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In-Situ Leaching (ISL) process plants are low cost producers for uranium deposits where the geology is suitable. In the 1970s, a three-year pilot ISL program occurred on gold ore from the Ajax Mine, Cripple Creek District, Colorado, using a chloride and iodide solution [1]. The test was halted due to poor results. With gold and silver the international ISL progress has been slow; however the potential for low capital expenditure (CAPEX) and operating expenditure (OPEX) with large low grade deposits is real. Unless the metallurgy has been demonstrated there are significant risks which could be fatal flaws to an ISL gold or silver project. The metallurgy of gold ISL projects is far from simple and it is early days with project development.

Jan 1, 2011

By O. S. Perry, G. H. Charlewood, K. Griffin, S Ogryzlo, H. Hopkins, G. MacIntosh

"The gold mines of Kirkland Lake are in Teck township, Timiskaming district, Ontario, latitude 48°9'N. and longitude 80°3'W., at an elevation of 1,038 feet above sea-level.There are seven contiguous producing mines in a length of 3;1/2 miles along the general east-west strike of the deposits. The seven mines are, in order from west to east, Macassa, Kirkland Lake, Teck-Hughes, Lake Shore, Wright-Hargreaves, Sylvanite, and Toburn.The first discovery of gold in the zone was made by W. H. Wright in 1911 on the east claim of the Wright-Hargreaves property, and the following year the Tough brothers and H. Oakes found gold in what is now the No. 1 vein_ at the Toburn. Production began at the Toburn in 1915, followed by Teck-Hughes in 1917, Lake Shore in 1918, Kirkland Lake Gold in 1919, Wright-Hargreaves in 1921, Sylvanite in 1927, and Macassa in 1933.To the end of 1946, 31,938,350 tons of ore had been milled at the Kirkland Lake mines, from which 16,132,700 oz. gold, having a value of $498,517,600, were recovered. The bullion varies from mine to mine between 800 and 900 fine, the average for all the mines being 853. The average fineness of the native gold is 941.The workings of some of the mines are more than 6,000 feet deep and sinking to depths below 7,000 feet is now in progress.GENERAL GEOLOGYThe regional structural geology of the area in which the mines of Kirkland Lake occur is described in a preceding paper in this volume by J. E. Thomson."

Jan 1, 1954

By J. Kronsteiner, E. Kabliman

"In the present work, we developed a Smart Process Control Toolkit (SProC) as a single simulation environment for the modelling of materials microstructure and its interaction with the local microchemistry during manufacturing of semi-finished products. This toolkit supports the data communication between sub-sequent processing steps such as casting, homogenization, pre-heating to deformation, etc. The thermo-kinetical simulation software MatCalc of MatCalc Engineering© GmbH was used for modelling of precipitation kinetics, such as formation of primary and secondary phases and their evolution. An import/export functionality of the precipitation distribution after each processing step was implemented to follow the parameter history. For the evolution of the local microstructure, a Mean Dislocation Density based Model (MD2M) was used. This model consists of two parts: (1) Flow Stress Model for calculation of the total strength during the deformation and (2) Static Recrystallization Model for account of the recrystallization and grain growth after the deformation. Validation was done by a comparison of experimental and simulated hot compression tests of a conventional AA2024 alloy.INTRODUCTION Optimization of a semi-finished products quality, elimination of typical production issues and cost savings are of a great demand for supply industries. However, it is currently not feasible to investigate the whole manufacturing process in detail at an industrial level. Concerning the processing parameters, one must understand the correlation mechanisms between macroscopic properties and microscopic material behavior. Numerical simulations, which could reproduce the real processing conditions on the one hand, and employ a physically based modelling on the other, are thus attracting a lot of attention and their power is no longer under the question. It is well known that e.g. the total strength of the material depends directly on distribution of precipitation particles and mean grain size. In order to follow their evolution during the manufacturing process beginning from casting to the final semi-finished product, and thus be able to control the process, one should use the techniques which would at the same time reproduce experimental processing conditions of real size objects (e.g. sheet, extrusions, etc.) and account for the evolution of a local microstructure and its interaction with the microchemistry. A commonly used approach is to implement a model which would describe the evolution of microstructure based on a dislocation density approach into a user defined material subroutine of some finite element solver. There is, however, also an influence of the manufacturing process by e.g. the evolution of a local microchemistry (formation, transformation and dissolution of the precipitation particles) on the microstructure and thus the macroscopic material behavior. Thus, a method is needed to follow the variable history through the simulation of the whole production chain."

