Hypervelocity gouging occurs in high speed sliding systems such as rocket sled test tracks, light gas guns, and railguns. Gouging takes the form of teardrop-shaped craters on the rail surface, and usually only occurs above a threshold speed which is dependent on the slider and rail material properties. In this dissertation, the onset of gouging was studied from three perspectives: application of existing modeling techniques developed for gouging and related fields of research, performing new high-speed experiments using a medium-caliber railgun, and analyzing rail microstructural evolution during gouge onset. A previous gouging model based on shock mechanics was extended, while other models based on mechanisms such as Rayleigh waves, bending waves, and shear band formation were ruled out. An effective Reynolds number approach from explosive welding research was applied to gouging with encouraging results. Based on similarities between gouging, explosive welding, and Kelvin-Helmholtz waves, a linear instability analysis was also performed. A total of 22 railgun experiments were performed to explore different aspects of gouging. Through these experiments, the effect of new slider materials, thin aluminum coatings, and macroscopic rail indentations on the gouging of copper alloy rails were examined. Results using new materials matched the existing models well, though galling damage to copper rails was often as severe as gouging. Gouging was delayed using electroplated aluminum coatings as thin as 2 μm, though this is not necessarily a robust solution. Macroscopic indentations were found to have negligible effect on the threshold velocity for gouging onset, though the morphology of the gouges was strongly affected. Both galling and gouging craters were shown to initiate at existing defects. This applied to both microscopic and macroscopic features. A consistent microscopic feature observed prior to galling and gouging were deformation bands that resembled persistent slip bands on the rail surface. Another consistent feature was the transfer of slider material to the rail prior to galling and gouging. This suggests that gouging may not be triggered by micro-impact events, but by instabilities associated with high-speed thermoplastic shear. / text

A interação entre rocha e metal, na forma de operações como perfuração, escavação e cominuição, dá origem a dois efeitos: um desejado, desagregação da rocha e outro indesejado, desgaste do metal. Como o desgaste, dramaticamente, influencia o desempenho dos equipamentos, é fundamental para estabelecer uma base para equações de predição de taxas de desgaste potencial. Neste contexto, Golovanevskiy e Bearman (2008), propuseram mais um método para avaliação da abrasividade. Este método, ensaio de abrasão por impacto deslizante (Gouging Abrasion Test), é realizado em condições de alta tensão/alto impacto de desgaste e é caracterizado pela maior taxa de remoção de material de todos os modos de desgaste e, portanto, representa o modo mais severo de desgaste abrasivo.O método consiste, basicamente, de uma ponteira cilíndrica com uma ponta cônica de 90º. Esta ponteira, em trajetória pendular, atinge uma amostra de rocha com energia de impacto de aproximadamente 300 joules e velocidade da ordem de 5,2 m/s. Semelhante à metodologia de cálculo de abrasividade Cerchar (CAI), o Gouging Abrasion Index (Gi) é calculado como sendo a média do diâmetro da ponta cônica, após desgaste, em milímetros e multiplicado por 10. Este trabalho verificou a adequabilidade do Gouging Abrasion Test, para um pequeno número de amostras de rocha que representam, qualitativamente, os principais tipos de rocha encontrados no Brasil e a sua correlação com outros ensaios consagrados como resistência à compressão, desgaste Amsler e dureza Knoop. Está análise mostrou alta correlação entre Gi e dureza knoop (R² = 0,94), baixa correlação com desgaste Amsler (R² = 0,41) e nenhuma correlação com resistência à compressão uniaxial. / The rock-metal interaction, like occurs in operations as drilling, excavation and crushing, generates two effects: the desired rock degradation and the undesirable metal wear. As the wear dramatically influences the process performance of the equipment, it is critical to establish a basis for predictive equations to estimate potential wear rates. Following this context, in 2008 Golovanevskiy and Bearman proposed a method for abrasiveness evaluation. The method, Gouging Abrasion Test, employs high-stress load gouging/sliding impact wear and is characterized by the highest material removing rate than all wear modes, therefore representing the most severe type of abrasive wear. The method consists, in a few words, of a steel wear tool with a 90o sharp conical tip. This tip attacks a rock sample in a swinging trajectory with a impact energy of more than 300 joules and a speed around 5,2 m/s. Like the Cerchar Abrasivity Index (CAI) calculation, the Gouging Abrasion Index (Gi) is determined as 10 times de average diameter in millimeters of de conical tip (now flat) after one event of wear. This work intends to improve the knowledge about Gouging Abrasion Test, and evaluates its suitability in a small group of rocks that represents some of the main types to be found in Brazil\'s rock cutting, drilling and crushing works. Its relation to other frequent tests like uniaxial compressive strength, Amsler abrasive wear and Knoop hardness were also verified. The results show high correlation between Gi and Knoop hardness (R2 = 0,94), low correlation with Amsler wear (R2 = 0,41) and no relation to uniaxial compressive strength.

