Les difficultés majeures rencontrées en production des pièces mécaniques métalliques sont dues aux conditions de chargements extrêmes appliqués lors de la mise en forme ainsi qu'au problème de l'usure prématurée des outils de coupe de coupe. Dans ce cadre, les travaux de thèse sont centrés sur la mise en évidence et la compréhension des mécanismes physiques mis en jeu lors de l'usure des outils de coupe depuis l'échelle de la microstructure jusqu'à celle du système usinant, en passant par l'échelle de la pointe de l'outil (échelle mésoscopique). A cet effet, Un modèle analytique permettant de décrire l'usure par abrasion et de prédire la durée de vie des outils a été développé sur la base d'une approche statistique rendant compte de l'hétérogénéité des particules pouvant être à l'origine de la dégradation de l'outil. La prise en compte de la nature du contact collant-glissant et de l'effet du coefficient de frottement via des résultats de la littérature couplés au modèle proposé ont permis de mettre en évidence l'influence des paramètres opératoires de la coupe des métaux sur le volume d'usure enlevé par abrasion. A la suite ce modèle a été confronté à des résultats expérimentaux préalablement réalisé dans le cadre de la coupe orthogonale. En parallèle une analyse inclusionnaire est réalisée pour l'identification et la quantification des inclusions non métallique jugées responsable de l'usure par abrasion. Les résultats obtenue via des observations MEB et microscopique ainsi que des traitements d'images a permis d'alimenter en données le modèle prédictif / Tool wear and tool failure are critical problems in the industrial manufacturing field since they affect the quality of the machined workpiece (unexpected surface finish or dimensional tolerance) and raise the production cost. Improving our knowledge of wear mechanisms and capabilities of wear prediction are therefore of great importance in machining. The three main wear modes usually identified at the tool/chip and the tool/workpiece interfaces are abrasion, adhesion and diffusion. Besides the fact that understanding mechanisms that govern these wear mechanisms are still incomplete, the experimental analysis is very difficult because friction interface features (such as temperature, pressure, particles embedded in the contact …) are not easily measurable. The objective of this research work is to understand the physical mechanisms governing the tool wear by taking into account the sensibilities to scale going from the microscopic scale (microstructure scale) to the macroscopic scale (scale of the manufacturing operation) passing by the mesoscopic scale (tool tip scale). For this purpose, an analytic wear model was developed to describe the abrasive wear and to predict the cutting tool life. The proposed model is based on a tribological approach including a statistical description of the distribution of particles seen as non-metallic inclusions. The latter are assumed embedded at the interface of contact and having a conical shape characterized by two main parameters in the present approach: the corresponding size and apex angle. The volume of the removed material per unit time is chosen in this study as the main parameter to describe the abrasive wear mode. Coupled with literature results, the developed model is able to take into account the nature of the sticking-sliding contact and the effect of the friction coefficient on the rake face of the cutting tool. In order to identify all the material's parameters of the predictive model, a study of non-metallic inclusion considered responsible of the abrasive wear was performed on the 42CD4 steel. The determination of inclusion type and inclusion morphology was assessed qualitatively and quantitatively through microscopic and MEB observations as well as image processing. Finally, the volume removed by abrasion given by the model was compared to the experimental results previously achieved under orthogonal cutting.

This diploma thesis deals with concrete abrasion resistance against abrasion. The constructions of transport and water management structures are most stressed by the action of abrasion by means of travel of vehicles and flowing water. Abrasion reduces the durability of the structures. The prerequisites for achieving the best possible abrasion resistance are examined. Furthermore, test methods that are currently used worldwide. The experimental part deals with the influence of individual types of aggregates amphibolite (Želešice), fecal gravel sand (Žabčice) and basalt (Bílčice) on abrasion resistance. Furthermore, the dependence between the strength of the concrete and the hardness of the surface for abrasion resistance. Abrasion resistance testing was determined by concrete abrasion, abrasion resistance by the Böhm method and by water jet.