Jan 1, 2018

By L. Fernandes

A two level factorial study was undertaken to investigate the relative impacts of factors affecting the kinetics of polytetrafluoroethylene, PTFE, assisted pressure oxidation of chalcopyrite. A copper flotation concentrate, principally composed of chalcopyrite, was leached in 850 mL of leach solution under conditions similar to those of the CESL process. The factors manipulated were: the amount of 1/8" PTFE beads added (100 g or 650 g), oxygen pressure (690 kPa or 1030 kPa), and concentrate addition (10 grams or 65 grams). Copper extraction data, which indicated complete leaching under certain conditions, were fit using a shrinking core model from which rate constants were estimated and further used to generate a statistical model containing only the factors of significance and their interactions. Results indicated a strong positive effect of PTFE addition and a strong negative effect of increasing pulp density. A weak negative interaction between increasing PTFE addition and pulp density was attributed to PTFE/concentrate agglomeration.

Jan 1, 2014

By G. Morin, G. Marin, M. C. Parr, J. Carignan

"Investment casting offers many advantages for the near net shape production of complex geometries, however, molten titanium reacts with most of the refractories used in investment casting shelling systems, which leads to the formation of an oxygen contaminated surface layer. This layer, called alpha case, is 0.1 to 0.6 millimeters in thickness according to the casting section size and must be removed either by mechanical or chemical milling processes. Alpha case removal processes affect casting tolerances and may contaminate the part intended for medical applications (e.g. embedding of abrasive grit media in the alloy). A shelling system based on an yttria prime slurry has been developed and was found to almost suppress the mold metal reaction. Yttria is an expensive refractory, but slurry life was found acceptable for small castings using a closed container and flow coating process instead of conventional pattern dipping. Alpha case depth has been determined for Ti6Al4V by metallographic techniques and microhardness measurements on different step block casting cross sections. Alumina and yttria second prime stuccos were evaluated in this study. The shelling system minimizes finishing operations in the production of casting for medical applications.INTRODUCTIONTitanium investment castings have been in the commercial market since the beginning of the titanium era in the mid 50’s. Investment casting is a cost effective way to produce complex parts for medical, aerospace and chemical processes applications. Investment casting of titanium is difficult due to the high reactivity of titanium with air and refractories used for shell mold building especially for the face coat. Melting is done under vacuum and no shelling system has been proven effective to suppress the mold-metal reaction yet. The main issue with the mold-metal reaction is the formation of an oxygen enriched zone at the surface of the castings named alpha case (Frueh et al., 1997; Kim, 2002; Saha, 1986). The alpha case is brittle, reduce the fatigue life in service of the parts and must be removed by chemical milling.For industrial purposes, calcia partially stabilized zirconia based slurries have become widely used in titanium investment casting for primary coats due to a combination of limited metal shell reaction. Calcia stabilized zirconia slurries have an acceptable shelf life and offer an interesting production window. Our experience shows that a resulting alpha case depth is 280 micrometers for a casting section of 6.35 mm in thickness is typical with such a shelling system (Morin, 2013)."

