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By G. Hu, P. Chang

"As hydraulic fracturing is forbidden in some countries due to its accompanying environmental pollutions, microwave fracturing was proposed as a substitute technology to enhance coal seam permeability. Its mechanism includes: on the one hand, thermal stress caused by non-uniform microwave heating leads to fracture development in coal body, which increases coal seam permeability for gas; on the other hand, moisture within the coal body that hinders gas desorption and diffusion is removed during this process. To study the effect of moisture content on fracture development under microwave irradiation, high resolution photographs were taken before and after microwave treatment. These photographs were then binarized and skeletonized. Based on the processed photographs, the total area were calculated using ImageJ. The results showed that coal samples with 0% and 25% water saturation have more variation in fracture development as compared to that of samples with 50%, 75% and 100% water saturation. This study can be very useful in gas drainage and gas control in coal mines. INTRODUCTION Coalbed methane (CBM) is a clean energy source as well as a natural hazard to underground mining (Kurnia, Sasmito, & Mujumdar, 2014; Ranathunga, Perera, & Ranjith, 2014). One of the main goals of mine ventilation is diluting methane and removing underground contaminants (Xu, Huang, Nie, Chalmers, & Yang, 2017). Coalbed methane (CBM) has to be extracted prior and during underground mining to avoid methane outburst and explosion accidents. However, with the increase of mining depth, the coal permeability decreases significantly, which makes it hard to extract the methane (Huang, Xu, Hu, Kizil, & Chen, 2018). To enhance the coal seam permeability, many CBM recovery methods have been applied on-site, such as hydraulic fracturing and enhanced coalbed methane (ECBM). However, hydraulic fracturing is restricted due to environmental concerns and ECBM is only suitable for the coal seam with relative large permeability (Bustin, Bustin, Chikatamarla, Downey, & Mansoori, 2016; Huang, Xu, Chen, & Chen, 2018; Huang, Xu, Hu, et al., 2018)."

Jan 1, 2019

By Ram Song, Yohei Harada, Shinji Kumai, Kazuho Otsuka

"Recently, vertical-type high-speed twin-roll casting (HSTRC) has been developed. The HSTRC shows extremely high cooling rates over 1,000 K/s even at the mid-thickness area. The fabricated strip has many metallurgical characteristics; super-saturation of alloying elements, fine solidified structure, and homogeneous distribution of fine constituent particles. In Al-Mn based alloys, the Mn alloying element can be supersaturated in the a-Al matrix and also form Mn-containing constituent particles during solidification. The Mn supersaturation and the distribution of primary/secondary particles in cast products affect the metallurgical behavior in the down-stream processing and can improve mechanical properties of the final products. In this study, Al-Mn based alloy strips were fabricated by HSTRC with various Mn contents. The solidified microstructure, constituent particles and its distribution, and Mn solubility were investigated in the as-cast condition. Due to the high cooling rate of HSTRC, fine constituent particles were homogeneously distributed, and coarse intermetallics were not observed. Mn solid solubility was estimated by electrical conductivity. The estimated Mn solubility was equivalent between strip surface and mid-thickness area.INTRODUCTION Al-Mn based alloys, as non-heat treatable wrought aluminum alloys, are widely used in packaging and heat exchanger for automobile industry. Besides Mn, Al-Mn based alloys often contain Fe and/or Si as alloying elements or natural impurities. During solidification, Mn can be super-saturated in the Al matrix, and also form Mn-containing constituent particles. Additionally, in the subsequent thermal-mechanical processes such as homogenization, rolling, and intermediate annealing, Mn in solid solution precipitates out of the Al matrix as secondary particles. The size, distribution, type, and the amount of dispersoids including constituent particles affect to texture evolution, recrystallization behavior, and final mechanical properties of wrought Al-Mn based alloys (Huang et al., 2016; Huang & Marthinsen, 2015; Engler et al., 1995; Muggerud et al., 2013). Therefore, controlling the initial level of Mn super-saturation and the distribution of constituent particles are important in the cast Al-Mn based alloys."

