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By Edward Saibel

THE object of this study is to investigate the effect of prior tensile strain on the fracture stress of a metal. This is done in a theoretical manner starting from the point of view developed by the author in his thermodynamic theory of the fracture of metals. The results are compared with experimental findings and a rational interpretation is given to work that shows the variation of fracture stress with prior tensile strain. THEORY OF FRACTURE In the thermodynamic theory of the fracture of metals developed earlier,1 it was shown that a critical strain energy per unit volume exists. This is characteristic of the material and may be calculated from basic thermodynamic data. When the area under the flow curve reaches this characteristic value, fracture occurs. The general criterion for fracture is expressed in the form u ± uo = JLm?AV/V [1] where Lm, is the latent heat of melting of the unit volume, ?V/V is the ratio of the change in volume of the unit volume to the original unit volume on passing from the solid to the liquid state, [uo] is an initial energy density, and J is a conversion factor, which changes energy from heat to mechanical units. As a first approximation, it will be assumed that the stress-strain curve is the straight line that extends from the point of maximum load onward, extrapolated back to the axis of zero strain, for example, line AC of Fig. 1. If the point of intersection of the straight line with the axis of zero strain is represented by so, and the slope of the straight line is p, the analytic form of the flow curve is [s = s + pd [2]] and the strain energy per unit volume evaluated from [JvdS] becomes (vsod + pd2/ 2). When this latter term reaches the critical value JLm?V/V (designated hereafter by M), it is assumed that fracture occurs. This leads to the following expression for the fracture stress: [s1 = \/C r.2 + 2Mp [31] The strain at fracture may be calculated from Eqs 2 and 3. It is assumed in this paper that the initial energy density is either zero or that it may be neglected. Furthermore, the complicated states of stress and of strain existing in the necked region of the tensile specimen after "necking" has occurred will also be neglected for the present, so that average conditions will be assumed to prevail. FLOW AND FRACTURE CURVES Ludwig2 attributed to materials two fundamental properties: (I) a resistance to flow and (2) a resistance to fracture. He reasoned that at each instant the

Jan 1, 1947

By R J. Thompson

In truck-based hauling systems, the mine haul road network is a critical and vital component of the production process. As such, underperformance of a haul road will impact immediately on mine productivity and costs. Operations safety, productivity and equipment longevity are all dependent on well-designed, constructed and maintained haul roads. With the advent of autonomous haul trucks, the haul road itself becomes all the more critical to the success of these type of operations; not only in relation to mine operators requirements for safer and more efficient and predictable haulage systems, but also in response to autonomous truck manufacturers’ requirements for a more predictable and controlled operating environment. This paper presents a brief summary of the state-of-the-art in surface mine road design and then proceeds to examine the design and technological challenges associated providing a safe, predictable and affordable road for autonomous mine haul trucks. The paper serves as a basis for evaluating the contributions that enhancements in road design and management can deliver to autonomous mining operations, an initiative that also has scope for adoption within the operating life of many mines, haul roads and haul trucks.

Nov 22, 2011

By J. D. Jones

The geographic occurrence of economic mineral deposits presents a variety of problems in modern tailings disposal operations. This paper presents case histories in several sectors of the mineral industry as well as the several stages of operations planning required for new designs, system expansion, reactivation of abandoned systems and upgrading to present environmental standards.

Jan 1, 1978

By Demaerel. J. P.

Arsenic plays a major role during electroreflning of copper. Both the arsenic content in the anode and the arsenic concentration of the electrolyte have, in conjunction with other impurities such as lead, antimony, bismuth and oxygen, a direct influence on the quality of the cathode. The mechanisms are currently slime. inclusion and precipitation of insoluble compounds in the bulk of the electrolyte. Arsenic has also been reported to have a depassivating effect on the anode. An influence on the anode slime adhesion has also been found. A literature survey is given and these data are compared with and completed by our own results based on lab and pilot scale experiments as well as on Olen tank.house practice.