Jan 1, 2016

By Euler De Souza

"The uninterrupted operation of a ventilation system is critical to ensure the mine meets its scheduled production and, as important, is vital to the health and safety of all personnel working underground. Those operating the mine ventilation system must have fundamental engineering training in the art of fluid dynamics and have a good comprehension and control of the mine ventilation network. Ventilation management by untrained and inexperienced personnel may result in serious consequences when the system becomes ineffective. This paper shares observations and experiences pertinent to the occurrence of upset conditions as a result of the improper design and operation of mine ventilation systems. A series of real life case studies are presented to describe disruptions to mine ventilation systems and the gradual deterioration of system operational efficiencies leading to eventual failure. Special focus is given to mistakes made and on the resulting serious consequences. The case studies also demonstrate how each upset condition was resolved, permitting the mines to safely resume production activities.INTRODUCTIONThe ventilation of operating mines is a continuously changing and evolving system; upset conditions will occasionally occur, but should be promptly resolved in order for the system to function properly, according to design, and in compliance.Those designing, managing or operating the mine ventilation system must have pertinent training and have a good understanding of fundamental ventilation concepts to be able to devise and implement engineering solutions to day-to-day challenges. Realistically, the operator must also have extensive practical experience and be able to effectively apply operating procedures, design criteria and ‘best practices’. They must be able to, on a daily basis, evaluate the mine ventilation system, determine and locate any problems, understand the causes of each problem, find a solution, and promptly and efficiently correct those problems.Ten case studies are presented to demonstrate how fundamental design or operational mistakes can lead to adverse conditions or to catastrophic consequences, how detailed on-site engineering assessments can be employed and how simple, low cost, engineering solutions can be implemented to successfully resolve the issues and return the ventilation system to compliance, permitting the mines to safely resume production activities."

Jan 1, 2019

By Neil J. Sullivan, Goode. George E.

"The Adams mine, operated by Jones & Laughlin Mining Company, Ltd. and located near Kirkland Lake, Ontario, produces one million tons of iron ore pellets per year. This paper briefly describes the mining and concentrating operation and deals mainly with the operation of the pellet plant. The orebody consists of fine-grained magnetite and some hematite, with alternating layers of chert, and is mined by conventional open-pit methods. After crushing and grinding, the ore is concentrated by magnetic separation and flotation. Agglomeration is accomplished by the grate-kiln pelletizing process. The plant layout and general operation will be discussed in detail."

Jan 1, 1968

By G. Vibert Douglas

"Gold occurs in Nova Scotia in three ways, saddle reefs, fissure veins, and fossil placers. Of these the saddle reefs are the commonest. They have been the source of most of the gold and have also been the subject of most of the literature on the gold occurrences.The Meguma or Gold-bearing series of Nova Scotia is a conformable succession of quartzite's and slates, possibly Precambrian in age, which have been folded into a number of anticlines and synclines that strike (Fig. 1) roughly east and west. This folding has been termed Acadian and is probably a westward continuation of the Caledonian revolution in Britain. It may have started in the Ordovician and continued through the Silurian and into the Lower Devonian. It was followed by the intrusion of the great Devonian granite batholiths. It is thought that the mineralization is connected with the late phases of the cooling of the granite. As the name saddle reef implies, the veins form on the crests and flanks of the anticlines, possibly in the synclinal troughs as well. The beds favoured by the solutions are the slates. The reason for this is apparent when it is realized that in order to fold over 30,000 feet of sediments (the thickness of the Meguma according to E. R. Faribault) through p radians of arc it is necessary to have a differential movement between the top and bottom beds of p times the thickness of the sediments. In the case of the Gold-bearing series, in which strong quartzite beds lie between incompetent slate beds, most of this differential movement was taken up in the slates. The evidence for this is the remarkably fine drag folding and the intense shearing and comminution of some of the beds of slate (Fig. 1). The quartzites exhibit some shearing and faulting, but there is little doubt that the greater permeability lay along the incompetent slate beds. The mineralizing solutions followed these beds and also passed from one slate bed to another through a joint or fault in the intervening bed of quartzite. These joining veins are called angulars in Nova Scotia. Within the veins the gold is in shoots and the real problem is to find out what controls the position and extent of the shoots."