Jan 1, 2018

In order to avoid impurity problem and enhance absorption/desorption kinetics of Mg-based compounds, nanostructured Mg-based compounds were synthesized from Mg, Ni and other elemental nanoparticles produced by hydrogen plasma-metal reaction. XRD and TEM results demonstrate that homogeneous nanostructured Mg-based compounds with less impurity were successfully synthesized by this method. DSC in hydrogen atmosphere, pressure-composition isotherm and the kinetics of hydrogen adsorption/desorption were investigated at different temperatures. The results show that the nanostructured Mg-based compounds can absorb hydrogen in a high speed at a low temperature.

Jan 1, 2005

By V. V. Zubkov

The systems of geophysical monitoring have been already put into operation at coal mines and ore mines. Since at present it is rather difficult to conduct mine experiments; it is necessary to start a new step in joining of geomechanics and seismic. The linking geomechanical and geophysical monitoring at coal mines and ore mines today became possible due to progress in development of numerical methods of modeling of stress state and technology for processing of seismic information. This paper describes one potential step in linking geomechanical and seismic monitoring at coal mines and ore mines.

Aug 1, 2013

By Denis Blackburn

La Direction générale du développement de l?Industrie minérale (DGDIM) du ministère des Ressources naturelles et de la Faune (MRNF) du Québec tient un inventaire de toute l?activité minière sur le territoire. Cet inventaire s?est enrichi, au cours des dernières années, d?un grand nombre de projets dédiés au fer ou à des substances qui y sont associées (titane, vanadium, phosphate). Actuellement, cinq régions du Québec sont principalement touchées par la recrudescence de projets dédiés au fer : Fermont, Schefferville, Baie d?Ungava, Baie-James et Chibougamau. Fermont et Schefferville sont les régions les plus actives. Les infrastructures en place, telles que les routes, les chemins de fer, les ports, les lignes électriques et les municipalités, ont atteint, dans certains cas, leur capacité et de nouvelles infrastructures devront être construites pour satisfaire les besoins. À la Baie-James et sur le flanc ouest de la Baie d?Ungava, des projets d?exploration sont aussi en cours. Le manque d?infrastructure pourrait peser lourd sur le développement de projets miniers dans ces régions. Enfin, dans le secteur Chibougamau/Matagami et à quelques sites ailleurs au Québec, des projets d?exploration qui visent le vanadium, le titane ou le phosphate pourraient aussi fournir comme produit secondaire des concentrés de fer. Tous les projets, décrits dans cet article, sont situés sur le territoire du Plan Nord du gouvernement du Québec.

May 1, 2011

By H. Arima

The Akita Zinc Company is the only refinery which produces hematite from the iron content in the zinc leach residue. The Akita Hematite Process consists of five stages, which are SO2 pressure leaching, the first neutralization stage, the de-arsenic process, the second neutralization stage and pressure hematite precipitation. In order to strengthen its cost competitiveness and stabilize its operation, the Akita Hematite Process has been modified continuously. Most recently, two process modifications were carried out. The first was an improved ability to maintain a lower arsenic concentration in the de-arsenic process, and the second was an increased throughput in the hematite precipitation autoclave. The details of these recent changes in the Akita Hematite Process are presented in this paper.

