Search Documents

By I. R. Kramer

Single crystals of aluminum were pulled in tension in a solution of paraffin oil and stearic acid. The critical resolved shear stress did not change with the concentration of the stearic acid solution; however, the extents and slopes of Stages I and II were affected greatly. The observations lend evidence that the weakening effect of surface-active agents is controlled by the rate of desorption of the metal soap formed by the reaction of the surface-active agent and the metal surface. IT has been shown by various investigators1-" that surface-active agents markedly affect the mechanical properties of single crystals. (A surface-active agent, for the purpose of this report, is defined as a long-chain organic molecule which contains one or more polar groups. Usually, however, investigations have considered only molecules having one polar group.) In general, when single crystals are deformed in some solutions containing surface-active agents, the creep rate, Fig. 1, is increased and the yield strength is decreased. The fatigue strength has been reported to be affected also.ll Rehbinder and his asociatesl' explained the "weakening" effect of surface-active agents in terms of physical adsorption. They assumed that a large pressure was created in microcracks which existed on the surface of the crystal." Harper and Cottrell,' from their study of the effects of surface conditions, found that the deformation characteristics of zinc single crystals were not altered by a solution containing a surface-active agent unless the surface of the specimen had an oxidized surface. They concluded that the role of the polar molecule was to remove the strengthening effect of the oxide coating. Later, And-radeetBpresented additional evidence which appeared to agree with this conclusion. In contrast, Klinken-berg et al.7 reported data which confirmed the results of Rehbinder. Using zinc and cadmium crystals which had been cleaned by electrolytic polishing, a large increase in the creep rate was observed when Lle specimens were tested in a 1 pct oleic acid-paraffin oil solution. They also reported that the creep rate

Jan 1, 1962

By Craig H. B. Leitch

"In describing the alteration of porphyry systems, the term ""secondary K-feldspar"" appears to be an oversimplification. A better term would be ""alkali feldspar"" alteration, because in actual fact the replacement feldspars show gradational changes from an albite, which is important in some systems, to an alkali feldspar containing minor orthoclase molecule, to true orthoclase.There are several textural varieties of secondary alkali feldspar present in the porphyry systems studied from British Columbia, Australia and New Zealand. These include, in apparent increasing order of alteration intensity: clear albite (An10); patchwork albite (An5-10); chessboard albite (An0-10); ""irregular albite "" (An0Ab100 to Ab90Or10); untwinned ""anoralbite"" (Ab90Or10 – Ab70Or30); and orthoclase (Ab40Or60 - Or100)·The exploration significance of these varieties of alkali feldspar is that their gradation in composition, from sodic to potassic, may be linked to a corresponding increase in intensity of alteration. Thus, there is a tendency for more sodic alteration feldspars to characterize weak, sub-economic deposits, or the fringe zones of stronger deposits; the more potassic alteration feldspars may provide an exploration vector toward more highly mineralized zones."

Jan 1, 1981

By John J. Jonas, Hong Qin

Cylindrical samples of pure titanium were subjected to uniaxial compression at room temperature, leading to the formation of three generations of twins. Many primary contraction twins were observed as the initial texture was favourable for their formation. Numerous secondary extension twins formed within the primary contraction twins and some tertiary contraction twins within the secondary extension twins. The orientations of these three generations of twins were determined by electron backscatter diffraction techniques and their associated Schmid factors (SFs) were calculated. The formation of the twin variants selected in each generation and the absence of certain potential variants are accounted for by rotating the twinning displacement gradient tensor expressed in the twin system reference frame into the crystallographic reference frame of the relevant neighbouring grain. The presence of the observed primary, secondary and tertiary twins is explained in terms of the ease of imposing the required accommodation strains on the neighbouring grains. By contrast, certain first, second and third generation potential high SF twins were absent because their formation would have required accommodation by the most difficult deformation mode: pyramidal glide.

Jan 1, 2015

By R. R. Oder

Reported are weight, particle size, gross chemistry and magnetism measurements for lithic, mineral and fused soil components separated from five lunar soils using dry, open-gradient, magnetic separation. Pure diamagnetic anorthite, a feedstock for the electrochemical separation of oxygen and metals, has been separated from anorthistic highland soils. In addition, paramagnetic ilmenite has been separated from high-titanium, basaltic mare soils. Ilmenite, a feedstock for oxygen preparation by hydrogen reduction, may also serve as a source of He3 for use in fusion power generation. Agglutinates (vesicular, glassy components containing metallic iron) have been separated from all of the soils. Iron and refractories can be used for space construction. Metallic iron is easily detected in lunar soils by magnetic susceptibility measurements. Based on the exploratory laboratory results, conceptualizations of innovative magnets for processing lunar soils are presented.