Jan 1, 1954

By X. F. Liu, O. Buzzi, Y. Sieffert

This study falls in the context of underground coal fires (UCF) where burning coal can elevate the temperature of a rock mass in excess of thousand degrees. The objective of the research was to experimentally investigate the change in mechanical behavior of a rock when subjected to temperatures up to 900 °C. Several blocks of an Australian mudstone were collected from a mining site in New South Wales, Australia. X-ray diffraction and thermal-gravimetric analysis were conducted on powdered rock in order to determine the critical temperatures at which the main mineralogical changes occur. Then, cylindrical specimens were prepared from intact rock blocks for unconfined compression tests. These rock specimens were then treated by heating in a temperature-controlled furnace at temperatures varying from 100 °C to 900 °C. The heating process consisted of two stages: raising temperature with very slow rate of 1 °C per hour followed by a holding period of 24 hours and then a slow cooling process to room temperature. The compression tests were carried out on treated rock specimens to characterize the change in compressive strength. The macroscopical study was complemented by microstructural investigations via optical microscope, scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). Results show that the unconfined compressive strength of mudstone decreases with increasing heating temperature up to 450 °C, beyond which it increases. This can be explained by the combined effects of micro cracks and mineral thermal reactions caused by heating process.

Jan 1, 2015

By Cheowchan Leelasukseree

Mae Moh mine, operated by Electricity Generation Authority of Thailand (EGAT), is the largest open pit mine in Southeast Asia. Its production is approximately 15 million lignite tons and 90 million m3 of waste, annually. The bottom of the final pit limit is designed to be approximately 500 m in depth. Presently, the pit depth is almost 250 m below original surface. The complexity of geological structures, such as faults, has caused a number of geotechnical difficulties. In a challenging lowwall area, called Area 4.1, an inclined weak bedding plane, G1, will be daylighted along the lowwall as following by mine plans. The dimensions of Area 4.1 are nearly 300 m wide and 90 m high. The friction and dip angles of the G1 interface are reportedly 12° and 15°, respectively. A three million m3 claystone block, resting above G1, would potentially slide down, and possibly cause a massive failure. EGAT engineers are acutely aware of the potential gigantic sliding failure and are modifying the mine plan in Area 4.1 to improve mine safety and minimize the displacement of the potential sliding block, reduce the possibility of failure and lower the additional mining cost as much as possible. The cut and fill mining technique was selected and studied to achieve those goals for mining in Area 4.1. With this mining technique, G1 will be partially daylighted. Therefore, an arch formation is induced with a sliding block above the mining area, which could perform as a temporary support undercutting a certain span. Initial studies of the behavior of the partially undercut slope are presented in this paper, along with a review of the similar failure history in Mae Moh mine and a 3-dimensional numerical model of the mine. The failure history review provides an estimation of undercut span without failure. The three-dimensional numerical model results, using 3DEC, gave an initial approximation of the displacement of the sliding block in Area 4.1. The next exciting study of the behavior of partially undercut slope is a trial undercut slope field experiment in Area 4.1. Currently, a trial undercut slope field experiment in Area 4.1 is under construction. In the field experiment, a number of monitoring programs will be installed in Area 4.1 to monitor and obtain information to allow a better understanding of the behavior.

Jun 1, 2012

By C. D. M. Chisholm

Introduction The Sullivan orebody is a sulphide replacement deposit in beds of argillaceous quartzites. The general strike of the vein is north and south, with rather an abrupt change to northwest in the north limits, and a pronounced steepening of the dip in the same area. An east-west section across the orebody in the vicinity where the change in strike occurs will show the dip-to the east-to be about 10° to 20° above the 4500 level, 20° to 30° between the 4500 and 3900 levels, and 35° to 45° between the 3900 and 3500 levels. It is this last section, averaging 75 feet in thickness, that is being mined by the blast hole method discussed in this paper. Typically, the mineralization throughout this section follows the same general pattern between footwall and hanging-wall, there being solid sulphides for a width of 30 to 50 feet, above which lie quartzite beds of varying widths separated by ore bands which also vary in width and in grade. This banded part of the vein usually extends for 30 to 40 feet above the solid sulphides, with commercial ore terminating on reaching a siltstone bed. Development is generally carried to the highest ore band which, when averaged with the underlying quartzite band, will assay about the marginal limit in lead and zinc. When wide stopes are opened, sloughing to the siltstone usually occurs and, although the values are too low to carry the cost of developing and mining, the caved muck can be handled profitably with only haulage and treatment to be considered.

