Search Documents

By Fábio de Oliveira Braga

Um sistema de blindagem multicamada consiste de uma camada frontal de cerâmica, uma camada intermediária de fibras sintéticas ou de material compósito, e uma camada posterior de um metal dúctil. Recentemente, há o interesse em substituir as fibras sintéticas por fibras naturais, por suas propriedades adequadas, menor custo e peso. O objetivo deste trabalho é avaliar o desempenho de compósitos de matriz poliéster reforçados por fibras naturais de Curauá em blindagens multicamada. Placas com 0, 10, 20 e 30% vol. de fibras integraram a blindagem que sofreu impacto balístico com munição 7.62 mm, e o dano foi avaliado pela indentação característica em plastilina e por uma análise microscópica das superfícies de fratura. Foi mostrado que a blindagem resiste ao impacto balístico, atendendo à norma NIJ-0101.04 para o nível de proteção III. Além disso, as fibras de Curauá são responsáveis por manter a coesão do compósito após o impacto balístico, e o compósito por dissipar parte da energia do projétil por mecanismos como delaminação, trincamento da matriz, fratura e descolamento das fibras.

Aug 16, 2017

By Alfred Bellows

The objective of this contract is to design, build and demonstrate a support system to improve roof control in the entries of longwall mines. The objective of this phase has been the detailed design of such a system and the selection of a test site in which to perform the pilot demonstration. The result is a complete set of detail drawings or specifications which define the three major components of the system. The Gate Support is a variation of a face chock which has an extended canopy and additional hydraulic legs to protect the region of the face-entry intersection. The Entry Support is a steel beam and hydraulic prop set which is reusable and serves to support the first 100 or more feet of entry inby the longwall face. The Transporter is a bolter-like vehicle with a crane used for installing and retreating the beam sets. The test site selected is CF&I's Allen Mine in Colorado. They presently use simi¬lar steel beams and expect the FMA support system to be more effective as well as recoverable. It is recommended that the completed drawings be used to build a prototype system and test it first in a remote section of the mine and then in the active longwall tail entry.

Jan 1, 1978

By M. C. Azar, W. B. Mason, G. L. Anderson

Eminent domain overview Eminent domain is the power of the Government or a municipality to take property for public use without the consent or acceptance of the owner. Typically, the agency taking the prop¬erty will make an offer, hoping the owner will immediately accept and allow work to begin. If a mutual resolution regard¬ing its value cannot be reached, how¬ever, the municipality will institute a condemnation action in court seeking possion of the property. This is when the problems begin. The power of the Government to take the subject property is limited by Federal and state constitu¬tional requirements to pay "just com¬pensation" for the property. The exact nature of an owner's prop¬erty has been the subject of much debate and discussion. It is generally under¬stood, though, that property is consid¬ered to be "every kind of right or inter¬est, capable of being enjoyed and recog¬nized as such, upon which it is practi¬cable to place a money value" (US vs. 53 114 Acres of Land). A taking, for condemnation purposes, is considered to occur whenever there is a substantial interference with the free use and enjoyment of the property. Rarely is the necessity for the taking ever challenged and more rarely is the taking ever successfully challenged. When a taking occurs, it is not only the fee owner who is entitled to compen¬sation. Every person holding an interest in the subject property will be recog¬nized. Thus, all persons who at the time of taking have a compensable interest in the property will be made parties to the case (Swanson vs. US). Minerals, like all other interests in land, are recognized as property rights, giving the owner the power to dispose of them as he or she sees fit. Thus, the only remaining considera¬tion is only "just compensation." Ex¬actly what "just compensation" is has been difficult to define. Generally, it is that amount of money that will "put the person in as good a position as the per¬son would have been in had the taking not occurred." The owner must not be forced to sacrifice or suffer by receiving less than full and fair value for the prop¬erty. Every element that effects the value of the land and that would influence a purchaser must be evaluated. Courts have employed a variety of techniques to determine just compensa¬tion but have generally relied on market value as the standard for measuring compensation to the owner. The deter¬mination of market value is based on sales, income, costs, and use. These factors have been employed in various ways but can be summed up as: -The highest estimated monetary price the property will bring if exposed for sale in the open market with a reason¬able amount of time allowed to find a purchaser who is buying with knowl¬edge of all the uses and purposes to which it is adapted and for which it is capable of being used. • The amount the property would bring if it were offered for sale by one who desired, but was not obliged, to sell, and was bought by one who was willing, but not obliged to buy. • What the property would bring in the hands of a prudent seller, at liberty to fix the time and conditions of sale. • What the property would sell for in negotiations resulting in sale between an owner willing, but not obliged to sell, and a buyer willing, but not obliged to buy. • What the property would be rea¬sonably worth on the market for a cash price, allowing a reasonable time to affect a sale. (Michigan Standard Jury Instructions). Special consideration regarding mar¬ket value is given when the taking is only partial, rather than complete. An example of this partial taking is when a state highway cuts across the northern half of a parcel of property, leaving the rest behind for the owner. A variety of problems can be immediately seen. In a partial taking, the owner is permitted to recover not only for the property taken, but also for any loss in the value of the remaining property. The measure of compensation for partial taking purposes is generally the difference between the market value of the entire parcel before the taking, and the market value of what is left of the parcel after the taking (Michigan Stan¬dard Jury Instructions). Determining the partial taking value for mineral bear¬ing lands is the difficult issue.

