Este estudo in vitro teve como objetivo avaliar comparativamente a microdureza superficial e o desgaste de uma resina composta, FiltekTM Z-250 (3M/ESPE), sob influência de diferentes fontes de luz (LED Ultrablue IS - DMC, LED Ultralume 5 - Ultradent e halógena VIP - BISCO), com variação das densidades de potência (300, 600 e acima de 800mW/cm2) e energia (6, >8, 12, >16, 24, >32 J/cm2). Espécimes retangulares (15 x 5 x 4 mm) foram polimerizados, conforme os fatores de variação, totalizando 15 grupos (n=6). Em seguida receberam acabamento e polimento com lixas de abrasividade decrescente (300, 600, 1200 e 2000), sendo armazenados em água deionizada a 37º C por sete dias. As mensurações da microdureza Knoop foram realizadas com auxílio do Microdurômetro Shimadzu HMV-2, com carga estática de 100g por 5s nas superfícies de topo e lateral (50µm da superfície). Posteriormente os espécimes foram levados à máquina de ensaios para simulação de desgaste por escovação, utilizando-se escovas dentais macias (Oral B 30 Indicator) e creme dental (Colgate) diluído em água deionizada na proporção de 1:2 em peso. Ao final de 100.000 ciclos, a dureza da superfície lateral foi novamente mensurada e o desgaste da área escovada foi determinado por meio de perfilometria (Hommel Tester T 1000 basic - Hommelwerke). Os dados de microdureza e desgaste superficial obtidos foram submetidos à análise de variância (ANOVA) e teste de Tukey (p<0,05). Os resultados evidenciaram que a microdureza superficial da resina composta avaliada foi significantemente menor quando da fotoativação com VIP-300 mW/cm2, sendo que os maiores valores foram observados com o aparelho Ultralume 5. O desgaste superficial foi significativamente influenciado quando da utilização de baixa densidade de potência (300 mW/cm2) e energia de 6 J/cm2, tanto com o VIP como Ultrablue IS, que demonstraram maior efetividade quando da utilização de densidade de energia acima de 12J/cm2. De forma geral, observou-se correlação negativa quando da interação dos testes de dureza e desgaste superficial, ou seja, quando os valores de dureza aumentaram os de desgaste diminuíram inferindo, entretanto, que isoladamente o valor de dureza não constitui em parâmetro para qualificar o desempenho da resina composta quanto à resistência ao desgaste. / This in vitro study evaluated comparatively, the superficial microhardness and wear of a resin composite, FiltekTM Z-250 (3M/ESPE) under the influence of different light sources (LED Ultrablue IS/DMC, LED Ultralume 5/Ultradent and halogen VIP/BISCO); with power (300, 600 and above 800mW/cm2) and energy density (6, >8, 12, >16, 24, >32J/cm2) variations. Rectangular specimens (15 x 5 x 4 mm) were polymerized, as the variation factors, totalizing 15 groups (n=6). After, they were ground flat with water-cooled carborundum discs in decreasing abrasive order (300, 600, 1200 and 2000) and stored for seven days, before the tests, in deionized water at 37º C. The Knoop microhardness measurements were carried out using a microhardness tester (Shimadzu HMV-2), with a 100g static load applied for 5s on specimens\' top and lateral surfaces (50µm under surface). In sequence the specimens were taken to a machine for brushing simulation, using soft nylon bristles (Oral B 30 Indicator) and dental paste (Colgate) diluted in deionized water in the ratio of 1:2 in weight. After 100,000 cycles, the hardness of the lateral surface was again measured and the wear profile of the brushed area was determined by a profilometer (Hommel Tester T 100 basic/Hommelwerke). The microhardness and superficial wear data were submitted to the analysis of variance (ANOVA) and Tukey test (p<0.05). The results showed that the superficial microhardness of the evaluated resin composite was significantly lower when photoactivated with VIP-300 mW/cm2, being the biggest values observed for the Ultralume 5 device. The superficial wear was significantly influenced by the low power density (300 mWcm2) and energy density of 6 J/cm2. This was for both, VIP and Ultrablue IS, which demonstrated greater effectiveness when a density of energy above 12J/cm2 was used. In general, a negative correlation was observed between the two tests (wear and microhardness). In other words, there was an increase of hardness with the decrease in wear values, which demonstrates that only microhardness values do not constitute a parameter to qualify resin composite wear resistance behavior.

