact is possibly related to the different sliding systems with consequent formation of non-hydrostatic stress fields at the interface Cu / Ta. After an area reduction (AR) of 94% the Cu was removed from the surface of the wire, through chemical etching, and this wire was drawn up to 0.43mm without retention/accumulation of the Ta in the spinneret.

Abstract: The refractory metals and their alloys show excellent mechanical behavior in high temperatures and high resistance to corrosion and to wear and good thermal conductivity. The metals that constitute this group are, traditionally, tantalum, molybdenum, tungsten and niobium. Niobium (Nb) is a metal with 2468°C melting point, density 8.57 g/cm³ and CCC crystalline structure, is characterized by its excellent ductility and reasonable mechanical resistance in high temperatures. Due to these properties, o Nb is applied in chemical, nuclear and electrical industry and in the superconductor wire production. One of the processes used in niobium plastic deformation is the swage that consists in one direct deformation process, which can be done at hot or cold temperature, used to modify the transversal section area of bars, tubes and wires. The microstructure evolution during a plastic deformation is very important in the relation of deformation mechanism, mechanical property and texture formation. The aim of this work is to evaluate the microstructural and mechanical behavior of metal cold rotary forging – swage using the techniques of Scanning Electronic Microscopic – SEM e microhardeness Vickers. Metallographic analysis of the microstructure of Nb after deformation of 96.4%, shows a distorted shape called "ripple". The Vickers microhardeness results indicate that there is a gradual increase in the microhardness of Nb up to 80% reduction in area taking place stabilization after this value. It may be noted that in both directions, the center of sample had higher hardness values

Abstract: In today's industry, production processes evolve every day, together with the development of new materials and geometries for tools and machines more accurate and efficient. These new technologies allow more flexible processes, such as replacement of the grinding process by turning of hardened materials. This change brings significant reductions in costs of tooling, setup time and machining.This work is a study of the conditions for turning aerospace alloy - Bronze Aluminum (UNS 63020)-hardened and tempered with a hardness of 35 HRC with carbide tools with positive and negative geometry.We analyzed the surface roughness of the specimen and as a criterion for end of life of the cutting tool was used to flank wear, crater wear, chip on the tool and/or the breach thereof.All the cutting parameters, when in their highest levels, do not contribute significantly to the reduction in tool life, while the surface roughness for the increase in the feed (f) and the cutting speed (vc) showed a greater influence on surface finish of the piece.

Abstract: In machining processes the chip is considered the disposal of no interest and so little analysis of the morphology observed as the types and forms submitted. The machining does not equal the composition of the physical properties of metal forming, it involves forces or active and inactive stocks. The combination of parameters, conditions and variables of the machining is a means of speculating and trying to explain the phenomena. Such actions reflect directly on the wear of tooling, and structural integrity. The experimental study of machining is of essential importance for the theory of plasticity can not explain satisfactorily the observed phenomena. The speed and the deformations are very large in the machining process, compared with those treated in this theory. This material may reveal why this chip segmented nature which are characterized by continuous large deformation in narrow bands between segments with little or no strain in their interiors. This is a very different from the continuous chip. With the aid of a tool in the expanding area of technology and scientific processing and analysis of images could provide a better analysis of the chips. The goal of this study was to relate the microstructure of the chips of superalloy Aluminum Bronze (C 63020) with milling parameters used in the process of turning on a CNC lathe Nardini - LOGIC 175, in order to analyze the behavior of even through a mechanical process.

Abstract: Our ability to predict clouds and precipitation at the daily, weekly and monthly scales is very limited partly due to the limited computing resources and realistic physical model representations Giorgi et al. (1991).

Abstract: Conventional comminution (crushing and grinding) uses compressive forces to initiate and propagate cracks throughout the rock mass, yet the material actually breaks under tension since this strength characteristic is about 10 percent of the compressive strength. Converting a compressive force into a tensile one is inefficient - of the order of 1 to 2 percent. On the other hand, blasting shows energy efficiencies of the order of 10 to 20%. Part of this difference is due to forces being applied directly in tension (from the inside-out), but also because the velocity of impact is orders of magnitude higher (10,000 m·s^-1 versus 10 m·s^-1), i.e., the rate of energy input is very high (micro-seconds vs. seconds in conventional comminution). This paper reports on studies that show how the energy efficiency of comminution can be enhanced by high-velocity impact. This research project has carried out investigations into the relationship between energy efficiency with energy input level and impact velocity during rock fragmentation by metal projectiles. The project has also examined rock-on-rock breakage. Samples of magnetite particles of varying weights and size distributions were impacted by a projectile at velocities from 50 m·s^-1 to 400 m·s^-1. The specific surface area of the sample was measured before and after each experiment, and the energy recovered as new surface energy (energy efficiency) was calculated. The results indicate that energy efficiency increases to about 5% as impact velocity enters the range from 200 to 300 m·s^-1. This efficiency is over 3 times that observed in conventional comminution. Above this velocity, the efficiency begins to fall off although significant comminution at higher than normal efficiencies are still attained. The improvement results from both increased rate of energy input and increased impact velocity. Rock-on-rock impacts using a glass projectile shows that the energy of new surface generation is distributed between the projectile and the sample to a combined level similar to that of the steel-on-rock tests in which all the useful energy is retained within the sample. Suggestions are given as to how this energy improvement could be scaled-up into an impact crusher.