Jan 1, 1989

By William F. Hahn

This project focused effort on three separate areas: demonstration of a low seam longwall illumination system, design of illumination systems for low coal auger miners, and an assessment of machine lighting systems for machinery used to mine low seam coal. Results indicated illumination systems can be purchased by the mine operators of low coal seams. These systems can be supplied with the equipment as a factory integrated system or can be retrofitted to the machine or longwall equipment.

Jan 1, 1982

By Marcelo de Oliveira Lima

O cenário energético brasileiro nas últimas décadas apresenta períodos de escassez na oferta de energia elétrica. Essa realidade impacta o setor industrial por representar um risco operacional e fortalece a necessidade de aumentar a eficiência energética dos processos. Adicionalmente, a eficiência contribui para a melhoria nos resultados financeiros e minimiza impactos ambientais. Nesse contexto, o uso de iluminação LED se destacou nos últimos anos como alternativa às tecnologias tradicionais. No entanto, inicialmente os preços das lâmpadas e luminárias LED eram proibitivos. Esse trabalho apresenta um histórico do custo dessas lâmpadas em diferentes aplicações típicas à uma empresa siderúrgica e demonstra que atualmente o LED pode ser considerado atrativo em algumas delas. São apresentados também casos de sucesso implantados na AcelorMittal Tubarão, garantindo inclusive melhoria nos índices de iluminamento. Por fim, é apresentado de forma sintetizada o Programa de Eficiência Energética da ANELL que disponibiliza recursos das concessionárias de energia para implantação de projetos, sendo ilustrados exemplos de projetos reais e suas economias de energia utilizando iluminação à LED.

Oct 30, 2017

By Kíssia Carolina Bertoluci Cardoso

Para a fabricação de peças de grande porte, o forjamento em matriz aberta é o processo mais utilizado. Porém, se seus parâmetros não forem bem estabelecidos, defeitos metalúrgicos poderão surgir; esses, em sua maioria, provindos do material bruto de fusão, como rechupes e vazios. Para sanar tais defeitos, a deformação imposta na peça deve ser a mais homogênea possível. Neste estudo, a simulação numérica foi utilizada para verificar a relação entre a largura de contato matriz-peça e a espessura da parede de peças vazadas, com o objetivo de analisar o conceito de razão de mordida para esse tipo de geometria. Utiliza-se um billet cilíndrico inicial de 450 mm de comprimento, 360 mm de diâmetro externo e 120 mm de diâmetro interno, de material AISI 4140. As razões de mordida estudadas variam entre 0,2 e 1,4, sendo impostas variações de tempo em cada processo. Após análise, pôde-se verificar que as geometrias que apresentam distribuições mais homogêneas de deformação utilizaram razão de mordida de 0,4.