Hardfacing alloys are utilised in pump and valve components in pressurised water reactors (PWR's). They are designed to withstand wear and galling effects, which occur as a result of surface-to-surface contact, where surface roughness increases by localised plastic deformation, resulting in fracture and material transfer. Typically, alloys that exhibit suitable hardness and galling resistance are known as the Stellites; a Co-base alloy family. Whilst these Co alloys perform well in a hardfacing capacity, they suffer from neutron activation and subsequently decay, forming 60Co isotopes, which emit hazardous γ-rays, contributing to plant worker exposure. The present study was developed to characterise and assess the metallurgical properties of two candidate Co-free replacement alloys; stainless Fe-based alloys Tristelle 5183 and a derivative alloy, developed and patented by Rolls-Royce, known as RR2450. The alloys are produced as gas-atomised powders before undergoing hot isostatic pressing (HIP) into usable parts in-service. As part of this work, we have identified a novel, high-strength Fe-Cr-Ni silicide phase, which precipitates extensively within the RR2450 alloy after HIP consolidation, resulting in the formation of a triplex (austenite/delta- ferrite/silicide) matrix. The use of automated diffraction tomography (ADT) has allowed the crystallography of this phase to be determined as a trigonal R3 space group setting. A carbon atom, identified at a trigonal bipyramidal site along [111] within the silicide phase unit cell, indicates a carbon solubility of up to 1.2 wt% within this phase. HIP cycles were studied in situ using synchrotron X-ray diffraction (XRD), which revealed that the silicide phase decomposes within the metastable gas-atomised RR2450 powder by a eutectoid γ → delta + M7C3 transformation. The starting fraction of metastable delta-ferrite within the RR2450 gas-atomised powder is shown to directly influence the rate of transformation from γ to delta-ferrite during the HIP cycle. The wear resistance of the triplex RR2450 alloy at 300 °C is shown to be superior when compared to the austenitic Tristelle 5183. This is attributed to the high strength silicide phase, which is shown to offer a hardness up to 2 to 2.5 times greater than the austenite and delta-ferrite phases. By producing an elastic angular distortion of the unit cell, the silicide phase is able to withstand loading up to 1 GPa without yielding. The Tristelle 5183 alloy, which produces a lower fraction of silicide phase compared to RR2450, is reliant on the formation of stacking faults and a strain induced martensitic transformation to provide a high wear resistance. These transformations are shown to reduce substantially during wear testing at 190 °C, leading to a loss of high temperature wear resistance in the Tristelle 5183 alloy. Future work into developing silicide based Fe hardfacings is suggested, the microstructures of which can be tailored by controlling Si and Ni additions.

The annual cost of corrosion in the United States Navy and Coast Guard is in excess of $2.7 billion dollars. The salt water environment provides a ripe surrounding for rapid corrosion and deterioration of ship decking, which requires frequent and expensive maintenance. Decks of ships are susceptible to corrosion and wear, but must also maintain a non-slip surface in a constantly wet environment. Few options for non-skid deck materials are currently approved for use by the Navy and require frequent and expensive maintenance or replacement. A new material known as Laser Deposited Non-Skid, currently used in industrial flooring applications, shows potential for serving as a more durable non-skid material with extended service life and greater resistance to corrosion. The purpose of this research is to investigate the feasibility of Laser Deposited Non-Skid in decks of ships and to compare the corrosion, wear and cost data with existing deck materials. Sample plates of A36 and A572 steel and 5086 and 5456 marine grade aluminum alloy were coated with selected non-skid materials and subjected to laboratory salt fog testing and corrosion in environmental conditions in the Caribbean Sea. Wear behavior among non-skid materials was evaluated through wear cycles, measurement of coefficient of friction, and surface characterization. Salt fog testing was more corrosive than the actual operational environment in all cases and the Laser Deposited Non-Skid samples had the best resistance to wear and corrosion. The Peel and Stick Non-Skid demonstrated corrosion by undercutting while the Traditional Non-Skid corroded through the material. The relative area did not correlate well with friction or wear mass loss. Aluminum Laser Deposited Non-Skid appears suitable for use as a deck material on small boats. More research is needed to evaluate maintenance issues and possible stress cracking associated with the Laser Deposited Non-Skid on steel decks.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / Ph.D.