Jan 1, 2006

By N. W. Xu, M. D. Wei, F. Dai, B. Li

"Chevron notched samples achieve general acceptance for measuring the Mode-I (opening mode) fracture toughness of rocks. The cracked chevron notched semi-circular bending (CCNSCB) sample, which is developed from the International Society of Rock Mechanics suggested the cracked chevron notched Brazilian disc method, has recently received much attention. However, these chevron notched methods have not been fully mastered, some ideal assumptions based by their theories and formulas, such as the straight-through crack assumption (STCA), have not been verified detailedly. Fractures of CCNSCB specimens were numerically simulated considering different heterogeneities, geometrical and mechanical parameters. The results show that, the real fractures of CCNSCB specimens are never satisfied with the STCA. In fact, micro fractures not only occur in the notch tip but also the two chevron edges. Consequently, the crack front features prominently in a shape of parabolic curve, far from being straightthrough. Moreover, curvature of the crack front is only affected by shape of the chevron ligament. Cracks usually start from two sides of the notch tips rather than center of the notch width, and propagate deviating from the postulated fracture routes. These fracture mechanisms induce errors with the measurements, and thus more attentions should be paid to the real fractures of the chevron notched samples for measuring fracture toughness more accurately. INTRODUCTIONWith the increasing requirement of people for resources and energies, frequent rock engineering activities have been conducting, such as underground excavation, oil exploration and deep burial of nuclear waste. Many problems appear in rock fracture. Consequently, there are more and more attentions paid in rock fracture mechanics due to its broad application prospects for solving these engineering problems. Since Mode-I (opening mode) fracture is the most common failure mode in rocks, Mode-I fracture toughness is a primary parameter to predict rock mechanical properties in actual engineering, and thus its accurate values are necessary to the researches of rockburst, rock mass slope stability, rock cutting, hydraulic fracturing, tunneling, et al. Therefore, it is thus significant to evaluate and study relevant methods to obtain the reliable value."

Jan 1, 2015

By A. Moyano

The development of the traditional converting process performed in a PeirceSmith or Hoboken converter is limited by the investment magnitude associated to the fulfillment of the environmental regulations. Thus, the continuous converting process rather than a conceptual process alternative is becoming a necessity for a smelter facing limited converting capacity and/or lacking of fulfillment of the environmental regulation with its maximum converting capacity. The objective of this paper is to present the progress of the Codelco continuous converting process evaluated at pilot-scale level when converting solid mattes or white metal into blister copper. These tests allowed for gathering of relevant data to be considered for a new stage of evaluating the Codelco continuous converting at industrial-scale test. The pilot-scale tests were done in a Teniente Converter pilot scale unit at the Codelco Norte Smelter. The results of processing solid copper mattes (65-75% Cu) and producing low sulfur content blister copper with production of a constant S02 gas concentration, and the production of liquid slag with low copper solubility was achieved and is discussed in the present paper.

Jan 1, 2007

By Nur Hossain

Analysis of Linear Elastic Fracture Mechanics (LEFM) parameters via the Virtual Crack Closure Technique (VCCT) has been obtained for SENT specimens of AM6OB magnesium alloy. It is found that the ratio of initial crack length to initial monotonic plastic zone size is one of the critical factors in establishing the limit of using LEFM concepts. If this ratio is below a certain limit (i.e. when crack lengths are small in comparison to the plastic zone size), loss of similitude stress intensity factor range would occur. This ratio, therefore describes the limit below which the use of LEFM would no longer be admissible. In this study, the above limit was established for AM6OB magnesium alloy. In addition, fatigue crack propagation tests were conducted to ascertain the fatigue response of the alloy and determination of the coefficients of Paris model.

Jan 1, 2010

By J. Gustavsson, S. Holmin, Å. Afvander, E. Rosseland, E. Zimmerman

There are numerous advantages in replacing lead-based anodes with mixed metal oxide (MMO) coated anodes in copper electrowinning; for example, lower energy consumption, improved working conditions for operators and less environmental impact. Since 2012, Permascand AB in Ljungaverk, Sweden has evaluated Permascand coated titanium anodes in copper electrowinning pilot trials at Glencore Nikkelverk in Kristiansand, Norway. The investigation has proceeded in three different steps (Phase I, II and III). In Phase I, different Permascand coatings, electrode structures and coating methods were investigated. The results showed that improved current distribution, lower energy consumption and longer service life could be obtained with expanded mesh electrode structure in a box configuration compared to rod anodes in a single-mode construction. In addition, improved current distribution and less coating wear was found when electrostatic spray coating was used instead of brush (manual) coating. It was also found that the extrapolated service life from controlled lab experiments at 200 A/m2 was much shorter compared to what was experimentally obtained in copper electrowinning pilot trials at similar current densities. This was mainly attributed to different coating failure mechanisms in lab and industrial copper production. INTRODUCTION Traditionally lead-based anodes have been used in copper in electrowinning due to lower cost. But there are many advantages in replacing lead-based anodes with mixed metal oxide (MMO) coated titanium anodes in copper electrowinning, such as lower energy consumption, higher corrosion resistance, improved working conditions for operators and less environmental impact. Still, many facilities are using lead-based anodes, although the progression of using metal oxide coated anodes in copper electrowinning has slightly increased (Robinson et al., 2012).