Jan 1, 1987

By Hugh R. Rhys

The question of the desirability of recovering cullet from MSW in order to recycle it into the manufacturing of glass containers remains a controversial one. The main factors appear to be: 1. The position of the Glass Container Manufacturers Institute (GCMI), as the trade association for most container manufacturers, is that post-consumer cullet is a vital source of raw material. Present requirements are for: a) Flint cullet b) Non-flint cullet of known mix proportions c) Mixed unsorted cullet of known mix propertions c) Mixed or non-flint cullet of unknown mix proportions. A market balance for these products exists, and this might somewhat limit the outlets for (b), (c) and (d), or severely limit the outlet for (d) alone. 2. The color specifications are rather strict. With cullet admixtures of 20% of the melt or more, and the use of decolorisers in a flint furnace discouraged because their action is reducing in a process which requires an oxidising environment, color contamination in a flint furnace is serious.. For amber and green furnaces (reducing) it is less serious, but in order that the quantity of decolorisers may be controlled, the color balance (as a measure of the Fe and Cr content) of the admixtured cullet should be known. 3. Why not simply color analyze, either by a continuous on-stream or off-stream: photo-electronic analysis, or by systematic batch sampling (with some kind off electronic surveillance of the mainstream) and just send mixed, color measured cullet to only amber and green furnaces? The flint would-be simply included in the mix. This is probably technically feasible, but is subject to the market limitations noted in point1.

Jan 1, 1975

By Mihaita Matei

An adaptive approach to control the deformation in tube hydroforming process is presented. This requires: the use of an existing non-linear FE software (ABAQUS) that incorporates a user material model (VUMAT), the development and implementation of an adaptive control strategy to coordinate the internal pressure and the axial load so as to prevent fracture and wrinkling failures (knowledge-base controller) and the application of the developed adaptive simulation approach for finding the optimal loading path required to hydroform a defect-free part with as uniform thickness distribution as possible (user's load subroutine (VDLOAD). In order to validate the approach, the case of conical hydroforming and the case of bending followed by hydroforming component is discussed.

Jan 1, 2011

By Ish Grewal

"Batch centrifugal gravity concentrators, which produce very high ratios of concentration, have become common place for recovering free gold within milling circuits. Their effectiveness has proven to be especially useful in recovering finer gold particles. The knowledge related to testing, modeling and scale-up of these systems has been well established over the recent decade mostly due to the efforts of the late Dr. Andre Laplante.Gravity separation technologies such as jigs, spirals and shaking tables can provide the increased mass yields required for minerals that occur at higher concentrations than gold, however their effectiveness tends to diminish at finer particle sizes. The development of high mass yield centrifugal concentrators has provided the opportunity to be able to recover a wide range of minerals at finer particle size classes when compared to the more traditional gravity concentration devices. These concentrators also provide additional benefits such as smaller unit footprint and automated operation.This paper discusses the background, current practices and future applications for high mass yield centrifugal concentrators in base metals, sulfides and industrial minerals. Bench scale, pilot scale and plant practice examples are also presented.INTRODUCTIONGravity concentration, one of the oldest mineral beneficiation processes, has evolved over the decades and continues to play an important role in modern mineral processing operations. The development and growth of froth flotation in the early part of the twentieth century led to a decline in the importance of gravity concentration. However, gravity concentration continued to be used for ores that are difficult to beneficiate using froth flotation; such as tin, tungsten, niobium/tantalum, iron, industrial minerals and oxidized coal. In recent decades, many operations have begun to employ a combination of both gravity concentration and froth flotation Since flotation relies on surface chemistry and gravity concentration relies on specific gravity differences, putting these techniques in series provides today’s metallurgist with unprecedented opportunities to maximize grade and recovery of many of these minerals."

