Recently, wet sand blasting on coated cutting tool inserts has drawn interest to the tooling industry due to its positive effects on cutting performance and tool life. This performance boost has partly been attributed to the buildup of compressive residual stresses in the coating during the blasting process. However, the mechanism of forming residual stresses in ceramic coatings during sand blasting is not fully understood. This work utilize x-ray diffraction as the main tool to study the formation and relaxation of residual stresses after wet sand blasting and annealing on 001, 012 and 110 textured α-Al2O3 coatings. To minimize the influence of stress gradients in the samples, all stress measurements were set up with a fixed analysis depth of 2 µm. Sand blasting was made with an alumina based slurry at 2, 3.2 and 4 bar pressure and the anneal was done at temperatures from 400 to 1000 °C for 2 hours or more. The coating hardness was evaluated by nanoindentation. Finally, the activation energy for the relaxation of residual stresses was estimated using the Zener-Wert-Avrami function. The results reveal the highest compressive residual stress with up to -5.3 GPa for the 012 texture while the stresses for the 001 and 110 textures peaked at -3.1 and -2.0 GPa, respectively. Further, a hardness gradient was present after blasting of the 001 and 012 textured samples indicating a higher stress at the surface of the coating. The 110 textured sample is the most brittle resulting in flaking of the coating during sand blasting. The different deformation mechanisms are related to difference in active slip planes between coatings with different textures. Both the stress and hardness decreased after heat treatment and the activation energy for stress relaxation was found to be as 1.1 ± 0.3 eV, 1.9 ± 0.2 eV and 1.2 ± 0.1 eV for the 001, 012 and 110 textures, respectively.

No description available.

Understanding the behavior of geomaterials under explosive loading is essential for several applications in the mining and oil industry. To date, the design of these applications is based almost solely on empirical equations and tabulated data. Optimal designs require accurate and complete knowledge of rock behavior under various loading conditions. The vast majority of the properties available in the literature have been gathered by deforming the specimen slowly. These properties have been used to establish constitutive models which describe the behavior of rocks under static and quasi-static loading conditions. However, the dynamic properties and material constitutive models describing the behavior of geomaterials under high strain-rate loading conditions are essential for a better understanding and enhanced designs of dynamic applications. Some attempts have been made to measure dynamic properties of rocks. Also, some trials have been made to devise material models which describe the behavior of rocks and the evolution of damage in the rock under dynamic loading. Published models were successful in predicting tensile damage and spalling in rocks. However, there are no established models capable of predicting compressional damage in rocks due to dynamic loading. A recently-developed model, the RHT model, was formulated to describe the behavior of concrete over the static and dynamic ranges. The model was also formulated to predict compressional damage based on the strain rate at which the material is subjected to. The RHT model has been used successfully in several applications. The purpose of this research was to characterize one rock type as an example of a hard brittle rock. The physical properties of the rock as well as the static and dynamic mechanical properties were investigated. These properties were used to calibrate the RHT model and investigate its potentials to predict compressional damage in brittle materials. The calibrated model showed good precision reproducing the amplitude of the strain signals generated by explosive loading. It was also capable of predicting compressional damage with acceptable accuracy. Unfortunately, due to implementation restrictions, tensile and spall damage could not be captured by the model. The duration and shape of the strain pulse were also poorly modeled. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2010-12-22 17:54:05.887

Thesis (M.A.)--Ohio University, June, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Orientador: Gilda Carneiro Ferreira / Banca: Elias Carneiro Daitx / Banca: Valdir Costa e Silva / Resumo: Neste estudo foi realizado o monitoramento das vibrações geradas por explosivos em uma lavra de calcário e argilito localizada no município de Limeira (SP), com o objetivo de desenvolver equação probabilística de atenuação de vibração e verificação da existência de variação nos níveis de vibração gerados pelo desmonte em diferentes níveis litológicos e estratigráficos. Os registros da velocidade de vibração de partícula e sua freqüência foram medidos utilizando-se sismógrafos de engenharia, concentrando-se em área localizada a 300 metros a sudoeste do empreendimento mineiro, no Bairro Belinha Ometto. Os trabalhos foram realizados em duas etapas, na primeira foi gerada uma equação probabilística que foi utilizada pela empresa e reduziu os incômodos causados à população pelas operações de detonação. Os valores obtidos na etapa seguinte indicam ser o principal fator na dispersão das velocidades de partícula os desvios nos tempos nominais de retardo dos acessórios de detonação utilizados, tendo como imprópria a elaboração de planos de fogo que contemplem intervalos de tempo nominais entre a detonação de minas ou grupo de minas menores que 25 milisegundos quando da utilização de acessórios de iniciação da coluna de explosivos dotados de tempo de retardo superior a 200 milisegundos. / Abstract: This study performs a ground vibrations monitoring generated by blasting in a calcareous and clay quarry at Limeira city (SP). The main objective is develop a ground vibration attenuation probabilistic equation and verify the existence of vibration levels variation due to the blasting in different lithological and stratigraphical quarry levels. Peak particle registrations and frequency were mesured through engineering seismographs in an area named Bairro Belinha Ometto located 300 meters southwest from the mining site. The data acquisition had been carried through two stages, the first a probabilistic equation used for the company was applied and it reduced the local population disturbs caused by the blasting procedures operations. In the next stage, the obtained values indicate that the deviation in the nominal time delay derived from blasting accessories are the main factor in the dispersion of the resultant particle being therefore improper blasting plans applied in a quarry or a group of them projected with nominal intervals lesser than 25 miliseconds by using in the initiation an explosives column accessories endowed with a delay time superior than 200 miliseconds. / Mestre