Jan 1, 1993

By Richard Schmidt, Lijun Deng, Mohamed Abdelaziz, Weidong Li

Helical piles are widely used as a foundation supporting a variety of different structures. Understanding the axial behaviour of helical piles is required to confirm the engineering design. Helical pile research is often conducted in the field, but this method can be prohibitively expensive in some cases. Geotechnical centrifuge modeling offers an alternative method for the helical pile research and practice. A series of axial load tests of helical piles installed into cohesive soils were conducted on the geotechnical centrifuge at the University of Alberta. The objective was to investigate the effects of inter-helix spacing and soil strength on the axial behaviour of helical piles. Four types of aluminum model helical piles including one single-helix pile and three double-helix piles with various inter-helix spacing ratios were tested. Both compressive and tensile loading tests were conducted. All model piles were instrumented with multiple strain gauge stations. The clay had an undrained shear strength of approximately 50 kPa and 120 kPa. The test results indicate that there is a transitional failure mode between the two widely recognized failure modes, i.e., individual plate bearing and cylindrical shearing. The shaft adhesion was significantly reduced by the helix. Axial capacities were comparable to the field test results.

By M. Menegaki

Restoration of abandoned mine sites is still one of the weak points of mining practice. The latter stands especially for the case of the surface coal and lignite exploitations, where the extended size of the disturbed land and the drastic changes to the geomorphologic features do not facilitate the implementation of a cost effective and environmentally sound reclamation plan. The paper examines the parameters involved towards the legal requirements for the reclamation of the first lignite exploitation in Greece, namely the ?Plakes? mine, located at Euboea, due to the particularities of the site. Then an integrated redesign procedure is presented, aiming at minimizing aesthetic degradation, confronting technical difficulties and preparing the site to accept new uses.

Jan 1, 2005

By Jef M. van der Zel

The idea of veneering rich yellow gold alloys with a low-melting, high expansion porcelain, has been a driving force for metal-ceramic research in dentistry. Since 1990, with the advent of the Carrara System (1), a low firing temperature veneering ceramic allowed the use of gold alloys with a lower content of platinum and palladium than the traditional gold-platinum ceramic alloys and thus a richer yellow color. The earlier high gold-platinum ceramic alloys contained at least 12 percent platinum group metals to allow for dimensional stability when firing the relatively high melting traditional ceramics. This amount of platinum group metals gave the alloys a greyish tinge which made them unattractively steel colored and difficult to present as ?high gold alloys?. In the 90?s the new generation universal low-melting, high expansion gold alloys gained market share at a steady rate, starting in Germany, and have now for a great part replaced the traditional gold-platinum alloys (Fig. 1). The first alloys contained 75 wt-% gold and up to 9 wt-% platinum or palladium. They provided a metal-ceramic system in which a gold alloy having an aesthetic yellow colour is fired on with a dental porcelain tailored thereto. The tailoring is meant in respect of compatible coefficients of thermal expansion, and compatible melting or softening points of metal and porcelain. The major concerns in the beginning were with thermal stability during firing, the thermal expansion coefficient of the alloy against the porcelain (compatibility) and the yellow color. In a later stage, alloys with gold contents in the range of 50-60 wt-% gold were developed in analogy with the pale yellow gold-reduced alloys that were formerly used for crown & bridge work and the white gold-reduced alloys used for metal veneering where gold was substituted in part by palladium.

Oct 1, 2003

By Richard M. Foose

WOULD you like to find a large new ore deposit next year? The answer is as obvious as the question is foolish. But perhaps the question does have some merit if we alter it slightly and ask: What are you doing about finding new ore? This one is more difficult to answer. Possibly you are doing nothing about finding new ore because you have proved reserves for many future years of production. Others may be investing some small percentage of time, effort, and money in mineral exploration, and reserves may be currently adequate, or inadequate, in terms of many future productive years. Still others may be engaged in large-scale mineral exploration programs involving large expenditures of time, personnel effort, and money. In whatever category you may be, a final question might well be asked. Is your current mineral exploration program, or lack of program, consistent with the long-range needs and objectives of your organization and of the mining industry as a whole, and is it designed to stimulate the growth of the industry in future years, or is it only a short-range program in response to some current situation?