Jan 1, 2009

By F. W. Lee

The paramount importance of water to life of all forms on the earth is too well known to require elaboration in this brief paper. It has repeatedly been termed the most valuable of all our mineral resources. Its importance is justifiably recognized in the extensive areas covering the earth which receive sufficient rainfall to sustain a relatively luxuriant vegetation; but in those areas where rainfall is insufficient to support anything but a relatively meager plant growth, the location of a water supply and its development become of even more vital interest to those attempting to obtain a living from the soil. Geological investigations concerning the water supply of the United States have been most extensive, important work having been accomplished by Federal, State, and local governments and by private enterprise. A casual examination of the titles of the 739 Water-Supply Papers published by the United States Geological Survey3/ alone testifies 'to the vital nature of our water resources and the extensive work that has been done on them.

Jan 1, 1936

By Marlies Grimmer, Frank Amo Boateng

One of the challenges of mining is the concentration of heavy metals it releases into the environment through a phenomenon called Acid Mine Drainage. Freiberg is no exception due to its long mining activities. The European Union proposes that all rivers and streams must be in a good ecological status by the year 2027 but this would be difficult for large water sources as it would be economically unviable. Consequently, the approach of treating these waters at point sources would be of immense help and hence this column experiment on mine water treatment with carbon sorbents to remove zinc form the Rothschönberger Stolln. For this experiment three resins namely, APTsorb, activated coke, charred fermentation residues (which was produced by the Freiberg University of Mining and Technology) were analyzed through a simple column experiment to determine their sorption capacities. Through their sorption capacity as this experiment seeks to ascertain: we are able to make suggestions scientifically on the best material among the three for the future design of a treatment plant for the RSS. After the experiment whereby a 10 ml peri glass column was used, material A: APTsorb showed the least adsorption capacity (0.01 meq/g) and this could be attributed to the fact that the resin works well under pre-determined parameters such as pH and surface area. Material B: Activated coke showed a better sorption capacity (0.53 meq/g) in comparison to the basis value used for this experiment. Material C: charred fermentation residue which was produced by the University showed the most efficient capacity of (1.69 meq/g). This in comparison with the value used as the basis for this experiment showed that material C (charred fermentation residue) is very efficient for zinc sorption. pH values measured at the effluent of all the experiment were slightly higher than the pH measured in the initiating water.

Feb 1, 2024

By Kathryn C. Sole

A novel solvent-extraction process for the refining of gold was recently commercialised, with the commissioning in May 1997 of a 24 t a-' refinery at Harmony Gold Mine in Virginia, South Africa. The MinataurTM Process (Mintek Alternative Technology for Au Refining) uses solvent-extraction technology to produce gold of 99.99% purity from the cathode sludge arising from a conventional carbon-in-pulp / electrowinning circuit. Implementation of this process introduces significant cost benefits compared with the conventional dore smelting / toll-refining route previously followed. This paper outlines the process, presents selected operating results obtained during the first few months of operation, and provides some details of the associated techno-economic advantages.