High-temperature abrasion is an expensive issue in industrial fields such as glass and cement production or mining and processing industry. Yet its effects on steel are not well documented. This study investigates and analyses the behaviour of six different steel grades placed in hot abrasive conditions similar conditions encountered in the industry to enables better material selection.  Abrasion tests in a slurry pot were done at room temperature and at 500 °C. Impact and tensile tests were also performed at different temperatures. To complete the mechanical properties evaluation, hardness measurements were executed before and after tempering at 500  °C. Wear rates assessed at room temperature or at 500 °C, are independent of the mechanical properties of the material. At high temperature, it was shown that wear rates and performance of the steels were influenced by tempering and leading to a unique microstructures for all steel grades investigated and equalize their performances. To conclude, high temperature wear of the investigated grades does not depend on their mechanical properties, however, it can be influenced by their tempering resistance. As the temperature increase, steel tempers, its mechanical properties decrease and homogenise with other steel grades' performances, but some grades keep their properties longer at high temperature.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Toothpaste abrasivity is considered the major contributor in toothbrushing abrasive wear, while toothbrush stiffness can be considered a secondary factor that may modify the abrasivity of toothpaste. Objectives: To investigate the longitudinal enamel and dentin surface loss caused by the interaction between the abrasives in toothpaste and toothbrush filament stiffness. Study Hypothesis: The amount of enamel and dentin loss depends on the abrasivity of the toothpaste and the filament stiffness of toothbrush. Materials and Methods: The following experimental factors were considered: abrasive suspension, at two levels (L-low: Z113 and H-high: Z103); and toothbrushes at three levels determined by bristle stiffness (soft, medium, and hard) generating 6 testing groups (n = 8). Slabs of bovine enamel and dentin were cut, embedded in acrylic resin, and polished. UPVC tapes were placed on the surface of the specimens, leaving an area of 1 × 4 mm exposed in the center of the each enamel slab. Specimens (n = 8) were subjected to 5 d of erosion/abrasion cycling: erosion (5min, 4×/d, 0.3% citric acid, pH 3.75), abrasion (15 s, 2×/d, 45 strokes each, 150-g load, automated brushing machine), fluoride treatment (15 s with abrasion and 45 s without abrasion; 275 ppm F as NaF in abrasive slurry) with exposure to artificial saliva between erosion and abrasion (1h) and all other times (overnight). Surface loss (SL, in micrometers) was determined by optical profilometry, after the third and fifth days of cycling. Data were analyzed using three-way ANOVA (alpha = 0.05). For enamel, only cycling time was found to affect surface loss with 5 d > 3 d. Overall, there was little SL (mean range: 0.76 µm to 1.85 µm). For dentin (mean SL range: 1.87 µm to 5.91 µm), significantly higher SL was found for 5 d vs. 3 d, with particularly large differences for hard toothbrush high abrasive, and medium toothbrush/low abrasive. Hard toothbrush resulted in significantly higher SL than medium toothbrush for high abrasive after 5 d, with no other significant stiffness differences. High abrasive had significantly higher SL than low abrasive overall with strong effects for all combinations, except medium stiffness after 5 d. In conclusion, the interplay between abrasivity and filament stiffness appears to be more relevant for dentin than enamel.