Jan 1, 2019

By B. Galy, L. Giraud

"This paper compares Canadian provincial mining safety regulations regarding the use and testing of cage safety catches, including a brief history and evolution. Regulations are similar across provinces, with only slight variations. Currently, the “Ontario-type” safety dog is the most commonly used safety catch in Canada. Performance estimation of the compensation mechanism for different safety-dog shapes and tooth angles show this shape works well and has consistent braking results, but the best efficiency is obtained for initial tooth angles greater than 10°. Miner safety is questionable for lightly loaded cages, an issue that should be addressed technically and legislatively.RÉSUMÉ Le présent article compare les diverses réglementations de sécurité minière concernant les parachutes des cages dans les provinces canadiennes ainsi que les essais qu’ils doivent subir. Il semble que les réglementations soient semblables à travers les provinces avec quelques légères différences ou divergences. Un bref historique des parachutes et de leur évolution est présenté. De nos jours, le parachute de « type Ontario » est le plus fréquemment employé à travers le Canada et il présente des résultats de freinage uniformes. Une estimation de la performance du mécanisme de compensation pour les diverses formes de taquets de sécurité et les divers angles des dents montre que cette géométrie fonctionne bien; cependant, la meilleure efficacité est obtenue pour des angles de dents supérieurs à 10°. La sécurité des mineurs est mise en jeu pour des cages faiblement chargées et ce point devrait être traité du point de vue technique et du point de vue législatif."

Jan 1, 2016

By T. Sakai

Present authors have succeeded in single pass large draught rolling of AZ31 and ZK60A magnesium alloy sheets below 200 °C without heating rolls by raising rolling speed above 1000 m/min. Heavy reduction larger than 60% can be applied by single pass high speed rolling even at room temperature. The rolled sheets showed fine recrystallized microstructure by dynamic recrystallization. The improvement of workability at lower rolling temperature is due to temperature rise by plastic working. In high speed rolling, almost all of the work done by plastic deformation is converted into the heat that raises the temperature of the sheet during rolling because the heat did not flow out of the sheet by conduction and radiation within very short time.

Jan 1, 2006

By M. Moats, J. A. Gonzalez

A review of operating practices in zinc electrowinning plants is presented in this paper. Surveys were sent to several zinc electrowinning plants and data provided by some of these plants was compiled in a database. Information about anodes and cathodes, electrolyte composition, stripping methods, cells, electrical systems, and additives was compiled and analyzed. From the data analysis, correlations between operating variables are presented. Recent trends in operational practices are also highlighted.

Jan 1, 2008

By S. Khoshkhooei

In this research, the effects of rare earth elements addition on thermal fatigue behaviors of AZ91 alloy were studied. Repeated heating and cooling cycles were applied on the samples at 170°C and 210 °C to develop thermal fatigue cracks, Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS), Thermal fatigue behaviors were improved successively by addition of up to 2-wt% RE, This improvement is attributed to consummation of the aluminum of the melt by precipitation of the needle shape Al 11 RE3 phases, This process reduces the volume of Mg17Al12 phases and consequently decreases the brittle Mg/Mg17Al12 interfaces which are the main reason of weak thermal properties of the alloy at rather high temperatures, Further additions of RE, however, reduced the thermal shock resistance of samples by increasing in the mean length of the brittle needle shape phases.