Jan 1, 1998

By M. Cross

INTRODUCTION The results of the Japanese dissective investigations have [l-4] transformed our understanding of how the blast furnace operates. These studies revealed an internal structure of the furnace burden with five main zones, as illustrated in Figure 1. In the granular zone the charged material retains its structure whereas in the cohesive zone the iron ore particles are at advanced stages of reduction and form a semi-molten mass with a relatively high flow resistance. In the active coke zone molten iron and slag flow through a matrix of loosely packed coke. The raceway is a relatively small void space generated by displacement of coke due to the hot blast momentum, whilst the hearth is packed with coke, slag and molten iron. [ ] It is now well appreciated that furnace control is largely achieved and maintained by using the burden charge distribution to determine the gas glow distribution within the furnace and, hence, the shape and extent of the cohesive zone. In fact, Wakayama et a1 [5] of Nippon Steel Corporation state that optimum furnace operation is synonomous with the formation of a desirable cohesive zone shape, which in turn is almost solely determined by the burden charge distribution and its mechanical properties [6]. Much of the development work on operating furnaces since the dissective investigations has been oriented towards the identification of external furnace measures which reliably predict the shape of the cohesive zone. Currently the most popular measures are top gas temperature, velocity and CO/CO, ratio profiles [5]. More recently pressure distributions as evaluated from a series of wall measurements down the height of the furnace are also being utilised [7] to identify the position and shape of the cohesive zone. A great deal of emphasis has been placed upon achieving a consistent quality in the burden charge materials, establishing a suitable set of operating conditions and only making changes when forced to, ie., the operation for some reason moves outside a desired operating range or the production requirements change. Operational control schemes based upon this philosophy (eg., Kawasaki's GO-STOP system [8]) have been remarkably successful at achieving both high production rates and relatively low fuel costs. Mathematical models have long been used as tools to assist in the analysis of the blast furnace process. Although, the models have been useful in post-operative analysis and for identifying trends, etc., they have not proved reliable for detailed design criteria or as the basis for effective control schemes. Such mathematical models have moved from simple statistical correlation, through overall and stagewise heat-and-mass balance calcu-

Jan 1, 1984

By QinGuo, Shenghui Guo, Jinhui Peng, Linqing Dai, Libo Zhang

This paper adopts a simple and novel preparation. Taking cellulose as a template, a tubular morphology structure of micro/nano ZnO crystals was obtained by microwave roasting at high temperature. The higher the microwave roasting temperature, the larger the degree of crystallization. The experiments indicate that the best photo catalytic effect can be obtained at 850 : At this temperature, the oxidation of cellulose is complete. Large quantities of hexagonal shaped ZnO crystal can be observed, specifically the (0001) crystal face. Under ultraviolet-visible irradiation, taking long arc mercury lamp as light source, the material had good photocatalytic activity. The decomposing efficiency of methylene blue reaches 97% in 60min, which is superior to that of preparations without templates at the same temperature.

Jan 1, 2016

By M. Ramprecht, M. Wu, A. Kharicha, A. Ludwig, H. Holzgruber

"The influence of the frequency of AC power supply on the magneto-hydrodynamic during the electroslag remelting process is studied. The focus is on the electrodynamic field and its resulting mechanical effects on the flow and liquid interfaces. The possible influence of the electrochemistry on the droplet formation is qualitatively discussed.IntroductionThe electroslag remelting (ESR) process is a secondary melting technique which can be used for a variety of metals and alloys, provided appropriate fluxes (slags) and melting parameters are employed. The ESR process is presently operating mostly with AC current of about 50 Hz. However for reasons primarily of inductive losses in the electric circuit, furnaces for ingots larger than 1 m, use or are projected to use current of very low frequency (< 5 Hz). Effects of lower frequencies (2.5-5Hz) on macrostructure and non-metallic inclusions were recently studied by Chang [1]. Most of investigations were performed either with DC power or with AC of 50-60 Hz [2-4]."

Jan 1, 2012

By Jr. Schnakenberg

In 1986 the U. S. Bureau of Mines (USBM) embarked on a major research effort to develop technology that can substantially reduce worker exposure to face hazards simply by relocating the equipment operators to an area of relative safety. This reduced exposure mining system (REMS) research effort enhances the USBM ongoing health and safety research efforts to reduce and control dust and noise and to reduce accidents through training and better mining practices. This paper reports progress of the research that is developing and will demonstrate the technologies required for the computer-assisted tele-remote operation of continuous mining machines, haulage systems, and roof bolting machines.

