No description available.

No description available.

The accurate determination of wear metals in lubricating fluids is of great potential value in the proper maintainence of all types of machinery. Savings of both time and money have been reported in the military and civilian sectors following the implementation of routine wear metal screening in lubricating oils. Current methods are known to discriminate against metals present in the form of particulates. The first part of this dissertation focusses on the direct determination of wear metals in lubricating oils by atomic emission spectroscopy utilizing an inverted inductively coupled plasma as a source. Data are presented which show the effects of power and viewing position on the signal intensity of a variety of sized iron particulate samples in lubricating oil. The second part of this dissertation describes the characterization of a relatively new spectroscopic source--the dual inductively coupled plasma (DICP). The DICP increases the residence time of the analyte in the source by extending the physical length of the plasma discharge and providing two energy deposition regions. Emission intensity, electron density, ion-to-atom intensity ratios, and calculated temperatures are used to compare the DICP with standard inductively coupled plasmas recorded in the literature.

This study examines decision making concerning tool use and rawmaterial choice through the analysis of bone technology from five sites from the MiddleMissouri subarea of the Northern Plains of North America. The research methods employed include high power optical microwear analysis, experimental replication,and the study of modern bone tool use. At the time of contact with Europeans andEuroamericans, the Mandan, Hidatsa, and Arikara lived in semi sedentary villages along the Missouri River where they practiced a mixed economy centered on both agriculture and bison hunting. The villagers were central in indigenous trade networks and later in the international fur trade, as European and Euroamericans traders and explorers sought to insert themselves into the existing networks. Occasional trade goods are found as early as the seventeenth century, increasing through time as more Europeans and Euroamericans entered the area, indicating that the villagers supplied the newcomers with food, horses, and furs in exchange for those goods. They also were impacted by European diseases, increasing violence, and by accompanying changes in many aspects of their society.Post contact technological change is often modeled as a relatively simple unilinear process in which metal tools quickly replaced older technologies. Analysis of modified bone and antler from historic sites indicates the processes were more complicated. Some tool types were quickly replaced, while others persisted, and there was also variation within tool types. Rather than immediately rendering bone technology obsolete, as has been suggested, there was an initial period of experimentation as people used the new metal cutting and chopping tools to modify the older bone technology. Some tools were made by simply shaping the bone with metal rather than stone, but in other cases the new metal tools were used to create bone tools in completely new forms. Both social and functional factors influence tool choices in raw material, form, and use. This study provides a deeper understanding of many processes involved in technological change in the contact period.

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No description available.

Cutting operations are important and commonly used operations in the field of manufacturing. Automated machining is today commonly used in CNC-machines. One common drawback with automated machining is that the tool condition is challenging to predict which leads to a conservative tool replacement times. This leads to a low utilisation of the tool economical lifetime and an unnecessary high number of tool replacements. Methods for indirect continuous monitoring of the tool wear exist but usually require retrofitting of external sensors that can be both costly and also interrupt the machine operation due to the additional wiring. It is therefore of interest to investigate the possibility to use the, often high resolution, sensors already fitted in a CNC-machine to extract valuable data that can indirectly give an estimation of the tool condition. This thesis work has, with attention to the X-, Y- and Z-position sensors, resulted in development of algorithms that show relations between tool wear and data acquired from these sensors. The algorithms operate in the frequency domain to determine changes in the dynamic response over the time of tool degradation.

This work is a preliminary attempt to study the effect between thermal shock and abrasive wear in WC-Co alloys. This was done by evaluating the thermal shock resistance of a WC-12wt%Co mining grade as a function of temperature, number of thermal shock cycles and making comparisons between the abrasive wear responses of samples subjected to thermal shock and samples not subjected to thermal shock. A furnace was designed for the thermal shock treatments. Abrasive wear tests were performed on a 2-body sliding wear apparatus using 80-grit SiC abrasive paper as a counter-face. Stereo and electron microscopy as well as microprobe techniques were used to analyse the effects of thermal shock. It is confirmed that thermal shock has a negative effect on the wear rate of WC-12wt%Co. The results showed an initial high mass loss rate during abrasive wear testing, which increased with increasing temperature and a decrease in wear rate with time until the wear rates converged for all samples. The surface analysis after thermal shock indicated voids on and below the surface, stained surfaces, a thin oxide layer and the possibility of WC decarburization which accelerated the wear response.