Devant le succès maintenant bien démontré des prothèses totales de hanche, les chirurgiens sont amenés à proposer ce traitement chez des patients dont l’espérance de vie ne cesse d’augmenter. Parallèlement, une population plus jeune et active a aussi recours à ce traitement permettant de reprendre rapidement ses activités professionnelles et de loisirs. Des progrès exceptionnels ont été réalisés par les bio-ingénieurs en collaboration avec les chirurgiens dans la production industrielle d’implants en polyéthylène désormais très performants avec des taux d’usure très faibles. Néanmoins, bien que très diminuée, cette usure aboutit à la production de particules micrométriques libérées autour de la prothèse. Ces particules d’usure interagissent avec les tissus environnants et notamment les macrophages circulants, conduisant à une réaction inflammatoire. Les macrophages, cellules clés de cette cascade inflammatoire, subissent une activation par phagocytose ou par contact membranaire avec les particules puis une polarisation engendrant la libération de molécules à fort pouvoir inflammatoire : cytokines, chemokines, dérivés oxygénés, TNF-α et autres conduisant au maintien d’un niveau inflammatoire élevé autour de la prothèse. A long terme, le risque est l’évolution vers l’ostéolyse péri-prothétique et le descellement aseptique dont le seul traitement est la reprise chirurgicale, intervention difficile chez des patients qui ont vieilli. La compréhension des mécanismes biologiques de cette réaction inflammatoire permet le développement de stratégies modulant ou inversant cette inflammation afin d’augmenter la longévité des prothèses totales de hanche. / Total hip replacements are now very succesful and surgeons perform this procedure in patients with an increasing longevity. Young and active patients are also candidates for this surgery allowing them to quickly resume their professional and recreational activities. Exceptional advances have been made by bio-engineers and surgeons in the production of highly efficient polyethylene implants which have very low wear rates. Nevertheless, wear remains and wear particles are still released around the implant. These particles react with the surrounding tissues especially macrophages, leading to an inflammatory reaction. Macrophages are then activated and subsequently polarize releasing inflammatory factors such as cytokines, chemokines, oxide species and TNF-?. This could lead peri-prosthetic osteolysis and aseptic loosening requiring revision surgery, a difficult procedure. Understanding the biological mecanisms of this inflammatory reaction may help creating strategies to mitigate or reverse this inflammation with the goal to increase the longevity of these implants.

