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By Fernando Andrade Amorim

O processo de micro soldagem se mostra eficiente para a união de Ligas com Memória de Forma (LMF) do sistema NiTi devido a alta precisão e localização do calor, diminuindo os tamanhos da zona fundida (ZF) e da zona termicamente afetada (ZTA), promovendo melhorias nas propriedades mecânicas destes tipos de juntas. Este estudo teve como objetivo geral determinar as variações das propriedades termomecânicas em juntas soldadas de fios de NiTi. Para o trabalho, fios superelásticos de uma LMF NiTi (ASTM F2063) com 0,9 mm de diâmetro, foram divididos em dois grupos: (a) fios sem tratamento térmico (NiTiA) e (b) fios com tratamento térmico a 400°C durante 20 minutos (NiTi400). Em seguida estes fios foram soldados pelo processo TIG, utilizando a microsoldadora Micromelt (EDG Equipamentos e Controles). A caracterização termomecânica dos fios íntegros e microsoldados foi realizada utilizando ensaios de calorimetria diferencial de varredura (DSC), análise dinâmico-mecânica (DMA), ensaios de tração uniaxial, microscopia óptica (MO), microscopia eletrônica de varredura (MEV) e microindentação Vickers. Os resultados mostraram a eficiência do processo TIG ao soldar os fios NiTi de ambos os grupos. As juntas soldadas apresentaram propriedades de superelasticidade semelhante aos fios íntegros e a análise da fratura dos fios com solda mostra características dúcteis.

Aug 7, 2018

By D. Simon

This paper studies the effect of binder type and content on the early age development of cemented paste backfill (CPB). The early age development of the mixtures is analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). These tests show that the early age development of CPB is sensitive to changes in the paste composition. The properties of the CPB depend on the cement content and hydration time. The quantity of hydration products increases with hydration time for all of the mixtures containing cement. However, the high cement content pastes (at least 50% PC) exhibit complete coverage of the PC grains and mine tailings by C-S-H, while the low cement content paste shows scattered coverage of the PC grains and mine tailings and a higher void ratio.

May 1, 2007

By L. Ozdemir, M. Cigla

This paper presents and discusses some of the computer models developed and currently used at the Earth Mechanics Institute (EMI) of the Colorado School of Mines (CSM). These include the performance models for full and partial face machines. Examples of input and output of these models will be illustrated for typical mining operations by using machines such as Tunnel Boring Machines (TBM), Continuous Miners (CM), Marietta borer miners and longwall drum shearers. The general approach to modeling and the available models are discussed and some examples of these models are presented. The comparison between the estimated and achieved performance, as well as the degree of improvement in the performance due to balancing and modification in cutterhead design are also discussed.

Jan 1, 2000

By C. J. Wilhelm

Brine produced from subsurface formations may be employed successfully instead of fresh water as a flooding, medium in the secondary recovery of oil. The feasibility of this substitution has been proved in the shallow "shoestring" area of eastern Kansas and northeastern Oklahoma, where the supply of fresh water often is limited. In this procedure all brine produced with the oil is returned to the formation and thus is prevented from contaminating streams and fresh-water supplies. This report includes a detailed description of a "flood project" in eastern Kansas studied by the Bureau of Mines. In an attempt to determine whether brine, when handled properly, can be used as effectively as fresh water in flooding oil from partly depleted, formations, an analysis was made of all .own conditions that influence flooding.

Jan 1, 1941

By Donald J. Olson

The North 27th St. ISS Extension tunnel will, under present plans, be the last constructed section of Milwaukee Metropolitan Sewerage District?s (MMSD?s) existing deep tunnel system. The 6.5 m (21 ft) finished diameter tunnel is approximately 3,260 m (10,590 ft) long and is located in NE Milwaukee County. When disputes over the pro-cesses to be used in owner-directed pre-excavation grouting in rock threatened the completion date stipulated between MMSD and the State of Wisconsin, the MMSD and J.F. Shea, the contractor, entered into a unique agreement. Shea accepted responsibility for all shaft and tunnel grouting and water control during the project in exchange for settlement of claims related to grout quantities and perceived delays. This significantly reduced risk for the MMSD and helped ensure the stipulated completion of the project.