SammanfattningSyfteSyftet med föreliggande pilotstudie är att undersöka abrasion på materialen polerad zirkonia (5YSZ) och glansbränd litiumdisilikat och abrasion på antagonist med eller utan termocykling. Emalj utgör referens. De inkluderade materialen är avsedda för CAD/CAM- framställning av monolitiska konstruktioner.Material och metodFrån en zirkoniadisk (5YSZ, Katana zirconia UTML) och tre litiumdisilikatblock (IPS e.max CAD LT) togs totalt sexton provkroppar fram. Åtta extraherade molarer användes som referensgrupp (n=8) och steatitkulor användes som antagonist. Provkropparna för zirkonia och litiumdisilikat utformades rektangulära med måtten 16x14x3,5 mm efter sintring respektive kristallisering. Provkropparnas testytor genomgick olika ytbehandlingar. Zirkoniaprovkropparna polerades till högglans (ZP), litiumdisilikat glansbrändes med glaze (LG) och de extraherade molarerna planslipades och emaljen polerades (EM). Hälften av materialgrupperna tuggsimulerades i 120 000 cyklar med termocykling i temperaturerna 15°C±2°C respektive 55°C±2°C (ZPT, LGT, EMT). Den andra hälften tuggsimulerades i 120 000 cyklar utan termocykling (ZPU, LGU, EMU). Resultaten analyserades med One-way ANOVA, Tukey’s test med en signifikansnivå på α=0,05 i statistikprogrammet SPSS.ResultatHögst materialförlust påvisades i EMT-gruppen och lägst i ZPU-gruppen. Ingen signifikant skillnad kunde påvisas mellan materialgrupperna. Hos antagonistgrupperna påvisade EMT- gruppen högst materialförlust och LGT-gruppen lägst materialförlust. Hos antagonistgrupperna hade EMT-gruppen en signifikant högre materialförlust i jämförelse med övriga antagonistgrupper förutom LGU- och ZPU-gruppen.SlutsatsPolerad ultratranslucent zirkonia, glansbränd litiumdisilikat, och emalj abraderas likvärdigt av antagonister med eller utan termocykling. Polerad ultratranslucent zirkonia och glansbränd litiumdisilikat abraderar mindre mot antagonister än emalj med termocykling. / AbstractPurposeThe purpose of this pilot study is to investigate the abrasion of polished zirconia (5YSZ) and glazed lithium disilicate on antagonist and antagonists’ abrasion on the materials with or without thermocycling, with enamel as reference. The materials are intended for CAD/CAM production of monolithic restorations.Material and methodFrom zirconia (5YSZ, Katana zirconia UTML) and lithium disilicate (IPS e.max CAD LT) sixteen specimens were made. Eight extracted molars were used as reference group (n=8) and steatite balls used as antagonists. The specimens were designed with the dimensions 16x14x3.5 mm. The zirconia specimens were polished to high gloss (ZP), the lithium disilicate glazed (LG) and the enamel ground flat and polished (EM). Half of the groups underwent chewing simulation in 120,000 cycles with thermocycling (15°C ±2°C/55°C ±2°C) (ZPT, LGT, EMT) and the other half without thermocycling (ZPU, LGU, EMU). The results were analyzed with One-way ANOVA, Tukey's test with a significance level of α= 0.05 in the statistical program SPSS.ResultsThe highest material loss was in EMT and the lowest in ZPU. No significant differences could be shown between the material groups. In the antagonist groups, EMT showed the highest material loss and LGT the lowest. In the antagonist groups, EMT had a significant higher loss in comparison with all the other antagonist groups except LGU and ZPU.ConclusionPolished ultratranslucent zirconia, glazed lithium disilicate and enamel are equally abraded by antagonists with or without thermocycling. Polished ultratranslucent zirconia and glazed lithium disilicate abrade less against antagonists than enamel with thermocycling.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

AB SOMAS Ventiler manufactures valves for different applications. A valve of type DN VSSL 400, PN 100, used in high-temperature and high-pressure applications was investigated in this thesis. This type of valve is coated with high cobalt alloys to achieve the tribological properties needed for this severe condition. However there is a request from AB Somas Ventiler to find another solution. This request is based on the fact that demands on higher temperatures, from customers, yields higher requirements on the material. It is also a price issue since cobalt is quite expensive. Materials investigated were high-nitrogen steel, Vanax 75, nickel-based superalloy Inconel 718 and hardened steels, EN 1.4903 and EN 1.4923 presently used as base material in the valve. Calculation of contact pressure that arises when the valve is closed was first approached by using finite element method (FEM). Several models were constructed to show the behavior of the valve during closing in terms of deformation. Hot wear tests, in which a specimen was pressed against a rotating cylinder, were