Jan 1, 1946

By W. Kempson

"Mining Companies have producing assets in increasingly diverse portions of the world. It is not uncommon that the owner, the design team, the mine contractors and the operators are all based in different countries. While these assets are always subject to the regulatory requirement of those countries there have not been international standards available to review and evaluate these assets. This becomes particularly important when considering safety critical items such as tailings dams, vertical shaft systems and autonomous vehicles to highlight a few. The work currently being completed in ISO ensures these standards will be available and will be generated by and subscribed to on an international basis, thus removing the potential for patriotic partisanship and ensuring safe and predictable systems are installed. This paper will discuss the benefits of the international standards, the structure of the teams and working groups who are generating these standards as well as the process by which the standards are generated. This will allow insight into the creation of the standard and will aim to demonstrate the “neutral” and technically strong manner in which the generation of these standards is achieved. In addition, the paper will discuss the standards which have been produced in the last five years as well as the current standards which are in place. The finale will discuss upcoming work and the timelines in which it is anticipated these will be completed. INTRODUCTION Mining Companies have producing assets in increasingly diverse portions of the world. While these assets are always subject to the regulatory requirement of those countries, there have not been international standards available to review and evaluate these assets. This becomes particularly important when considering safety critical areas such as vertical shaft systems, tailings dams and autonomous vehicles to highlight a couple. The work currently being completed in the International Organization for Standardization (ISO) ensure these standards will be available and will be generated by and subscribed to on an international basis, thus removing the potential for patriotic partisanship and ensuring safe and predictable systems are installed. The ISO/TC 82 – Mining was founded in 1955. This was an active committee until it was thought that the standards at the time were adequate and the Technical Committee was put on “Care and Maintenance”. In 2012 countries lobbied ISO to pull this committee from dormancy and restart it, this happened in in the same year."

Jan 1, 2019

By F. Hassani, J. Peck, D. J. Lucifora

The performance of a rotary blasthole drill is heavily dependent on the material being drilled. This material is a microcosm of the in-situ geology that makes up the surface mine in which the rotary blasthole drill is deployed. The performance metrics that are influenced by the in-situ geology are penetration rate (distance drilled per unit time), rotary torque and to a lesser extent rotary speed and vibration. For simulation and testing purposes it is useful to have a validated plant model based upon the application of study. Once validated, a plant model can be used to perform simulation based testing as a supplement and possibly in place of more expensive and logistically complex field testing. Previous studies in the field of rock mechanics have supplied proven models that relate the performance of a rotary blasthole drill to the material being drilled for a given rock type with a given drill bit. In this study, field based experiments were conducted in an active surface mine on a working rotary blasthole drill and the corresponding monitoring while drilling (MWD) data was recorded. Data analysis was then performed on the collected field data. The techniques used successfully fit the collected MWD data to the previously proven rock mechanic models. This paper explores the theory relating rotary blasthole drill performance to the material being drilled, illustrates the required data collection and data analysis techniques, and demonstrates the ability of these techniques and the known rock mechanic models to provide a simulated plant model for the drilling process that can then be validated. This validation is also discussed.

Jan 1, 2015

By R. Chen, K. Xia

In deep mining activities, blasting induced compressive stress wave would be reflected as tensile wave at a free surface around the openings, which would facilitate the tensile failure of the deep rock since it is much weaker in tension than in compression. It is thus critical to understand the dynamic tensile failure of rocks subjected to static tension for deep rock engineering applications. A modified split Hopkinson pressure bar (SHPB) system is adopted to load Brazilian disc (BD) samples statically, and then exert dynamic load to the sample through stress wave generated by impact. The pulse shaper technique is used to generate a slowly rising stress wave and thus to facilitate the stress equilibrium of samples during each test. Five groups of Laurentian granite (with tensile strength of 12.8 MPa) BD samples under the pretension stress of 0 MPa, 2 MPa, 4 MPa, 8 MPa, and 10 MPa are tested under different loading rates. The result shows that the dynamic tensile strength of the rock decreases with the increase of pre-tension stress, which is easy to understand because pre-tension stress weakens the rock sample. It is also observed that under the same pre-tension stress, the dynamic tensile strength increases with the loading rate, revealing the so-called rate dependency that is common for engineering materials. Furthermore, it is found that the loading rate sensitivity of the rock increases with the increase of pre-tension stress. A qualitative explanation for this phenomenon is that more microcracks are generated and activated under higher pretension stress, resulting in a more viscous material. Based on the results, an empirical equation is proposed to fit the data and explain the dynamic tensile behaviour of rock under pre-tension stress. A physical model is used to simulate the dependency of the dynamic tensile strength of rock on the pre-tension stress and the loading rate, which is shown to be in good agreement with the experimental results.