By J. D. Doll

MSHA has promulgated a rule to limit the exposure of underground metal/nonmetal miners to diesel particulate matter (DPM). In May 2008, the final personal exposure limit will be lowered to 160 µg/m3 total carbon. To comply with this rule, mine operators are implementing a variety of control technologies. In this study two types of control technologies (ventilation and cabs) which are being implemented in limestone mines were investigated. Two stone mines in this study use large diameter propeller fans for main mine ventilation and direct the air to the faces using auxiliary fans, stoppings, and long pillars while bypassing the old mine workings. NIOSH measured for sub-micrometer elemental carbon (EC) using SKC DPM cassettes (analyzed using NIOSH 5040) and a near real time instrument. With the present ventilation and the number and type of vehicles used, the concentration of EC from DPM at the working areas was at or below 400 µg/m3 for both mines and about 166 µg/m3 and 251 µg/m3 at the returns. The real time data showed that the ventilation was reaching the working areas and effectively diluting the DPM. Environmental cabs were also used to reduce DPM exposures in three underground limestone mines. Using NIOSH method 5040 and near real time EC instrumentation, NIOSH sampled inside and outside of a loader cab at one of these limestone mines to determine the effectiveness of the cab. The cab was found to be over 90% effective in removing DPM as long as the cab system was properly maintained, and doors and windows were closed.

Jan 1, 2009

By J. Böhlke, B. Friedrich, E. Hecker

The legislation for the disposal of heavy metals contaminated substances is still going to be tightened up in the future. The main criteria for the utilization or deposition of these residues are the content and the water solubility of these metals. Through this, the use of slags from the lead-and zinc-industry in road building may become limited or even not possible at all. From an economic point of view this would lead to Pb/Zn losses and costs for safe dumping. This paper investigates the feeding of the reducing agent via hollow electrode DC smelting and the yield of metal reduction. After carrying out thermodynamic calculations, the process window conditions for electric-arc furnace tests were determined. Doing this, the zinc could be reduced, evaporated and recovered as an oxidic intermediate product flue dust, while the lead was present either in flue dust or in metallic form. The zinc content in the final slag could be reduced by up to 90%. The slag product has undergone an eluation test which allows it to be used as building materials. Keywords: zinc reduction, lead reduction, hollow electrode, slag treatment, electric arc furnace

By D. M. Wyslouzil

"Micron or sub-micron size gold inclusions in sulphide minerals cannot be extracted by conventional cyanidation. The gold surfaces must first be exposed by decomposition of the sulphides. As an alternative to roasting, pressure oxidation was found to be a most satisfactory method to decompose the sulphides and expose the gold particles. For cyanidation the pressure oxidation pulp has to be neutralized and stabilized with lime. It was found that thiourea can extract the gold directly from the pressure oxidation pulp without pH adjustment and oxidant addition. The main obstacles against the common use of thiourea are circumvented by a recently described control method of the emf during leaching.INTRODUCTION Amalgamation and cyanidation are the most conventional processes for gold extraction. The prerequisite for gold extraction is the possibility of gold surface to be contacted by mercury or by the cyanide solution. Encapsulated gold has little chance of contact and this leads to poor extractions.The reasons why a gold ore may be refractory are: micron or sub-micron size gold particles included in the sulphide minerals, such as pyrite and arsenopyrite; presence of and association with antimony, arsenic, tellurium and carbonaceous minerals. Some alternative processes, such as double oxidation(1,2), pretreatment with lime , H202, chlorine and Caro's acid, roasting and thiourea leach, have solved some of the problems of ""refractory"", but the sub-micron gold in sulphide minerals still shows little response. Roasting and the cyanidation of the calcine was one of the most successful approaches for this type of gold ore.There are two disadvantages to the roasting process: (1) the generation of sulphur, arsenic, antimony and mercury containing gases is undesirable and the control is extremely expensive; (2) gold particles might be fused in the roasted product and the oxidized base metals in the calcine might reduce the cyanidation efficiency. In recent years the pressure oxidation process has been considered as one of the more effective and satisfactory methods to decompose the sulphide minerals and expose the gold surface to the cyanide leach solution. The pollution problem could be better controlled and the gold extraction is more amenable."