Jan 1, 1996

By M. E. Lombardi

IN comparison with the mining industry the petroleum industry is new and inexperienced, and until now it might have been called the fortunate industry. Its great good fortune consisted in two things; a bountiful supply hidden by nature in the rocks of the earth, and a steady and large increase, during the past twenty-five years, in the demand for petroleum products. It is a remarkable fact that consumption of gasoline in the United States has shown an increase every year since automobiles first became important, and even in 1930 there was a four per cent increase, in spite of the universal depression; the estimated increase if the times had been normal, was ten per cent. This industry has, therefore, not passed

Jan 1, 1931

"The Dumont deposit is a large (1066 Mt probable reserve) low grade (0.27% nickel), nickel sulphide project located in the Abitibi region 25km west of Amos, Quebec. Royal Nickel Corporation acquired the project in 2007 and has since taken the deposit through pre-feasibility. And updated, revised pre-feasibility was released in July 2012.The disseminated nickel sulphide and alloy mineralization is hosted within the serpentinized dunite subzone of the Dumont Sill; a differentiated, pervasively serpentinized, ultramafic sill of komatitic affinity. Pentlandite, heazlewoodite and awaruite are the dominant nickel-bearing, metallic phases and can be recovered by conventional methods (flotation, mag separation). Non-recoverable nickel is also present within the silicate matrix of the serpentinized dunite and is locked in serpentine (Fe and Mg-rich variants) and minor olivine.A detailed mineralogical program including 1097 QEMSCAN® samples and 4300 electron microprobe points were undertaken to increase the understanding of the nickel deportment in the various recoverable and non-recoverable phases in a spatial context across the deposit. Eighty-three (83) metallurgical tests performed under a standard procedure have linked the mineralogy to metallurgical performance. This has allowed the creation and modelling of geometallurgical domains on a block by block basis to understand the recovery variation and metallurgical performance throughout the deposit. Understanding the spatial variability of Ni deportment in recoverable and non-recoverable phases through mineralogy is the key to understanding metallurgical performance thus, unlocking the value of the Dumont deposit and other large tonnage low grade ultramafic nickel deposits."

Jan 1, 2013

By Osamu Iida

Since &apos;start-up of the larger Mitsubishi Continuous Copper Smelting Process in 1991, furnace relining campaign was gradually prolonged to once every 2 years according to deregulation of governmental boiler inspection. On the other hand, in 1998 Naoshima smelter embarked on an intermediate strategic expansion plan to strengthell its international competitiveness. As part of this plan, modifications were implemented in the copper smelter designed to increase output of anodes from new charge source to 270,000 tpa. In May 1998, treatment of dried neutralized residue was started in C furnace, and during the shutdown for brick relining in April 1999, intensive modifications to the boilers as well as the installation of new spray coolers for furnace off gas treatment were implemented. Finally, the new larger oxygen plant was commenced its operation in May 2000 and the expansion was achieved around 30% increase of anode production from original design.

Jan 1, 2001

By Vinay Kumar

The disposal of large quantities of electronic scraps generated world wide is causing not only environmental problem but also loss of resources. Therefore, R & D efforts have been made to develop a suitable process for extraction and separation of metals viz. copper, zinc, cadmium and nickel expected from the leaching of e-scraps using solvent extraction process. Different process parameters viz. pH, aqueous to organic ratio, kinetics of extraction, extraction isotherm to establish stage requirement for extraction in continuous mode etc have been studied to optimise the condition for the separation of metals. The studies showed the selective extraction of copper after iron precipitation from the sulfuric acid leach solution of e- wastes containing ~1.0 g/L Cu and minor impurities with 2-hydroxy-5- nonylacetophenoneoxime (LIX 84) above pH 2.0 in single stage. A scheme for separation of cadmium, zinc and nickel has been proposed using di(2-ethylhexyl) phosphoric acid (D2EHPA) under controlled pH of the aqueous solution. The order of extraction was found to be Zn> Cd> Ni.