Aug 16, 2017

By Joaquim Luiz Monteiro Barros

O atendimento as normas ambientais vigentes nos diversos processos das siderúrgicas no Brasil, mais do que uma exigência legal, deve ser um compromisso da empresa com os funcionários, clientes e com a sociedade como um todo. O perfeito dimensionamento do sistema de limpeza de gases e a aplicação de filtros de mangas horizontais é, com certeza, uma alternativa eficiente para solucionar de forma adequada as particularidades e necessidades dos diversos processos siderúrgicos.

Aug 17, 2017

By Rosa Maria Sales da Silveira

O objetivo do presente trabalho foi caracterizar a camada de óxido formada na superfície externa de tubos de reforma retirados de serviço após diferentes tempos de operação, em função da temperatura em que os mesmos estão expostos que varia com altura dos tubos. A caracterização consistiu da análise morfológica da camada de óxido utilizando um microscópio eletrônico de varredura de alta resolução e mapeamentos de composição química por EDS para verificar a distribuição dos óxidos presentes na mesma. Observou-se que a distribuição dos diferentes óxidos apresentou uma sequência padrão e que a camada de óxido aumenta com a temperatura e tempo de operação, bem como a camada subsuperficial empobrecida de carbetos de cromo.

Oct 30, 2017

By Isabel Ferreira de Barros

O objetivo deste trabalho é avaliar o efeito da frequência de pulsação da corrente de soldagem sobre a microestrutura e propriedades resultantes de solda de chapas finas do aço inoxidável austenítico AISI 316L. Chapas do aço inoxidável AISI 316L foram submetidas à soldagem variando a frequência de pulsação de 2 a 8 Hz, mantendo-se constante a energia de soldagem. Os parâmetros de soldagem foram selecionados de forma a se obter penetração total. Foram realizadas análises das características superficiais. A microestrutura da seção transversal foi avaliada por microscopia óptica e microscopia eletrônica de varredura. A avaliação da resistência mecânica foi realizada por meio de ensaios de tração uniaxial, dureza e dobramento. Os resultados têm mostrado que variações na frequência de pulsação não atuaram de forma a conferir melhores propriedades mecânicas à junta soldada.

Aug 7, 2018

By R. L. Grayson

For the years 1990 and 1991, West Virginia's underground coal small-mine fatality rate « 20 employees) was approximately ten times higher than the national coal industry rate. Although the total number of fatalities decreased to 17 in 1992 (from 22 in 1991), West Virginia still led ,the nation in coal mining fatals. A team of mining and safety professionals from West Virginia University studied the problem over the past year, interfacing with the Mine Safety and Health Administration and the West Virginia Office of Miners' Health, Safety and Training. A clear path for 'formal intervention was determined and is presented here.

Jan 1, 1994

By Alexandre Gonçalves Andrade, Crisley Dellaqua Pacheco, Gabriel Miranda Teixeira, Aline Maria Santoro Nasaré, Tatiane Ferreira Alvarenga

Diffuse emissions are that directly related to particulate matter suspended from civil structures, materials disposed in conveyor belts carried out by wind, stack e reclaimers operations and that one where dust collectors are not able to act correctly. Vale implemented in the last years a unique system capable to measure this kind of dust, called RAMPs (Dust Monitoring Automatic Network), which creates an analytical net in Tubarao industrial site, located in Vitória, ES. In order to prevent diffuse emissions in Tubarao’s pellets stockyard, it was proposed and developed a predictive model based on operational and climate variables available on the site, using big data and advanced analytics tools. The models developed shows to be adherent to the real emissions rates measured by the RAMPs and proved to be an efficient tool to predict emissions over the internal target with 4 hours of precedence.

Oct 1, 2019

By Boo Hyun Nam, Berk Turkel, Luis G. Arboleda-Monsalve, Jorge E. Orozco-Herrera

Construction of buildings, roads, and traffic activities generate vibrations to urban infrastructure. The vibrations produced by construction activities have an impact on the soil through which they are transmitted. These effects become much more significant in granular soils. The soil conditions in Florida consist mainly of sandy soil deposits and this makes driven piles a commonly used method. In the design of deep foundation installations, it is significant to consider the potential construction issues related to the driving process. This process generates vibrations in the surrounding soils and thus, its effects on nearby soils and structures must be considered. This paper presents a web-based survey conducted among geotechnical engineers in Florida to better understand the common practice and experience regarding the effects of pile driving on surrounding soils and structures. The perception of different practitioners in the state of Florida on ground deformations and damages to adjacent structures induced by deep foundation installations are investigated. The engineers who have experienced ground vibrations and deformations were asked to define the susceptible soil conditions and main triggering factors of large ground deformations induced by pile driving. Sandy soils with loose to medium relative densities were found to be the most susceptible soil condition to generate ground deformations. Conclusions are drawn regarding the importance of considering ground vibration monitoring during the design phase of deep foundations.