M.Sc. / At the very roots of this dissertation lies a commercial process with many as yet unexplored characteristics that will be thoroughly examined, using a rich variety of statistical methods and techniques. Broadly speaking, the main objective of this study involves the development of techniques to control the quality of advanced explosives detonators used in commercial mining operations. To accomplish this task, various statistical characteristics of this detonation process are described and examined in order to obtain a holistic understanding of the underlying process. The parameters of the process are introduced and estimates for unknowns are derived. Real-time quality control techniques based on these results are suggested. 1.2. The role of blasting in mining A major part of South Africa's economy is based on the mining of the rich mineral deposits that are to be found in the country. These mining operations are carried out both above ground (open-pit iron ore mines, for example) and below ground (gold, uranium and others). Open-pit mining, in particular, requires significant amounts of commercial blasting to dislodge the high volumes of material that have to be moved and processed. An average blasting block at Iscor's Sishen mine, for example, contains about 250 000 tons of material, although a world record was established in April 1981 when 7, 2 million tons of rock was broken during a single blast. The chemical quality of the final products is partly controlled by supplying the primary crusher at the mine with a suitable mixture of so-called run-of-mine ore. To determine which material from a specific blasting block may be sent to the plant, and to which waste dump the remaining material should be assigned, factors such as beneficiation properties of the raw material and the content of various by-products are considered. Samples are typically taken from alternate blast holes for every metre drilled. Each drill sample is divided into two parts by means of a riffler for a washed and unwashed sample. The washed samples are examined and the rock types noted. Subsequently, all the samples are grouped and analysed chemically and the densities of the different rock types are determined. The results are processed and those for the washed and unwashed samples correlated. The blasting blocks in the pit are demarcated by means of whitewash lines, according to the divisions on the blasting-block plans, and they are marked with signs to guide shovel operators. Primary drilling is performed by means of electrically-driven rotary drills. At the Sishen mine, 310 mm diameter blast holes are drilled in all rock types. The following table depicts typical drilling 2 patterns for various rock types: Rock type Pattern (m) Drill depth (m) Hard iron ore 2 x 8, 3 3, 0 Medium-hard iron ore 1 x 9, 3 2, 7 Quartzite 8,2 x 9,4 2, 5 Flagstone 8,2 x 9,4 5 Calcrete 8,1 x 9,3 0 Primary blasting is done at Sishen with Heavy Anfo, an explosive that is manufactured by mine personnel at the emulsion plant on site. The ingredients for the explosive blends are transported by pump trucks to the blasting blocks, where it is mixed and pumped down the blast holes. Good fragmentation of the blasted material is a prerequisite for high loading rates by the loading equipment. At Sishen and other similar mines, a blasting efficiency of 3, 2 tons of rock per kilogram of explosives used, is considered to be acceptable.

Overhead conductors used in the transmission of power in grids around the world are generally subjected to ageing, which is the time-based change of their properties. Important properties such as corona discharge, audible noise, hydrophobicity and corrosion are usually considered and investigated. On some conductors such as the aluminium conductor steel reinforced (ACSR), a reduction in audible noise over exposure time to the service environment has been noted to occur. However, the converse has been observed for the gap-type thermal resistant aluminium conductor steel reinforced (GTACSR or “Matthew” conductor), although this conductor is preferred due to its high ampacity. The relationship between conductor hydrophobicity, audible noise, surface contamination and roughness, wettability and corrosion were investigated using All Aluminium Alloy Conductor (AAAC), Aluminium Conductor Composite Core (ACCC) and GTACSR samples. Findings from Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectric Spectroscopy (XPS) and contact angle measurements revealed that carbon, hydrocarbon and silicone contamination was responsible for the hydrophobic nature of the surface. Furthermore, electrochemical investigations and electron microscopy showed that pitting or/and crevice corrosion were the predominant corrosion mechanisms on these conductors. Exposure to simulated industrial and marine environments further confirmed this finding and also showed that general corrosion also occurs on relatively uncontaminated conductors, thereby changing their surface roughness, as seen from the White Light Interferometry results. Corrosion was observed to be accelerated by the presence of surface contaminants such as oils and carbon, as these facilitated water (droplet) retention by reducing the conductor’s surface energy. Reduction/elimination of surface contamination/hydrophobicity were the desired solutions to the problem, and this was achieved by grit blasting. Partial/complete oxidation of the silicones resulted in the reduction/elimination of sample hydrophobicity – this was seen from more contact angles measurements and XPS data. Grit blasting also restored conductor cleanliness and roughened the surface sufficiently to produce surface run-off.

No description available.

Rock slope failures leading to rock falls and rock slides are caused by a multitude of factors, including seismic activity, weathering, frost wedging, groundwater and thermal stressing. Although these causes are generally attributed as separate causes, some of them will often act together to cause rock slope failures. In this work, two of the above factors, seepage of water through cracks and crack propagation due to the after effects of blasting are considered. Their combined impact on the development of rock falls and rock slides is modeled on ANSYS workbench using the Bingham Canyon mine slope failure of 2013 as a case study. Crack path modeling and slope stability analysis are used to show how a combination of crack propagation and seepage of water can lead to weakening of rock slopes and ultimate failure. Based on the work presented here, a simple approach for modeling the development of rock falls and rock slides due to crack propagation and seepage forces is proposed. It is shown how the information from remote sensing images can be used to develop crack propagation paths. The complete scope of this method involves demonstrating the combination of basic remote sensing techniques combined with numerical modeling on ANSYS workbench.