Abstract: The world is going through a new-millennium rush in precious metals, especially gold. The great increase in gold price in the last years, probably due to a shift towards safe investments in a period of crisis in the global economy, created a rapid increase in gold production. The faster response to this shift in production came from Artisanal (ASM) and Small-scale (SSM) mining units in remote locations of the world, and Brazil is one of the main countries that has ASM and SSM on its territory. The present paper draws some definitions of Small-Scale Mining and Artisanal Mining, based on its productivity and its actual social and environmental implications, and of their sustainability. The analysis of production data of Small Scale and Large Scale Mining on global scale and on Brazilian scale shows the high potential of SSM in dealing with lower mineral grades and market fluctuations, due to its high flexibility. A general growth of the role of SSM in precious metals production in the next decades is foreseen. An elaboration on world ASM data led to a clear correlation between efficiency in production and an index of human development; this result is shown and discussed. Based on the potential of SSM to attend to the mineral market needs, efficiency in productivity is finally proposed as the main path to turn an ASM unit into a sustainable and profitable Small-Scale industrial extractive unit.

Abstract: Increased public awareness of the threats posed by global warming has led to greater concern over the impact of anthropogenic carbon emissions on the global climate associated with the level of carbon dioxide (CO₂) in the atmosphere. Hence, without radical market, technological, and cultural changes, the CO₂ concentrations are expected to rise to unbearable levels within just few decades ahead. The production of cement is estimated to be responsible for approximately 5% of the global carbon dioxide emissions. Consequently, aiming for creating a more sustainable world, engineers and scientists must develop and put into use greener building materials that may revolutionize the entire construction industry. This study presents an innovative product for settlement of ceramic tiles as a potential alternative for replacing the conventional cement based mortar in some specific building applications. Essentially, the novel system is based on a double face polymer-adhesive sheet (“cement-free product”). Thus, the main goal was to evaluate the performance and estimate the durability of the developed system. Pull-off tests were conducted in order to compare this new system to the traditional one, with polymer modified mortar, under different procedures and conditions of cure. In addition, both systems were modeled using Finite Element Method (FEM) to obtain the stresses at the interface between ceramic-tile and adhesive. Based on the results, the recommended limits of bond strength for the innovative “cement-free product” of ceramic tile installation could be lower than those specifications used for the equivalent mortar systems. Therefore, these results give some preliminary evidence that by using the new “cement-free” product for ceramic-tile installation may lead to some increase in the productivity and, more important, in the sustainability of a relevant sector of the construction industry.

Abstract: Petroleum engineering is advancing to exploit deeper and more unstable formations. Therefore, the knowledge of how the reservoir behaves with production has to increase significantly. That is why in the study of reservoir engineering simulation is necessary: to understand how the reservoir behaves without actually having a producing well to perform monitoring on. Brazil, as one of the leading entrepreneurs in non-traditional wells, needs engineers who have the know-how in reservoir engineering. A fluid flow simulator has been developed with an input of the geological information of the formation in which the reservoir is, the desired production, how many and what types of wells (production or injection) are to be installed and how long will be the horizon of study. The simulator is designed to solve the derived multi-linear system of differential equations thru numerical analysis. The output is point-to-point graphics of pressure, fluid flow and loss of pressure due to production. These outputs have direct application for academic purposes, showing to first-timers what is the optimal project of production for a reservoir, where the wells should be located to give maximum production with minimum effect to internal pressure, this way increasing the lifespan of the reservoir itself.

Abstract: Modern mining activities are very intense in capital use, highly mechanized and as a consequence, present high operational costs. In this sense the appeal for managing operational variables adequately is very attractive since these have a huge impact in the overall costs. Reportedly, one of the most expensive mining activities is the transportation of in situ material to its destination. In this regard, the correct management of the important operational variables coupled with the experience gathered in mining operations, allowed the development of a computer system aimed at helping to achieve these management objectives. This paper describes the relation between measurable variables and economic parameters obtained in one important large scale Brazilian mine and how they interact and relate to each other in order to facilitate the decision making process.