O presente estudo teve como objetivo avaliar quantitativamente a alteração na rugosidade superficial e o desgaste de resinas compostas com diferentes características de matriz orgânica e de carga inorgânica frente ao teste de escovação simulada e ciclagem de pH. Foram testadas três resinas compostas: Filtek Z250 (Bis-GMA, microhíbrida), Filtek Z350 (Bis-GMA, nanoparticulada) e Filtek P90 (silorano, microhíbrida)(3M-ESPE). Para cada resina foram confeccionados dois grupos (n=10) de corpos de prova retangulares (15mmx5mmx4mm). Após a polimerização e polimento adequado dos espécimes, a rugosidade inicial (Ra) foi obtida pela média de três leituras com o Rugosímetro Hommel T1000. Metade de cada corpo de prova foi protegida com esmalte de unha e um dos grupos de cada resina foi submetido a um protocolo de ciclagem de pH (desmineralização-pH 4,3 e remineralização-pH 7,0). Para o teste de abrasão foram realizados 100.000 ciclos de escovação simulada, permanecendo a metade protegida como grupo controle. Na metade escovada foi verificada a rugosidade final, seguindo os mesmos parâmetros iniciais, e o desgaste (µm) foi quantificado pela média de 3 leituras do perfil real abrangendo as duas superfícies (controle e escovada). Os resultados obtidos (ANOVA, teste t Student e Tukey, p<0.05) mostraram diferenças significantes para o desgaste e alteração de rugosidade entre as resinas testadas. A maior média de desgaste foi apresentada pela Filtek P90 (11,505µm±5,690) com diferença significante para a Filtek Z250 (4,191µm±1,725) e para a Filtek Z350 (4,163µm±0,947), sendo que a ciclagem de pH afetou apenas o desgaste da resina Filtek P90 (15,305µm±5,409). Verificou-se aumento da média de rugosidade superficial para as resinas Filtek Z250 e Z350 após escovação simulada, enquanto que a resina Filtek P90 apresentou comportamento contrário, com diferenças estatisticamente significantes (p<0,05). As imagens de microscopia eletrônica de varredura apresentaram-se coerentes com os resultados quantitativos obtidos. / The present study aimed to quantitatively evaluate the surface roughness alteration and wear of resin composites with different characteristics of organic matrix and inorganic filler when submitted to simulated toothbrushing abrasion and pH cycling. Three different resin composites were evaluated: Filtek Z250 (Bis-GMA, microhybrid), Filtek Z350 (Bis-GMA, nanofilled) and Filtek P90 (silorane based, microhybrid) (3M-ESPE). For each resin two groups (n=10) of rectangular specimens (15mmX5mmX4mm) were made. After polymerization and polishing, the initial roughness (Ra) was evaluated by the average of three tracings using a roughness tester Hommel T1000 basic. Half of each specimen was protect with nail varnish and one group of each resin was submitted to pH cycling (demineralization-pH 4,3 and remineralization-pH 7,0). For the abrasion test 100.000 strokes of simulated toothbrushing was processed. The protected side was maintained as control. Over the brushed side the final roughness was measured with the same initial parameters and wear was quantified by the average of 3 readings of the real profile between the two surfaces (control and brushed side). The obtained results (ANOVA, Student t test and Tukey, p<0.05) showed significant differences of wear and surface roughness alteration between the tested materials. Filtek P90 presented the highest average wear rate (11.505 ± 5.690µm) compared to Z250 (4.191 ± 1.725µm) and Z350 (4.163 ± 0.947µm) and the pH cycling significantly affected the wear of Filtek P90(15.305 ± 5.409 mM). The surface roughness evaluation revealed an increasing on surface roughness for Filtek Z250 and Filtek Z350 after toothbrushing, while Filtek P90 showed an opposite behavior, with statistically significant differences (p<0.05). The scanning electron microscope images were in accordance to the quantitative results obtained.

O desgaste em revestimentos refratários é um dos problemas críticos encontrados em ambientes siderúrgicos, que limita a produtividade do processo devido a necessidade de paradas para manutenção nos equipamentos industriais, em favor da substituição do revestimento refratário em regiões desgastadas. Para identificar e caracterizar os mecanismos de desgaste gerados pela ação do banho metal/escória na microestrutura de materiais refratários utilizados como revestimento de panelas de aço de aciaria elétrica, o objetivo deste trabalho foi dividido em três etapas. A primeira etapa é denominada de estudo \"Post-Mortem\", que consiste na amostragem dos tijolos refratários da panela de aço, ao qual foram preparados para análises físico-químicas e microestruturais para a identificação dos mecanismos de desgastes atuantes. A segunda etapa consistiu na preparação dos tijolos novos (mesma composição química dos tijolos post mortem) de maneira a avaliar seu comportamento em relação ao ataque por escória e/ou metal em ensaios termoquímicos e analisar os resultados obtidos com os tijolos \"Post - Mortem\". A terceira etapa foi baseada nos resultados obtidos das investigações das etapas anteriores, ao qual, foram propostos novos tijolos comerciais com diferentes formulações, em parceria com uma indústria brasileira de materiais refratários (Togni refratários), que atenda melhor as exigências das aciarias elétricas. Os resultados que foram apresentados por esta tese, comprovaram que os revestimentos próximos ao ideal, seria os refratários com matriz de cromo (amostra AC_1) e matriz de carbono (amostra AC_2). / Wear on linning refractory is the critical problems found in steelmaking environments, which limits process productivity due to the need for maintenance shutdowns in industrial equipments, in favor of replacing the refractory lining on wear regions. The objective of this work was to identify and characterize the wear mechanisms generated by the action of the metal/slag bath in the microstructure of refractory materials used as coating of steel pans of electric steelmaking, in order to prolong the campaign time of steel pans. This work was divided into three steps. The first step is called a \"Post-Mortem\" study, which consists of the sampling of the refractory bricks of the steel ladle, to which they were prepared for physicochemical and microstructural analyzes to identify the mechanisms of active wear. The second step consisted in the preparation of the new bricks in order to evaluate their behavior in relation to the slag attack in thermochemical tests and to analyze the results obtained with the \"Post - Mortem\" bricks. Based on the results of these initial investigations, new commercial bricks with different formulations were proposed, in partnership with a Brazilian refractory materials industry (Togni refractory), which better meets the requirements of electric steel mills. The results presented by this thesis are innovative and have characteristics in terms of technological contribution in the steel and refractory industries.