Jan 3, 1958

By Plyley WF

Kidston Gold Mine is a 3.5 million tonnes per year operation located 280 kilometres west of Townsville, Queensland. Kidston's ore body consists of 44.3 million tonnes graded at 1.79 grams per tonne gold and 2.22 grams per tonne silver. Full production commenced in March, 1985. During the remainder of 1985, Kidston milled 3.77 million tonnes of ore and produced 213,614 ounces of gold.The ore is comprised of granodiorite, polymictic and volcanic breccias. The degree of oxidation of the rock influences the milling capacity and therefore determines the cut-off grade; ore is categorised as oxide, transition and fresh. The milling rates are 15,400, 12,000 and 9,600 tonnes per day for oxide, transition and fresh ore respectively.The ore is treated in a conventional cyanidation/ carbon-in-pulp plant (CIP). The plant consists of a primary crusher, semi-autogenous grinding (SAG) and ball mills, leach circuit and carbon-in-pulp circuit. Carbon stripping and dore smelting are done on site. The major difference between the Kidston plant and other Australian CIP plants is that a cyclone separation and washing circuit rejects half of the dry tonnage as a sand tail prior to CIP treatment. This difference allows the CIP circuit at Ki.dston to be smaller and makes the CIP less sensitive to the grind circuit product size.

Jan 1, 1986

By W. R. Ingalls

During the last two years, and especially during the last six months, a number of important articles upon the new methods for the desulphurization of galena have been published in the technical periodicals, particularly in the Engineering and Mining Journal and in Metallurgie. I proposed for these methods the type-name of " lime-roasting " of galena as a convenient metallurgical classification,'and this term has found some acceptance. The articles referred to have shown the great practical importance of these new processes, and the general recognition of their metallurgical and commercial value which has already been accorded to them. It is my present purpose to review broadly the changes developed by them in the metallurgy of lead, in which connection it is necessary to refer briefly to the previous state of the art.

Jan 1, 1907

New technology is a significant factor in the present upsurge in world, and Australian, gold extraction and production. The main technologies in current use for gold production are described, referring to overseas developments. Areas where existing techniques have shortcomings or new methods are needed are pinpointed and discussed. Much research work on gold metallurgy is under way round the world, and many new developments have potential. Many of the current research activities round the world are covering unusual and striking areas, with surprising results starting to come through. Some of the "blue sky" techniques reportedly under investigation are identified, together with consideration of when changes in technology are of value. The consequences of new technology for personnel involved in gold plant operations will be raised, including the new education now required.

Jan 1, 1986

By Gordon Revey

In construction and mining work, situations occasionally occur where hard rock or concrete must be excavated at locations near critical structures or utilities. Fearing damage from blasting, contractors and engineers often explore the viability of using mechanical methods or expansive concrete to facilitate the excavation work. However, for moderate to large excavations, the prolonged duration and high cost of using these methods is often impractical. In these situations, under the right conditions, controlled blasting and blast-management methods can be used to speed up the work and lessen costs. The process of determining whether or not blasting is practical is ofien complex, particularly when risks are high.

Jan 1, 2001

By Merete Tangstad, Eli Ringdalen

"In Norway ferrosilicon/silicon and ferromanganese production are strong with world markets of 4 % / 9 % and 4 %, respectively. Research and development in the academia mirrors the national interest; hence, there has been extensive academic research in these areas. There are some vital drivers and premises for a successful cooperation between the academia and industry with the main driver being a win-win situation for both. For industry,the potential advantages include cost-, competence- or environmental- benefits; for academia, the important drivers are building of competence and equipment, educating more students at higher levels, and increased possibilities to publish. In Norway, the benefits of cooperation between industry and academia are basic knowledge regarding thermodynamic and kinetic data, as well as reaction mechanisms within core processes. In recent years, such research interests have focused on the depletion of raw materials as well as environmental issues.IntroductionIn 1989, the Norwegian Ferroalloy Producers Research Association (FFF) was funded on the belief that a common research association would benefit the industry by making it easier to perform basic research as well as paving the ground for better recruitment to the industry. The funding partners in Norway were the FeSi/Si and FeMn producers. Today, the producers are Elkem, Finnfjord, Fesil, Wacker, Eramet and Vale. The main research partners working with FFF are SINTEF (Materials and Chemistry) and the Department of Material Science and Engineering at the Norwegian University of Science and Technology (NTNU). With more than 1700 employees, SINTEF is the largest independent research organization in Norway and NTNU is the largest technical university. Together, the two organizations provide an exceptionally strong materials technology research environment, and especially so for pyrometallurgical research."