Jan 1, 2005

By A. Gakwaya, K. Ba, M. Guillot, J. Levesque

"In the aerospace industry, parts requiring tight dimensional tolerances and high mechanical properties are often produced by forging. This forming process allows for an optimal use of the material and can produce high quality parts at a reasonable cost. Thanks to CAD techniques, it is now easier to predict flow profiles and in-process defects occurrence as well as wear of the forging dies. However, in order to determine the properties of the forged part with computer simulation methods, a good material constitutive law is a prerequisite. This paper presents a virtual manufacturing process modeling for the closed die forging of a workpiece performed with Abaqus. The hot closed die forging is a regular process applied to manufacture metallic components used in aerospace industry. In this forming process, the material flow and final properties depend on the microstructure evolution during the process that is why it is important to include the microstructure effects in the material model. Based on the stress-strain data measured experimentally, the material parameters of the standard (classical) Johnson-Cook constitutive model and of a modified Johnson-Cook constitutive law including the microstructure effects have been determined. The obtained simulation results are compared with the experimental results for validation.INTRODUCTIONDue to their good physical and mechanical properties such as ductility, fatigue strength, corrosion resistance and rupture, aluminium alloys are often used in the aeronautic and the automobile industries. In this work, we present the forging of an Al-Zn-Mg-Cu alloy, a high strength aerospace alloy recognized for his good combination of physical and mechanical properties. The forging process is simulated in Abaqus Explicit using both the standard Johnson-Cook law (Johnson & Cook, 1983; Hor, 2011; Lin et al., 2012), and its modified version as proposed by Andrade et al., (1994). The Johnson-Cook law offers the advantage of considering the coupled effect of the plastic strain, the plastic strain rate, the temperature of forging and the hardening effect. However, it is a phenomenological model which does not account for the effect of the microstructure evolution. In this work, a modified Johnson-Cook model implemented in a user subroutine is used. It includes the effect of the dynamic recrystallization phenomenon during the hot deformation. The dynamic recrystallization has a noticeable influence on the microstructure and on the properties of the material. The term dynamic means that the process starts and acts during the deformation and this is different from the static mechanism of recrystallization which occurs during an annealing and after cold or hot deformation. Since properties of the alloy used in this work are not readily available in the literature then characterization tests have been done at various temperatures and strain rates, in order to determine the thermomechanical properties and the material behavior during the process of hot forming, more precisely during the hot forging process."

Jan 1, 2016

By Guoxiang Chi

This paper consists of two parts: the first part describes the principles and functionality of the BsnMod program, and the second part presents preliminary application of this program to paleo-fluid flow modeling in the Anticosti Basin. The BsnMod program simulates fluid flow and heat transfer during the evolution of sedimentary basins through numerical solution (finite difference method) of three partial differential equations, which describe sediment compaction, fluid continuity, and heat conservation. It can be used to estimate the evolution of fluid overpressure, flow rate, and temperature during the basin history. The program was written in C++, works under Windows environments, and has a user interface allowing inputs in dialogues and outputs in both tabular and graphic forms. The program was applied to the Lower Paleozoic Anticosti Basin in eastern Canada. The basin history consists of a passive margin stage and a foreland basin stage. Preliminary simulation results indicate that no significant fluid overpressures were developed in the passive margin stage and during the early period of the foreland basin stage, but strong overpressures were developed within the foreland basin succession during the middle and late periods of the foreland basin stage. Fluid flow rates were generally slow, and thermal profiles were not significantly disturbed by fluid movement throughout the basin history. Potential source rocks of hydrocarbons were found in the foreland basin succession. The strong overpressures in the foreland basin succession could have been a major driving force for hydrocarbon migration from the source rocks to the underlying potential reservoir rocks.