Doctor of Philosophy / The drastic improvements in stiffness and strength even with the addition of small percentage of clay to a polymer are commonly traded-off with significant reductions in fracture toughness. It is believed that the presence of a stiff nano-filler will restrict the mobility of the surrounding matrix chains, and thus limit its ability to undergo plastic deformation, thereby decreasing their fracture toughness. To understand the role of rigid nano-fillers, like clay and their constraint effect on the surrounding polymer matrix, the effects of preferentially organized polyamide 6 lamellae in the vicinity of organoclay layers on the toughening processes are studied and compared with polyamide 6 filled with an elastomeric additive (POE-g-MA). It is suggested that to impart high toughness to polymer/organoclay nanocomposites, full debonding at the polymer-organoclay interface is necessary so that shear yielding of large volumes of matrix material can be enhanced. However, due to the strong tethering junctions between the individual organoclay layers and the matrix, full-scale debonding at the polymer-organoclay interface is rarely observed under stress conditions indicating that the constraint on the polymer adjacent to the clay is not relieved. Therefore, this has led to the development of ternary nanocomposites by adding a soft elastomeric dispersed phase to polymer/clay systems to obtain well-balanced mechanical properties. Polyamide 66/SEBS-g-MA/organoclay nanocomposites are prepared with four different blending protocols to understand the effect of blending protocol on the microstructure, mechanical properties and fracture mechanisms of the ternary nanocomposites so as to obtain new insights for producing better toughened polymer nanocomposites. In general, it is found that the level of enhancement of fracture toughness of ternary nanocomposites depends on: (i) the location and extent of dispersion of organoclay and (ii) the internal cavitation of rubber particles leading to effective relief of crack-tip tri-axial constraint and thus activating the matrix plastic deformation. Based on the wear/scratch damage studies on different polymer nanocomposite systems, it is suggested that elastic modulus and toughness of polymer nanocomposites are not the predominant factors controlling the material removal or friction coefficient and cannot be the sole indicators to compare and rank candidate materials. It is also found that nano-fillers by themselves, even if uniformly dispersed with good interfacial interaction with the matrix, do not irrevocably improve the wear (and friction) properties. Although it is important to consider these factors, it is necessary to thoroughly understand all microstructural parameters and their response to wear/scratch damage. Other important factors that should be considered are the formation of a uniform and stable transfer film on the counterface slider and the role of excessive organic surfactants or other modifiers added to disperse nanoparticles in a polymer matrix. It is also emphasized that the mechanisms of removal of materials during the wearing/scratching process should be studied meticulously with the use of high resolution microscopic and other analytical tools as this knowledge is critical to understand the surface integrity of polymer nanocomposites.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 82 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 74-75).

Thesis (Ph. D.)--Oregon Graduate Center, 1982.

This thesis is a use-wear study that deals with microwear on stone endscrapers used on one worked material: animal skins. The first part of the study defines and describes the process of rendering freshly skinned pelts into functional leather or rawhide products, addressing confusing terminology found in the literature as well. Problems with past use-wear experiments dealing with animal skins are also confronted and explained. The second part of the study examines endscrapers used to flesh and dehair bison hides and compares the use-wear traces left on the tool edge by each activity. This suite of characteristics is then compared to those found on an assemblage of Clovis-age scrapers from the Gault site in central Texas.

A general approach to numerically simulating wear in rollingand sliding contacts is presented in this thesis. A simulationscheme is developed that calculates the wear at a detailedlevel. The removal of material follows Archard’s wear law,which states that the reduction of volume is linearlyproportional to the sliding distance, the normal load and thewear coefficient. The target application is the wheel-railcontact. Careful attention is paid to stress properties in the normaldirection of the contact. A Winkler method is used to calculatethe normal pressure. The model is calibrated either withresults from Finite Element simulations (which can include aplastic material model) or a linear-elastic contact model. Thetangential tractions and the sliding distances are calculatedusing a method that incorporates the effect of rigid bodymotion and tangential deformations in the contact zone.Kalker’s Fastsim code is used to validate the tangentialcalculation method. Results of three different sorts ofexperiments (full-scale, pin-on-disc and disc-on-disc) wereused to establish the wear and friction coefficients underdifferent operating conditions. The experimental results show that the sliding velocity andcontact pressure in the contact situation strongly influencethe wear coefficient. For the disc-on-disc simulation, therewas good agreement between experimental results and thesimulation in terms of wear and rolling friction underdifferent operating conditions. Good agreement was alsoobtained in regard to form change of the rollers. In thefull-scale simulations, a two-point contact was analysed wherethe differences between the contacts on rail-head to wheeltread and rail edge to wheel flange can be attributed primarilyto the relative velocity differences in regard to bothmagnitude and direction. Good qualitative agreement was foundbetween the simulated wear rate and the full-scale test resultsat different contact conditions. <b>Keywords:</b>railway rail, disc-on-disc, pin-on-disc,Archard, wear simulation, Winkler, rolling, sliding