Jan 1, 2012

By Joseph L. Margin

From a stubborn start to record setting performances in little over a year, that is the story of the English Running Tunnel Boring Machines. The program to transfer technical information on these highly advanced machines from builder to user will be discussed as a vital link to this accomplishment. Some interesting features of these machines will be covered as well as a recounting of the various conditions that were encountered during these drives and how they were resolved.

Jan 1, 1991

By R. D. Lama

The concept of rigid or yielding bolts is discussed based upon support requirements for excavations of equivalent geomechanical behaviour. The concept of equivalent geomechanical behaviour is introduced for comparison purpose where the rock mass properties are varied for a given depth (stress) so that the deformation of the roof without any support remains constant = 300mm. A simple experimental theoretical analysis for a uniform stress field acting on an axi-symmetric excavation is conducted to establish roof bolt requirements under different conditions such as width of a given excavation, time of setting of support etc. Results are presented in graphical forms.

Jan 1, 1992

By N Barnett, M Dello-lacovo, J Oh, S Saydam, T Pelech

In-Situ Resource Utilisation and Off-Earth mining require the application of horizontal drilling. The stability of such openings is challenging when excavating in the lunar regolith. Excavations on the Moon will encounter unconventional operational conditions such as different material properties, low gravity, and a moonquake. Micro-tunnelling or drilling to support lunar exploration and development of infrastructure on the Moon requires stability analysis to ensure its desired performance. The discrete element method (DEM) modelling technique has been utilised to investigate the optimum opening sizes on the lunar soil. From the literature, the mechanical properties of the lunar regolith have been reviewed and used for numerical model development. The model has been calibrated by simulating numerical triaxial tests with the Mohr–Coulomb failure criterion. Then, detailed parametric studies have been performed to investigate the influence of confinement, opening dimensions and moonquakes on the stability of openings. The findings have led to the development of a simple stability chart of the relationship between unsupported opening sizes and lunar regolith properties at different depths.

Nov 29, 2022

By Brian H. Kaye

Efficient design of grinding circuits for efficient production of ultrafine material requires rapid feedback of information concerning the fineness of material leaving the grinding device Generating this information requires efficient sampling and adequate rapid characterization of the material leaving the grinding machinery Recent developments in electrooptic inspection of dry and wet material leaving a grinding device are critically reviewed New methods for characterizing ultrafines are discussed A rapid operating automated cybernetic (intelligent) permeability device for automatic control of grinding circuits using Blaine Index and other fineness indices is described

Jan 1, 1983

By Sharon Brady, Catherine O’Donoghue, John V. Beall, Paul C. Merritt

Between 1950 and 1965, more than 80% of all phosphate rock produced in the world each year was used as fertilizer, either directly applied to the soil or processed into mixed chemical fertilizers. Of the potassium salts produced, 95% followed suit. A variety of uses in industrial chemicals and consumer products absorbed the remaining percentage of each. Future trends in these two commodities will be dominated by what happens to the fertilizer market. Farming is much the same as mining the soil. Plants remove the minerals little by little. Phosphate and potash comprise two of the three primary nutrients removed in this way, the third being nitrogen. Phosphate stimulates early root formation and growth, whereas potash is a salt necessary to root strength.

Jan 10, 1966

Details are given of the excellent performance, outside Australia, of steel slag in road pavement surfacing. Laboratory tests and plant trials have shown Port Kembla BOF steel slag to be a material with properties suitable for producing asphaltic concrete which will maintain a high skid resistance in service under heavy traffic. The high density of steel slag is a factor which will result in a cartage cost penalty likely to restrict usage to close to its source.

Jan 1, 1979

By Watsford R. M S, Hutton R

Following the delineation of significant extra ore reserves during 1990, the decision was made to expand production from 350,000 tonnes of run of mine ore per year to initially 600,000 tonnes increasing to 750,000 tonnes per year. The existing plant consists of a conventional three stage crushing plant followed by a heavy medium separation plant that produces a product prior to grinding. Grinding is conducted in three stages of ball mill in series. Alternatives examined for expanding production included: aò SAG mill - ball mill circuit replacing the secondary and tertiary stages of crushing, the heavy medium plant and the existing ball mills; and, upgrading of the existing circuit configuration.

Jan 1, 1991