A interação entre rocha e metal, na forma de operações como perfuração, escavação e cominuição, dá origem a dois efeitos: um desejado, desagregação da rocha e outro indesejado, desgaste do metal. Como o desgaste, dramaticamente, influencia o desempenho dos equipamentos, é fundamental para estabelecer uma base para equações de predição de taxas de desgaste potencial. Neste contexto, Golovanevskiy e Bearman (2008), propuseram mais um método para avaliação da abrasividade. Este método, ensaio de abrasão por impacto deslizante (Gouging Abrasion Test), é realizado em condições de alta tensão/alto impacto de desgaste e é caracterizado pela maior taxa de remoção de material de todos os modos de desgaste e, portanto, representa o modo mais severo de desgaste abrasivo.O método consiste, basicamente, de uma ponteira cilíndrica com uma ponta cônica de 90º. Esta ponteira, em trajetória pendular, atinge uma amostra de rocha com energia de impacto de aproximadamente 300 joules e velocidade da ordem de 5,2 m/s. Semelhante à metodologia de cálculo de abrasividade Cerchar (CAI), o Gouging Abrasion Index (Gi) é calculado como sendo a média do diâmetro da ponta cônica, após desgaste, em milímetros e multiplicado por 10. Este trabalho verificou a adequabilidade do Gouging Abrasion Test, para um pequeno número de amostras de rocha que representam, qualitativamente, os principais tipos de rocha encontrados no Brasil e a sua correlação com outros ensaios consagrados como resistência à compressão, desgaste Amsler e dureza Knoop. Está análise mostrou alta correlação entre Gi e dureza knoop (R² = 0,94), baixa correlação com desgaste Amsler (R² = 0,41) e nenhuma correlação com resistência à compressão uniaxial. / The rock-metal interaction, like occurs in operations as drilling, excavation and crushing, generates two effects: the desired rock degradation and the undesirable metal wear. As the wear dramatically influences the process performance of the equipment, it is critical to establish a basis for predictive equations to estimate potential wear rates. Following this context, in 2008 Golovanevskiy and Bearman proposed a method for abrasiveness evaluation. The method, Gouging Abrasion Test, employs high-stress load gouging/sliding impact wear and is characterized by the highest material removing rate than all wear modes, therefore representing the most severe type of abrasive wear. The method consists, in a few words, of a steel wear tool with a 90o sharp conical tip. This tip attacks a rock sample in a swinging trajectory with a impact energy of more than 300 joules and a speed around 5,2 m/s. Like the Cerchar Abrasivity Index (CAI) calculation, the Gouging Abrasion Index (Gi) is determined as 10 times de average diameter in millimeters of de conical tip (now flat) after one event of wear. This work intends to improve the knowledge about Gouging Abrasion Test, and evaluates its suitability in a small group of rocks that represents some of the main types to be found in Brazil\'s rock cutting, drilling and crushing works. Its relation to other frequent tests like uniaxial compressive strength, Amsler abrasive wear and Knoop hardness were also verified. The results show high correlation between Gi and Knoop hardness (R2 = 0,94), low correlation with Amsler wear (R2 = 0,41) and no relation to uniaxial compressive strength.

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The purpose of this thesis is to model the effects of anti-price gouging (APG) legislation on the costs to businesses during the recovery period of a disaster. A system dynamics model of a business’s replenishment procedures is used to simulate the effects of APG legislation on business performance. Economists have published expansive research on the effects of price ceilings on supply and demand, but there is little research evidence on the operational consequences of price ceiling legislation on business costs. APG legislation increases consumer’s forward buying and shortage gaming after a disaster by removing price incentives to be frugal. Forward buying and shortage gaming are two key drivers of the demand variation and the bullwhip effect, which leads to increased inventory costs, misguided capacity expansion and reduced service levels. These costs have a negative impact on local businesses that are critical to a community’s economic health and recovery from a disaster. The simulation results from this thesis show that APG legislation is not an effective regulatory response to decrease the impact of disasters on affected communities.