Jan 1, 1985

By Kenji Koga

In order to derive the population distribution of gold nanoparticle morphologies as a function of size, highresolution electron microscopic (HREM) observations and structural analyses were done for over 4000 particles (3-18 nm) grown by an inert gas aggregation (IGA) source using helium. To obtain structural features threedimensionally and not to skip high-contrast images, twenty photos were taken for each particle by changing tilting angle of a specimen holder in combination with the through-focus procedure. For the reliable structural determinations, HREM images and their tilting sequences were directly compared with multislice-simulation results for icosahedral, decahedral and face-centered cubic morphologies, and finally the population distribution of each morphology was obtained as a function of size. In the present sample, icosahedral particles were dominantly populated over the whole observed size range and decahedral particles with non-spherical truncated bi-pyramid shape were secondly dominant. Even though a large number of sampling has been done, few crystalline particles were observed.

Oct 1, 2003

By A. S. Macfarlane

The introduction of new technology into mining operations is seen as a strategic necessity by many mining companies, in order to improve safety and to improve operational effectiveness. Many attempts have been made in recent years to introduce new technologies into mining operations in southern Africa. Amongst these are noteworthy successes, as well as some disappointing failures. Often, the reason for failure does not lie with the technology itself, but with the work system into which the technology is introduced. Such failures may come with a significant opportunity cost, and have a detrimental effect on future development, simply because the system has not been adequately engineered, and the risks have not been adequately assessed and managed. This paper examines the reasons for such failures, and proposes a methodology to be followed to ensure successful and sustainable implementation of new technologies, such as to reduce technical and financial risk to the company, and to energize the workforce into ensuring the initial objectives of the project are met. The paper also focuses on the application of appropriate technology, and the development of technological applications which are commensurate with the level of development of the work environment into which it is introduced. The paper therefore focuses on the application of risk management, change management, systems engineering and feasibility analysis as being key elements of a successful and holistic technology implementation programme.

Jan 1, 2001

By C. J. Wilhelm

Brine produced from subsurface formations may be employed successfully instead of fresh water as a flooding, medium in the secondary recovery of oil. The feasibility of this substitution has been proved in the shallow "shoestring" area of eastern Kansas and northeastern Oklahoma, where the supply of fresh water often is limited. In this procedure all brine produced with the oil is returned to the formation and thus is prevented from contaminating streams and fresh-water supplies. This report includes a detailed description of a "flood project" in eastern Kansas studied by the Bureau of Mines. In an attempt to determine whether brine, when handled properly, can be used as effectively as fresh water in flooding oil from partly depleted formations, an analysis was made of all known conditions that influence flooding.

Jan 1, 1941

By J. D. Bittner

The ST separator utilizes electrical charge differences between materials produced by surface contact or triboelectric charging. When two materials are in contact, material with a higher affinity for electrons gains electrons and thus charges negative, while material with lower electron affinity charges positive. This contact exchange of charge is universally observed for all materials, at times causing electrostatic nuisances that are a problem in some industries. Electron affinity is dependent on the chemical composition of the particle surface and will result in substantial differential charging of materials in a mixture of discrete particles of different composition. In the ST separator (Figures 1 and 2), material is fed into the thin gap 0.9 ? 1.5 cm (0.35 -0.6 in.) between two parallel planar electrodes. The particles are triboelectrically charged by inter-particle contact. For example, in the case of coal combustion fly ash, a mixture of carbon particles and mineral particles, the positively charged carbon and the negatively charged mineral are attracted to opposite electrodes. The particles are then swept up by a continuous moving open-mesh belt and conveyed in opposite directions. The belt moves the particles adjacent to each electrode toward opposite ends of the separator. The electric field need only move the particles a tiny fraction of a centimeter to move a particle from a left-moving to a right-moving stream. The counter current flow of the separating particles and continual triboelectric charging by carbon-mineral collisions provides for a multi-stage separation and results in excellent purity and recovery in a single-pass unit. The high belt speed also enables very high throughputs, up to 40 tonnes per hour on a single separator. By controlling various process parameters, such as belt speed, feed point, electrode gap and feed rate, the ST process produces low carbon fly ash at carbon contents of 2 % ± 0.5% from feed fly ashes ranging in carbon from 4% to over 30%.