May 1, 2001

By S. Ando

The fatigue crack growth behavior of magnesium single crystal has been investigated, CT (compact tension) type specimens with different notch orientations were prepared. In the case of notch plane and direction are (1-210) and [10-10], fatigue crack propagates parallel to notch, From TEM observation, it is found that pyramial slips occures at the crack tip. When notch is normal to basal plane, a fatigue crack propagates [0001] and parallel to basal plane depending on stress intensity factor range, In the case of notch parallel to basal plane, a fatigue crack propagates through straight route with some {10-12} twin, Fatigue crack growth rate, da/dN of A- and B- specimen is lower than F-specimen with crack parallel to basal plane.

Jan 1, 2004

By Amir Zavichi

Today, with the necessity of timely, on-budget and high quality completion of projects, proper use of construction equipment is essential to ensure project success. Construction equipment places a large monetary burden on the project and if not utilized efficiently, it can result in economic losses. Cranes are one of the most important and expensive operational devices on construction sites. They play a central role, and often activities that rely on crane services fall on the project?s critical path. Currently, material-handling scheduling is done by the crane operator or by an on-duty superintendent using his/hers personal judgment, making the process manual and timeconsuming. Thus, developing an optimal schedule, which considers different dynamic constraints in construction job site, may not be possible based on the current practice. This leads to longer operation times and a negative impact on project cost. This paper presents the latest results of an ongoing study, which aims to design and implement a nearreal time crane operation decision support system to be utilized directly by the crane operator or as an aid for the superintendent in scheduling optimal operation services. This system has several advantages such as maximizing the efficiency of crane operations, guaranteeing the best operation possible to reduce the crane?s travel time, reducing crews and equipment idle time, and minimizing the dependence on subjective human judgments.

Aug 1, 2013

By C. S. Lord

"The Regal Silver mine is 5 miles north-northwest of Albert canyon; a station on the main line of the Canadian Pacific railway; 21 miles east of Revelstoke; British Columbia.Development, commenced in 1918, comprises more than 8,000 feet of workings from six adits, one of which extends into the Regal Silver property from the adjacent Snowflake ground. Production has been limited to a little tungsten concentrate recovered recently from a few r..undred tons of ore treated in a small underground mill. The property has received some attention as a possible source of tin. The deposits are large quartz veins containing irregular sulphide bodies. Ore minerals normally make up less than 1 per cent of the veins and include pyrite, galena, sphalerite, scheelite, and stannite. The veins are approximately parallel with the bedding of the enclosing graphitic, siliceous to calcareous, slates and argillites. These strata are of Precambrian age, strike about northwest, and dip northeast. No other rocks are known in the vicinity of the workings . Granitic rocks, intrusive into t'he sediments, outcrop 4 miles to the southwest and 7 miles to the northeast and may underlie the property at no great depth."

Jan 1, 1954

By L. Furtenbach, T. Möller

"Grinding mills are the heart of the mineral processing plant, and are production-critical machines which are required to achieve high availability. Liner wear life and a liner design that promotes ease of installation are important variables to achieve a high level of mill availability. Increased mill size results in more mill internal surface to protect, and more liner components to install and remove. This drives designers toward an increase in liner size to minimize the number of components to be installed by the liner handler. The liner attachment method can also have a large impact on mill availability as well as safety during installation.This paper outlines the experience from the development, installation and follow-up of liners installed in two 38' x 45' AG Mills at Boliden Aitik in Sweden. A new Poly-Met shell liner concept has been developed to minimize the number of liner components. The new Poly-Met shell liner components are made much larger than conventional Poly-Met or steel liners. This reduces the number of components to be installed/removed by the liner handler and helps to minimize installation time and consequently down- time. A new attachment system has also been developed to eliminate the need for the installation crew to be in the “drop-zone” of the shell liners while installing the liner bolts.One interesting aspect of this project was the requirement to predict liner life for these new large format AG mills. The existing 22' diameter mills at Aitik provided a base-line reference for this purpose, and DEM studies were used in the project development stage to predict the wear life of shell liners for the new 38' diameter AG mills. The results from this study are included."

Jan 1, 2012