Jan 1, 2015

By P. Nelson

Extending the campaign life of the Mitsubishi furnaces at Xstrata Copper's Kidd Metallurgical Division Copper Smelter has been a major focus of attention for many years. One aspect of this effort is real time monitoring to detect abnormal conditions and safely shut the furnaces down before significant damage occurs. Traditional real time methods of monitoring the integrity of refractory furnaces containing molten metal include alarms on individual temperatures of the refractory or cooling water. The need to set alarm limits which are not exceeded across the range of normal operating conditions leads to a system that only provides a limited warning, if any, before a failure occurs. Integrity monitoring systems that look at many different signals and alarm only changes in the relationships between the signals have been implemented on the smelting and converting furnaces. The systems are based on principle components analysis (PCA) models and implemented with the monitorMV software package. These provide much more sensitive and selective alarms so that changes in integrity are alarmed well in advance of any event. At a critical alarm level, the converting furnace is set to automatically shut down so that operating and technical personnel can review the situation. The configuration of the systems and operating experience with them will be discussed.

Jan 1, 2007

By I. I. Bethcherman

Introduction 1.-lmportance of Physical Nature of Condensates The metals of commercial interest which have reasonably high vapour pressures below 1,200° C. are mercury, cadmium, sodium, zinc, magnesium, lithium, and calcium. With the exception of mercury, these metals occupy high positions on the electrochemical series and form compounds with very high negative free-energies of formation. It is highly desirable that such metals should not be produced in a form which is finely divided, on account of their reactivity with atmospheric gases. Powders of magnesium, calcium, and even zinc (blue powder) are dangerous to handle and cannot be coalesced by simple melting techniques. Vaporization in vacuo forms a convenient method of handling and purifying the alkaline earth metals in particular and a previous paper by the authors dealt with some of the factors controlling the separation of metals by this technique (12). An essential part of the operation is the condensation of the vapour to produce a massive deposit which may be conveniently melted and handled by established metallurgical techniques. This investigation sought to determine the conditions affecting the nature of solid condensates.

Jan 1, 1951

By Jinsuo Zhang

Investment in coal resource development is affected by a variety of uncertain factors. Investors can make a flexible, strategic decision to achieve the value of risk implicated in those uncertain factors. Therefore, based on real-option theory, we identified key uncertain factors that affect a coal resource investment project, and revealed the formation mechanism of option value in coal resource developing investment project. Then, a multi-factor decision making model was established for a coal resource development investment project with random changes of coal price, interest rate, convenience yield and production cost. Finally, we tested the model and analyzed relevant parameters by applying living data. Our results indicate this model reflects the value of risk implicated in uncertain factors for coal resource development investment, and is able to determine a critical point of decision making change when coal price and production cost varym respectively. By means of parameters analysis, the convenience yield has a positive effect on the project value. The interest rate has a negative effect.