Feb 27, 2013

By M Lemieux, R Mason

The SABREX blast modeling program was introduced to I.O.C.C.'s Carol Lake Iron Ore Project in December 1987. As part of CIL's Technical Services, SABREX was used to implement an optimization program designed to analyze and introduce various grades of MAGNAFRAC at a constant pattern while maintaining acceptable blast results.

Jan 1, 1989

By John C. Ferm

This report contains a summary of Phase I and complete results of Phase II portions of a study of geologic factors associated with roof falls in mines on the Pocahontas #3 coal seam in southern West Virginia and southwestern Virginia. Principal objectives of Phase I was the selection of five mines that best portrayed the spectrum of roof and mining conditions and Phase II consisted of a measurement and documentation program for each of the five mines. The documentation measurement program included reconnaissance mapping, detailed mapping, joint measurements and coring roof rock. 1.2 PHASE I RESULTS The results of Phase I consisted of the selection of the following five mines for detailed study: Virginia Pocahontas #3 (Island Creek Coal Company), Bishop (Consolidation Coal Company), Shannon Branch (Allied Chemical Company), Keystone II (Eastern Associated Coal Company) and Macalpine-East Gulf (Westmorelenad Coal Company). In addition, Phase I results, which were based on questionnaire data, indicated that the kind of rock in the roof --gray sandstone, crystallized sandstone, laminated sandstone and shale, grey shale, slickensided shale, and rider seams could be associated with good and bad top areas. Also presence of vertical separations, bolt length, entry and cross-cut width, length and torque on bolts and depth of overburden seemed to be related factors. These data provided a focus for the Phase II measurement program.

Jan 1, 1975

By André C. Zingano

The coal pillars in room-and-pillar mining method are subjected to vertical stress due to overburden rock mass and horizontal stress relieve due to entries excavation around them. Some coal mining companies are applying rock bolts and steel straps to improve the pillar strength, consequently to reducing the pillar size and increasing coal recovery. This kind of approach deserves some discussion, whether it is pillar reinforcement or just rib support. The efficiency of pillar reinforcement (or rib support) is directly related to the initial load capacity of coal pillar, the type of excavation, and the width to high ratio of the pillar. The objective of this paper is to understand the mechanism of pillar reinforcement (or rib support) using rock bolts and steel straps on pillar ribs. Numerical simulation taking into account the relations listed above. The results showed that the increase of coal pillar strength is very short, and there is no influence on improvement of load capacity of pillar. However, the rib support avoids block falling, rib failure, and displacement, reducing the pillar failure propagation into the pillar center. Keywords: coal, pillar reinforcement, room and pillar.

Jan 1, 2006

By Robert B. Sosman

THE chance that a Howe Memorial Lecturer will be able to refer back to a personal contact with the distinguished metallurgist for whom this lectureship is named grows steadily smaller. I did not have the pleasure of his personal acquaintance, but I did receive from him in 1916, quite unexpectedly, a letter commenting on a paper that I had recently published27 on "Types of Prismatic Structure in Igneous Rocks." The paper was written for geologists and petrologists, but it had an application, naturally, to the crystallization of iron and steel in a mold. The letter impressed me at the time, and still does, with the breadth of Professor Howe's interests and his perseverance in keeping up with the progress of any branch of knowledge that had metallurgical connotations. SCOPE OF THE LECTURE During several years preceding the date mentioned I had worked in collaboration with Arthur L. Day and E. T. Allen8 at the Geophysical Laboratory, Carnegie Institution of Washington, on the temperature scale as defined by the nitrogen thermometer at high temperatures. Later (1928-1947) I had the opportunity of helping to apply this experience to the pyrometric problems of the steel industry. Because of the range of its temperatures, the multiplicity of the methods used, and the variety of its purposes, pyrometry in the open-hearth process has always offered a fertile field for both research and development. I am therefore devoting an hour to the subject of temperatures in the basic open-hearth furnace, the furnace that makes most of our steel in the United States. I would direct your attention particularly to the choice of the first two words in the title of the Lecture. One sometimes hears or reads of the "temperature of such-and-such a furnace," as if it were a single, measurable, characteristic quantity. I need hardly emphasize to any one who has ever operated a furnace or a kiln that "temperature of the furnace" is a meaningless phrase. Even if we confine our attention to the space enclosed by the roof, walls, and hearth of an open-hearth furnace, it is doubtful whether any such space has ever been so uniform in temperature that the phrase would have a meaning. In any furnace, there are many different temperatures, capable of being measured at many different places, and actually being measured for several different purposes. These pyrometric purposes, methods, and results, if given in detail, would expand this lecture into a book on the basic open-hearth process. I must therefore confine myself to a statement of the range of temperatures as they have been observed in various parts of the furnace, indicating in a general way why they are measured, and mentioning the methods that are available without attempting to describe these