Oct 1, 2022

By Danilo de Castro Denúbila

Neste trabalho, foi avaliada a influência da temperatura de bobinamento após a laminação de tiras a quente em escala industrial na Usiminas, usina de Ipatinga, na microestrutura, na dureza e nas propriedades mecânicas em tração de um aço ARBL da classe de 800 MPa de limite de resistência mínimo. Verificou-se que a microestrutura, a dureza e as propriedades mecânicas em tração (limite de escoamento, de resistência e alongamento) foram pouco afetadas pela variação de temperatura de bobinamento na faixa estudada, entre 470°C e 680°C. Esse resultado está relacionado com o perfil de resfriamento aplicado no processo industrial, que gerou microestruturas formadas predominantemente por uma matriz ferrítica, com pequena quantidade de perlita e bainita. Como a temperatura de início de formação de martensita para o material estudado se encontra abaixo da menor temperatura de bobinamento aplicada, não houve formação significativa dessa fase.

Aug 16, 2017

By João Paulo Ferreira Santos

Neste trabalho, foram obtidas estruturas compósitas constituídas por camadas alternadas de epóxi com mantas de nanofibras de nylon 6. As nanofibras foram produzidas pela técnica de eletrofiação. O comportamento mecânico destas estruturas sob tração e sob impacto pendular IZOD foram estudados. A incorporação das nanofibras na matriz epoxídica permitiu aumentos no módulo de elasticidade (6%), na resistência a tração (7%) e na energia de impacto (2%), ou seja, houveram ganhos de resistência mecânica sem sacrificar a resistência ao impacto, ao contrário do que ocorre na quase totalidade dos micro ou macromateriais modificadores do epóxi.

Aug 8, 2018

By R. V. Ramani

"In Part 1 of this paper, published in the August 1995 issue of Natural Resources Forum, a review of several mining disasters around the world established the complex nature of their causation and their catastrophic effects. The involvement of human beings, either through acts of commission or omission, was highlighted. In Part 2, a discussion of the various approaches to disaster control, mostly as practised in the USA, is presented. A systems approach to disaster prevention incorporating elements of hazard identification, mine design, emergency response and post-emergency audit is presented.In the USA the role of government in the affairs of its citizens is continually growing. This role is intended to ensure an unimpeded pursuit of happiness and prosperity by the population and to curtail actions which are restrictive or harmful to the citizenry. The passage of a legislation is an indication that it has been decided through the established process that the activities covered by the legislation should receive appropriate consideration. The enactment of the Coal Mine Health and Safety Act of 1969 (The 1969 Coal Act), the Mine Safety and Health Amendment Act of 1977 (The 1977 Mine Act) and the Surface Mining Control and Reclamation Act of 1977 (The 1977 Surface Mining Act), was specifically intended to further the role of government in the health, safety and environmental affairs of the mineral industry.Currently, the federal government's responsibilities for mine safety and health are divided among three agencies: the Mine Safety and Health Administration (MSHA) in the US Department of Labor, the Bureau of Mines (USBM) in the US Department of the Interior and the National Institute for Occupational Safety and Health (NIOSH) in the Department of Health and Human Services (National Research Council, 1981). MSHA is responsible for issuing and enforcing mine safety and health regulations, for training miners and for responding to mine emergencies. The Bureau of Mines is responsible for conducting research on mine safety and on the technological means for reducing health and safety hazards in mines. NIOSH conducts research relating to miner health, and together with MSHA, tests and certifies devices used to detect hazardous materials in mines and protective equipment used by miners. NIOSH also plays a public health role in that its activities in mining include health hazard evalua¬tions, general mining surveillance as mandated by law and medical surveillance including coal miner X-ray and autopsy programmes. MSHA shares with the Bureau of Mines the responsibility for integrating R&D results into operational practice. MSHA implements R&D results either by incorporating them into its own operations or by rule making that requires new practices or equipment to be adopted by the mining industry. In many instances, the Bureau's R&D results have been adopted by the mining industry without rule making."