performed to be able to compare the materials to the solution of today and among each other. Data extracted from the tests were compiled in the form of coefficients of friction. Profilometer examinations were used to reveal the volumes of worn and adhered material and together with scanning electron microscopy (SEM) the wear situation for each material couple could be assessed. Wear mechanisms detected in SEM were adhesive and abrasive and the results clearly showed that the steels were not a good solution because of severe adhesive wear due to the similarity of mating materials creating a more efficient bonding between the asperities. Vanax 75 showed much better performance but there was still an obvious difference between the steels and the superalloy in terms of both coefficient of friction and amount of wear. On this basis, Inconel 718 was selected as the most suitable material to replace the high cobalt alloys used in the valves today. / AB Somas ventiler är ett företag som tillverkar ventiler för ett brett spann av applikationer. I det här examensarbetet har undersökningar genomförts på en ventil av modell DN VSSL 400, PN 100, som normalt används i applikationer för höga tryck och höga temperaturer. Ventilen beläggs i dagsläget med höghaltiga koboltlegeringar för att uppnå de tribologiska egenskaper som krävs i de påfrestande arbetsförhållanden som råder. AB Somas Ventiler har dock framfört en förfrågan om att hitta en alternativ lösning, en förfrågan som grundar sig i att kundernas ständiga önskemål på att ventilerna ska klara högre arbetstemperaturer också medför högre krav på ventilmaterialen. Det är även en prisfråga, då kobolt är en dyr legering att använda sig av. De material som inkluderades i undersökningen var det kvävelegerade stålet Vanax 75, nickelbaserade superlegeringen Inconel 718 samt de två stålen EN 1.4903 och EN 1.4923 i härdat tillstånd. De två sistnämnda används idag som basmaterial i ventilen. Genom att använda den finita element metoden (FEM) kunde en första beräkning göras av det kontakttryck som uppstår då ventilen stängs. Flera modeller konstruerades för att simulera ventilens deformation vid stängning. Där efter utfördes nötningstester i hög temperatur på de alternativa materialen, genom att låta en provbit pressas mot en roterande cylinder, för att sedan kunna göra en jämförelse mellan materialen och även med den nuvarande lösningen. Från nötningstesterna erhölls data som kunde användas för att ta fram friktionskoefficienter för de olika materialparen. Med hjälp av undersökningar med profilometer och svepelektronmikroskop (SEM) kunde värden på nötta och vidhäfta volymer erhållas tillsammans med information om nötningssituationer för ytorna mellan de olika materialparen. De nötningsmekanismer som påvisades med hjälp av SEM-undersökningen var adhesiv och abrasiv nötning, och resultaten visade tydligt att nötningen av stålen var omfattande, på grund av att lika material i kontakt med varandra skapar starkare band mellan ytorna, och att de därför inte var en intressant lösning. Det kvävelegerade Vanax 75 uppförde sig visserligen bättre men en tydlig skillnad mot superlegeringarna kunde dock fortfarande konstateras, sett till både friktionskoefficient och mängden slitage. Baserat på dessa resultat valdes Inconel 718 som det bäst lämpade materialet att ersätta de höghaltiga koboltlegeringarna som idag används i ventilen.

The interest in superhydrophobic coatings have increased exponentially in the recentdecades due to their potential and versatility in their applications. The use forsuperhydrophobic surfaces range from water repellent fabric, to self cleaning surfacesand numerous applications in industry. In this project the durability of 6 differentsuperhydrophobic coatings have been examined. The durability was tested bydropping sand on the surfaces from a set hight of 10 cm and a flow of 40 g/min. Thesurfaces were mounted on a 45° angle. The surfaces were abraded for 30 seconds ata time and the static, receding, and advancing contact angles along with the roll-ofangle was measured. Five of the surfaces were built up with nano particles and onewas sand blasted and anodized to create a superhydrophobic structure. The surfacesthat withstood the most abrasion was the surface that had been calcined to improveadhesion and the surface that had been sand blasted and anodized. Measurementsshowed that the roll-off angle and the receding contact angle were the two bestindicators of the deterioration of a surface, while the static contact angle and theadvancing contact angle varied little with abrasion. The project was done at thecompany Technical Research Institute of Sweden (SP) at their chemistry, surfaces andmaterials department in Stockholm. All coatings and equipment was supplied by SP.