Jan 1, 2009

By Bowler Jonathan, Lorraine Kent, Tereza Crisu, Stuart Walker, Nicholas Lightfoot

"It has been the practice in Europe to extract the most economic seams first: taking the seams sequentially, top down, to avoid operating within the fractured strata formed by the subsidence trough above previously mined coal seams. In the 1990s, the UK coal industry found itself at a number of sites having to operate over one or more previously mined seams. This led to specific geotechnical challenges with respect to maintaining economic, safe and stable rectangular roadways with rock-bolted support.Within this paper, the current challenges and mitigation strategies of overmining in the UK are described following the completion of a -three-year European Commission-funded project in 2015. The challenges and mitigation strategies are related to:• A case study with overmining of older workings of variable geometry;• Numerical modeling for overmining layout and support design; and• A case study site planning mine layout when considering future overmining.INTRODUCTIONAt the first case study site, case histories were examined for a mine operating at a depth of approximately 700 meters where five longwall panels were extracted above workings 35-40 m below. The overmining of various extraction geometries below led to challenging conditions in areas of high vertical stress concentration. It was found that results from one longwall panel could be suitably used to predict behaviour in a subsequent panel. The experience was used to update previously existing guidelines on the positioning of roadways in relation to subsidence troughs. Existing guidelines recommended that only as a last resort should longwalls be planned to retreat over narrow pillars, or from solid ground into a subsidence trough. Existing guidelines regarding the layout of overmining panels are conservative, and new work indicates that such multi-seam geometries are possible with appropriate support management strategies."

Jan 1, 2016

By Anthony R. Przybylek, John M. Visnesky

INTRODUCTION Thermal dryers have been utilized for reducing moisture of bituminous coal since the late 1930&apos;s. Since that time, numerous changes in the coal industry have motivated advances in thermal drying technology. The purpose of this paper is to discuss the changes that occurred to dryer design and focus on current practices of fine coal drying. The major topics discussed in this paper are: - Early Thermal Dryer Design and Evolution - Current Drying System Design and Associated Components - Current Economics of Fine Coal Thermal Drying - Future Markets and Design Considerations EARLY THERMAL DRYER DESIGN AND EVOLUTION Background The practice of drying fine coal with heated air has been performed for more than one half century. Throughout that period, both Metallurgical and Steam coal producers have used this method for reducing the surf ace moisture content of their fine plant products. During the late 1930&apos;s and early 19401s, vibrating bed and flash dryers were used to per- form the drying duties. Closed water circuits and vacuum filtration had not yet been integrated into process circuitry and centrifugal dryers were in their early stages of development. During that same period, changes in mining practices were reshaping the distribution of coal to our processing facilities. Plants originally designed for the purpose of processing coarser fractions of coal were being burdened with additional quantities of fine coal. Those plants, unable to recover fine coal, would reject these solids to plant bleed. The higher incidences of stream pollution that resulted from these events prompted clean stream legislation and the need for new, more efficient fine coal recovery circuits. The coal processing industry responded to these needs by integrating closed water circuits and filtration into circuits. The fine coal filter cakes recovered exhibited poor handling characteristics by themselves and often required further dewatering to improve their characteristics. Flash dryers at that time were being used to dry the coarser products. For those facilities operating flash dryers, the solution to this new problem appeared to be simple. The filter cake was combined with the coarser (-1/4") coal and then introduced to the flash drying column for drying. The filter cakes, however, presented significant problems for the flash drying systems. Heavy lumps of filter cake could not be dispersed and conveyed by the rising hot air and as a result would settle out in the bottom of the column. This material, known as "drop-out", would then accumulate and require further handling. The solution to this problem was not an easy one. Sophisticated mixing equipment was employed to condition the feed to the dryers. As attempts to minimize drop-out with this approach failed, the only recourse was to collect the material with conveying systems and recycle it back to the plant or dispose of it. The additional costs of handling this material reduced the attractiveness of the flash systems and opened the door for the development of a new, more cost effective coal drying system. Due to the nature of the problems experienced by the flash systems, fluid bed systems were considered. Fluid bed dryers were being used in other industries at that time but had no operating history in the coal industry. Dorr-Oliver transferred technology from other industries and built the first fluid bed drying system for fine coal.

Jan 1, 1988