Jan 1, 1948

By F. Kavicka

An original application of ANSYS simulated the forming of the temperature field of a massive casting from ductile cast-iron during the application various methods of its cooling using chills. The numerical model managed to optimize more than one method of cooling but, in addition to that, provided serious results for the successive model of structural and chemical heterogeneity, and so it also contributes to influencing the pouring structure. The file containing the acquired results from both models brings new and, simultaneously, remarkable findings of causal relationships between the structural and chemical heterogeneity and the local solidification time in any point of the casting. The determined relations therefore enable the prediction of the face density of the spheroids of graphite in dependence on the local solidification time. The calculated temperature field of 500x500x1000 mm casting of ductile cast-iron with various methods of cooling has successfully been compared with temperatures obtained experimentally. Acknowledgments. This analysis was conducted using a program devised within the framework of the GA CR projects (No.106/04/1334, No. 106/04/1006 and No. 106/04/094), of the COSTAPOMAT-OC526.10, MPO/FI-IM/021, EUREKA No.2716 COOP and KONTAKT 14/ 2005/06.

Jan 1, 2006

By B. J. Sauer

Variable frequency drives (VFD’s), or adjustable frequency controls (AFC’s) as they are more precisely identified, have been available to the mining industry for over 20 years. However, in recent years as the push to cut production costs has become ever so crucial, AFC usage has become more widespread. This paper seeks to provide professionals in mineral processing plant design and operation with an introduction to AFC’s, insight as to why AFC control for AC induction motors can be advantageous, and specification and design considerations.

Jan 1, 2002

By Lewis Martin

Whereas many researchers and mine engineers have conducted tests using different types of grout, grout ratios, and physical modifications of the cable to determine cable bolt load characteristics, few studies have been conducted on cables fitted with internal instruments. Those studies that have been done have concentrated on cable behavior averaged over significant cable lengths. Researchers at the Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and Health in Spokane, WA, are investigating the physical properties of cable bolts by replacing the conventional king wire with a modified king wire on which strain gauges have been installed . This paper documents test results on these modified cable bolts. Three tests were conducted at SRL on 1.83-m-long cables grouted into two 0.91-m-long pull-tube assemblies. Load along the cable was monitored with 20 strain gauges installed along the length of the cable. The instrumented cable bolt provided reproducible point measurements of cable load as opposed to load measurements averaged over significant cable lengths. Such point measurements can assist in interpreting the influence of cable confinement, grout quality, rock mass stiffness, and other factors. The instrumented cable bolt is a practical field and research tool because it can predict point loading along the cable and thereby allow interpolation of maximum possible loads on a cable.

May 1, 2002

By C. Pattenden

The viability, self-reliance and resilience of small communities are perennial challenges in regional Australia. Recent developments in Australian mining regions seek to govern the minerals industry in a more holistic way that contributes to sustainable futures for affected communities in different contexts. In some areas of the State of Queensland land use conflicts and the cumulative impacts of multiple projects and activities across time and space have come to the fore. In more isolated regions of Western Australia the dominant issues relate to overstretching people, infrastructure and services in predominantly mining towns. In both cases, there is an ambition for regional towns with a strong extractive industry presence to transition into desirable, liveable and affordable cities with a diversified economy. The paper analyses two strategies - the Pilbara Plan in Western Australia, and the Sustainable Resource Communities Policy in Queensland - to identify how these governance instruments are contributing to sustainable development.

Jan 1, 2011