Orientador: Mauro Pedrine Santamaria / Resumo: Estudos clínicos avaliaram diferentes opções de tratamento cirúrgico-restaurador para tratar recessões unitárias associadas à LCNC. No entanto, apesar de serem um achado comum, evidências insuficientes estão disponíveis na literatura a respeito do tratamento de recessões múltiplas associadas à LCNC e o protocolo clínico ideal para o tratamento deste tipo de lesões ainda não foi estabelecido. Dessa forma, o objetivo do presente estudo foi comparar dois protocolos multidisciplinares distintos por meio de um estudo clínico controlado e randomizado. Para tal, foram tratados 40 pacientes portadores de recessões múltiplas associadas à LCNC, os quais foram alocados aleatoriamente em um dos seguintes grupos: grupo teste (n=20), restauração parcial da lesão cervical e retalho posicionado coronariamente modificado associado ao enxerto de matriz dérmica acelular de origem suína (MCAF+PR+XDM) e grupo controle (n=20), restauração parcial da lesão cervical e retalho posicionado coronariamente modificado associado ao enxerto de tecido conjuntivo subepitelial (MCAF+PR+CTG). Após 6 meses, as taxas de recobrimento radicular foram 71,2% (2.5±1.1mm) para MCAF+PR+CTG e 59,7% (2±1.3mm) para MCAF+PR+XDM (p=0,1). MCAF+PR+CTG apresentou maior ganho de tecido queratinizado (p<0,05). MCAF+PR+XDM resultaram em menor dor pós-operatória e menor tempo de cirurgia (p=0,001). Ambos os grupos resultaram em melhorias na estética, sem diferença entre os grupos (p>0,05). Por conseguinte, dentro das limitações do... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Clinical studies assessed different surgical-restorative treatment options to lead to single recessions associated with NCCL. However, although they are a common finding, insufficient evidence is available in the literature concerning about the treatment of multiple adjacent gingival recessions associated with non-carious cervical lesions and the optimal clinical protocol for the treatment of these lesions has not been established. Thus, the aim of this study was to compare two different multidisciplinary protocols by means of a randomized controlled clinical trial. For such purpose, forty patients with multiple adjacent gingival recessions associated with NCCL were enrolled and randomly allocated to one of the following groups: test group (n=20), partial restoration of cervical lesion and modified coronally advanced flap for root coverage associated with porcine acellular dermal matrix (MCAF+PR+XDM) and control group (n=20), partial restoration of cervical lesion and modified coronally advanced flap associated with connective tissue graft (MCAF+PR+CTG). After 6 months, CD coverage rates were 71,2% (2.5±1.1mm) for MCAF+PR+CTG and 59,7% (2±1.3mm) for MCAF+PR+XDM (p=0,1). MCAF+PR+CTG resulted in greater gain of keratinized tissue (p<0,05). MCAF+PR+XDM resulted in lower postoperative pain and shorter surgical time (p=0,001). Within the limitations of the present study, both groups resulted in esthetic improvements (p>0,05). MCAF +PR + CTG and MCAF+PR+XDM were effective to treat ... (Complete abstract click electronic access below) / Mestre

O objetivo deste trabalho é estudar o impacto dos processos erosivo, abrasivo e erosivo/abrasivo sobre a camada de glaze aplicada em materiais restauradores indiretos produzidos com tecnologia CAD/CAM quanto à rugosidade superficial (Ra), à perda de superfície (PS), à topografia superficial (T) e à deposição de biofilme (DB). Este estudo teve como fatores de variação: material restaurador [LuxaCam Zircon HT - Plus (LC) e IPS e.max CAD (IPS)] e tratamento de superfície [Sinterização (S), Glaze (G), Erosão (E), Abrasão (A), Erosão/Abrasão (EA)]. Foram produzidos espécimes de 6mm x 7 mm x 1,3mm, divididos em 10 grupos para cada resposta. Para as respostas Ra e PS (n=10) foi utilizada perfilometria óptica, já para a resposta T foi utilizado MEV e para DB, ensaio microbiológico (n=3 e n=5, respectivamente). O protocolo de erosão consistiu na imersão de espécimes em 5ml de HCl 0,06M, pH 1,2, por 30 horas a 37ºC. O protocolo abrasivo foi realizado com máquina de escovação, escovas de cerdas macias e slurry pasta dentifrícia/água destilada 1:2. Foram realizados 400.000 ciclos com carga de 200 gramas. O protocolo erosivo/abrasivo consistiu na combinação dos dois protocolos anteriores. Para DB foi acrescentada a variável tempo de leitura (5 e 24 horas). Para este ensaio foi utilizada a cepa de Streptococcus mutans UA159, cultivada em TSB suplementado com 1,7% de sacarose, usando o método indireto de coloração por safranina e leitura de absorbância. Os dados foram submetidos à análise de variância (ANOVA) e teste de Tukey (p<0,05). Quanto ao Ra, LC apresentou maior Ra do que IPS (p<0,05) para todos os grupos testados. O desafio E diminuiu o Ra do glaze (p<0,05), enquanto A e EA o aumentaram (p<0,05). Quanto à PS, LC apresentou PS maior que IPS (P=0,03). Os desafios A e EA geraram maior PS do que E (p=0,00). Para DB, não houve diferença para nenhum fator após 5 horas (p>0,05). Para 24 horas, LC apresentou maior DB que IPS (P=0,00) e os desafios A e EA geraram maior DB (p=0,01) que E. A DB após 5 horas foi maior do que após 24 horas (p=0,02). Todas as propriedades da camada de glaze testadas foram alteradas pelos desafios de superfície, porém a camada de glaze aplicada sobre zircônia foi mais suscetível a estas. A maior rugosidade da camada de glaze levou à maior deposição de biofilme. / The aim of this study is to evaluate the impact of erosive, abrasive and erosive / abrasive challenges on the glaze layer applied on indirect restorative materials produced with CAD/CAM technology for surface roughness (Ra), surface loss (SL), surface topography (ST) and biofilm deposition (BD). This study had as factors of variation: restoration material [LuxaCam Zircon HT - Plus (LC) and IPS e.max CAD (IPS)] and surface treatment [Sintering (S), Glaze (G), Erosion (E), Abrasion (A), Erosion / Abrasion (EA)]. Specimens of 6mm x 7mm x 1.3mm were produced and divided into 10 groups for each response. For Ra and SL responses (n = 10) was used optical profilometry, for ST was used SEM (n=3) and for BD was used microbiological assay (n = 5). The erosion protocol consisted of immersing specimens in 5ml of 0.06M HCl, pH 1.2, for 30 hours at 37ºC. The abrasive protocol was performed with brushing machine, soft bristle brushes and slurry toothpaste /distilled water 1: 2. 400.000 cycles were performed with a load of 200 grams. The erosive / abrasive protocol consisted of a combination of the two previous protocols. For BD the variable reading time was added (after 5 and 24 hours). Strains of Streptococcus mutans UA159, cultivated in TSB supplemented with 1.7% of sucrose, were used by the indirect method of staining with safranin and reading of absorbance. Data were submitted to analysis of variance (ANOVA) and Tukey test (p <0.05). Regarding Ra, LC presented higher Ra than IPS (p <0.05) for all groups tested. E decreased glaze Ra (p <0.05), while A and AE increased it (p <0.05). Regarding SL, LC presented SL higher than IPS (P = 0.03). A and EA challenges generated higher SL than E (p = 0.00). For BD, there was no difference for any factor after 5 hours (p> 0.05). For 24 hours, LC presented higher BD than IPS (P = 0.00) and A and EA challenges generated higher BD (p = 0.01) than E. BD after 5 hours was higher than after 24 hours (p = 0.02). All the glaze layer properties tested were altered by the surface challenges, however the glaze layer applied on zirconia was more susceptible to these. Greater roughness of the glaze layer led to greater biofilm deposition.