Dec 1, 1996

By Valencia P. Félix

El texto refiere la labor de control de calidad desarrollado en el minado de óxidos y sulfuros del yacimiento minero Cerro Verde. Este procedimiento implica la actualización de los límites mineralizados y leyes, a fin de generar información al Ingeniero de planeamiento y garantizar que el contenido metálico no difiera del contenido en la explotación. Asimismo especifica características de la ganga y elementos accesorios como contenidos de fierro, manganeso y molibdenita durante el proceso de control del mismo.

Oct 14, 1980

By Saulo Brinco Diniz

A textura cristalográfica e a densidade de discordâncias têm um papel importante nas propriedades de vários metais, podendo ser modificada de acordo com os processamentos mecânicos e tratamentos térmicos realizados, além disto, também é influenciada pela estrutura cristalina e energia de falha de empilhamento (EFE). O presente trabalho buscou observar a influência da EFE na textura cristalográfica e na densidade de discordâncias de metais CFC submetidos a laminação a frio. Os materiais usados foram o latão a, cobre e uma liga de alumínio 1050, que possuem baixa, média e alta EFE, respectivamente. Pode-se observar que diferentes níveis de EFE propiciaram, para a mesma redução da espessura após a laminação a frio, distintas texturas nos materiais utilizados e diferentes densidades de discordâncias.

Aug 16, 2017

By André Rosiak

No processo de forjamento a quente, devido aos ciclos térmicos e mecânicos a que o material é submetido, diversos fatores influenciam e ampliam a gama de propriedades mecânicas que podem ser obtidas nas peças metálicas produtos deste processo. A proposta deste artigo é estudar a influência dos fatores tempo de austenitização, temperatura e deformação sobre a variação da dureza do aço ABNT 4140. Para isso, o material foi mantido em diferentes temperaturas, durante diferentes períodos de tempo e, posteriormente, forjado e tratado termicamente em patamares semelhantes aos de recozimento direto e revenimento. Esta pesquisa corresponde a uma das etapas do projeto BRAGECRIM (Iniciativa Brasil-Alemanha para Pesquisa Colaborativa em Tecnologia de Manufatura).

Aug 17, 2017

By C. Gatschlhofer, A. Krammer, H. Raupenstrauch, T. Hochsteiner, A. Holzer, L. Wiszniewski

The rising demand for lithium-ion batteries, coupled with international climate targets, emphasises the need for circular economy and zero-waste recycling approaches. However, so far, no industrial-scaled solutions are available that fulfil global recovery targets. Therefore, a novel pyrometallurgical reactor was developed at the Chair of Thermal Processing Technology at Montanuniversitaet Leoben to avoid lithium slagging and recover volatile elements via the gas phase. Nevertheless, previous results show that several impact factors, including interfering elements or pre-treatment steps, strongly limit the recycling efficiency of black mass. To simulate the black mass and provide feedback on possible influences of pre-treatment steps, cathode material from production with additives of interfering elements was analysed regarding melting behaviour. The results show that formation of a further processable alloy was increased by almost 50% when pretreatment steps were excluded, indicating pre-treatment steps as a major influence to be considered within this specific recycling route.

Jan 1, 2023

By Raymond B. Ladoo

NONMETALLIC minerals (excluding fuels) arid their primary products produced annual in the United States have a value in excess of one billion dollars, or more than that of the metals, yet the lack of expert knowledge of some of the fundamental technical and economic aspects of this most important and complicated business is astonishing. This paper will deal with the economics of this non- metallic mineral field-the business of making money from producing these minerals. The incentive behind all business activity in a capitalistic economy is to make money-to plan so that each dollar invested in property, plant, equipment, services, and so on will return more than a dollar plus simple interest. Of course, business has social, civic, and national duties and responsibilities, but the fulfillment of these is largely dependent upon financial success.

Jan 1, 1939