Aug 1, 2013

By Guoxiang Chi

Hydrocarbon fluid inclusions entrapped in diagenetic minerals may be used to constrain hydrocarbon exploration models in two aspects. First, the distribution of different types of hydrocarbon inclusions in different tectonostratigraphic domains, and their relationships with organic matter maturation levels may reflect a regionalscale variation in the thermal regimes of the hydrocarbon systems. Second, the relative timing of hydrocarbon inclusions in the diagenetic history may provide constraints on the evaluation of reservoir potential. This paper summarizes the distribution of hydrocarbon inclusions in four different Paleozoic tectonostratigraphic domains in eastern Canada, discusses its implications on hydrocarbon systems in the different domains, and finally provides two examples to show how the relative timing of hydrocarbon inclusions may be used in the evaluation of reservoir potential. Oil inclusions mainly occur in host rocks that are within the oil zone, although some are found in units in the condensate zone. Light hydrocarbon inclusions occur in the dry gas zone, and methane inclusions were found from dry gas zone to anchimetamorphism zone. This correlation between hydrocarbon inclusions and host rock maturation implies that the hydrocarbons were derived from source rocks having a maturation level broadly similar to the host rocks. Although the Paleozoic rocks are generally relatively poor in reservoir quality, the two examples provided in this paper show that in some stratigraphic units, significant secondary porosities could have existed prior to some hydrocarbon migration events, thus favoring the accumulation of hydrocarbons.

May 1, 2001

By Navid Bahrani

The grain-based model (GBM) has resolved the difficulty of matching both the directtension (sc) and unconfined-compressive (st strengths of typical brittle rock by providing a synthetic material that mimics deformable, breakable polygonal grains cemented along their adjoining sides with deformable, breakable interfaces modeled as smooth-joint contacts. In this paper, a GBM utilizing a parallel-bonded base material is calibrated to match both st and sc of Lac du Bonnet granite and then used to simulate a Brazilian test. The Brazilian strength (sB) is slightly overestimated and the failure mode includes ductile post-peak response that is not representative of what occurs in laboratory Brazilian tests. By reducing the grain tensile strength, grain failure occurs during the Brazilian test and a more realistic failure mode that includes brittle post-peak response is obtained. However, the unconfinedcompressive strength of the modified material is too low. Sensitivity analysis on the grain and grainboundary strength properties demonstrates that the grain tensile strength controls the sB/sc ratio. Because the grain strength is controlled by the parallel-bond properties and the lowest achievable st/sc ratio in a parallel-bonded material is ~0.25, it is concluded thatsc, st and sB for a typical brittle rock cannot be matched with a GBM that utilizes a parallel-bonded base material.

Jun 1, 2012

By J. Fixter, P. Prangnell, Z. Pinter, E. Eimer, B. Chehab

"High deposition rate Wire and Arc Additive Manufacture (WAAM) can provide benefits to the aerospace industry, including a reduction in lead time, reduced material waste and, through higher solidification rates, refinement of the as-built microstructure relative to a cast material. However, candidate 2xxx series high strength alloys for this process normally require a solution treatment, which is problematic for large near-net-shape components, and age hardening to achieve maximum mechanical properties. With each layer being subject to multiple thermal cycles, exploiting the thermal conditions in the WAAM process to avoid post-build solution treatment is therefore of interest. A solutionisation model has been developed for the WAAM process, based on diffusion controlled dissolution using DICTRA, which was validated through thermal simulations combined with 2D and 3D image analysis. The model has subsequently been used to simulate the solutionisation behavior during a typical WAAM thermal cycle and to explore what could theoretically be achieved by, for example, refining the starting microstructure.INTRODUCTION There is currently great interest in exploiting additive manufacturing (AM) in the aerospace sector due to several benefits it can potentially provide; including reduced material waste, shorter product lead times and greater design freedom (Herzog, Seyda, Wycisk, & Emmelmann, 2016). However, with aluminium alloys the material properties obtained are generally inferior to those of conventional high-strength wrought products; therefore more research is required to explore the potential for exploiting the unique process conditions in AM to improve the as-deposited microstructure. A range of AM techniques are now available (Debroy et al., 2018), which differ in terms of the feedstock type and power source and it is necessary to match the appropriate technology to a particular application. This generally requires a compromise between the build rate and shape resolution. Wire and plasma-arc additive manufacturing involves using an electric arc to melt wire onto a substrate, and fabricates a part by building up overlapping layers of deposited weld beads (Addison et al., 2015; Williams et al., 2015). The benefits of this process over other AM methods are the much higher deposition rates (e.g. kg’s/hour) achievable and lower capital equipment costs relative to powder bed techniques, which makes it suitable for large scale applications. However, limitations include a lower part complexity, lower solidification rates and a greater need for post-process machining (Frazier, 2014)."

Jan 1, 2018