Influ��ncia da pot��ncia de laser Nd: YAG na soldagem do a��o inoxid��vel duplex UNS S32205

P��s-gradua����o em Engenharia Mec��nica - FEIS

A����o do fluor na microdureza do esmalte humano submetido a dois tipos de agentes clareadores

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

An��lise da superf��cie de cer��micas de dissilicato de l��tio ap��s imers��o em solu����es ��cidas e a base de fl��or

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Estudo da dureza e da resist��ncia �� compress��o de resinas compostas para dentes posteriores ap��s a imers��o em ��gua destilada. Efeito da aplica����o de selante superficial

Novos comp��sitos t��m surgido no mercado especificamente destinados �� confec����o de restaura����es est��ticas posteriores. Entretanto, embora tais materiais apresentem resultados iniciais animadores, h�� a necessidade de comprova����es adicionais para que possam ser utilizados com seguran��a. Resinas compostas posteriores s��o submetidas a estresses complexos de compress��o e abras��o durante a mastiga����o e a aplica����o de selantes superficiais tem sido relatada como forma de aumentar a resist��ncia ao desgaste destes materiais. O presente trabalho teve como prop��sito avaliar a dureza e a resist��ncia �� compress��o das resinas compostas Alert (Jeneric/Pentron), Ariston (Vivadent), Definite (Degussa), P60 (3M), Solitarie (Kulzer), Surefil (Dentsply) e Z100 (3M) ap��s 90 dias de imers��o em ��gua destilada, recobertas com selante Protect It (Jeneric/Pentron) e submetidas �� ciclagem mec��nica (10.000 ciclos, 600N, 5Hz). Os ensaios de dureza (n=8) foram realizados em aparelho Wolpert, com diamante Vickers e peso de 50gf aplicado por 30 segundos, antes e ap��s per��odos de imers��o de 30, 60 e 90 dias. Os ensaios de resist��ncia �� compress��o (n=8) foram realizados somente ap��s 90 dias, em corpos-de-prova cil��ndricos medindo 8mm de altura por 4mm de di��metro. Apenas os esp��cimes destinados �� compress��o foram ciclados mecanicamente. Os ensaios foram realizados em m��quina MTS 810, equipada com c��lula de carga de 10kN (ciclagem) e 100kN (compress��o) e velocidade de 0,5mm/min. Ap��s an��lise de vari��ncia (p<0,05), os resultados mostraram, previamente �� imers��o, maiores valores de dureza para os materiais Z100 (74,253VHN) e Ariston (71,308VHN). A seguir, com valor semelhante �� resina Ariston, mas inferior �� resina Z100, apresentou-se o material Surefil (69,969VHN)...(Resumo completo, clicar acesso eletr��nico abaixo)

An��lise de corros��o, dureza e fratura de conjuntos implantes / componentes prot��tico de Tit��nio c.p., ap��s serem submetidos a ciclos de fadiga em um meio fluoretado com diferentes PH

Atualmente o tit��nio �� empregado como biomaterial devido �� sua biocompatibilidade e resist��ncia �� corros��o. Entretanto, ��ons fluoretos, freq��entemente empregados em dentifr��cios bucais, podem interferir no processo de corros��o. O objetivo deste estudo foi analisar a influ��ncia de um meio fluoretado com diferentes pH nas propriedades mec��nicas e na resist��ncia �� corros��o dos conjuntos implantes/componentes prot��ticos �� base de Ti c.p., a partir dos testes de fadiga, microscopia eletr��nica de varredura (MEV) e dureza. Foram simulados cinco anos de uso regular de meios de higiene oral com conte��do de 1500 ppm de NaF, com dois diferentes pH, 7,4 e 5,3, mediante imers��o das amostras nesses meios durante 184 horas e tamb��m em ��gua destilada, grupo controle. As amostras foram testadas num dur��metro Micromet 2001 (500gf/30s). Os dados dos testes de dureza foram analisados pelo teste de Wilcoxon, demonstrando que as amostras sofreram influ��ncia negativa na dureza ap��s a a����o dos ��ons fluoreto. Entretanto, essa influ��ncia n��o ocorreu nos testes de fadiga realizados em uma m��quina de ensaios mec��nicos MTS-810, fixada a 100.000 ciclos, 15Hz e programada com for��a de fadiga a 150 N. Pela an��lise de MEV foram constatadas evid��ncias de corros��o na superf��cie das amostras ap��s a����o de ��ons fluoretos, entretanto pelo EDS n��o se verificou incorpora����o de ��ons fluoretos sobre a superf��cie dos conjuntos. Concluiu-se que a concentra����o de fl��or e o pH das solu����es n��o exerceram influ��ncia nas propriedades mec��nicas.

Estudo do comportamento em fadiga de uma chapa de a��o microligado, grau API 5L X70

In engineering, for correct designing the structural components required for cyclical stresses, it is necessary to determine a limit of resistance to fatigue, which is the maximum amplitude of the applied tension under which the fatigue failure does not occurs after a certain number cycles. The marine environment is hostile, not only by the high pressure, corrosion, but also by low temperatures. Petrol Production units, composed of the risers (pipelines connecting the oil well to the ship), are dimensioned to remain installed for periods of 20 up to 30 years, and must therefore be prepared to support various efforts, such as tidal, wind currents and everything that is related. This paper focuses on a study on the fatigue behavior of microalloyed steel, API 5L Grade X70, used to transport oil and gas by pipelines. For analysis, we obtained the curves S-N (stress vs. number of cycles) using laboratory data collected from cylindrical longitudinal and transverse specimens used in axial fatigue test in accordance with ASTM E466. The tensile tests and microhardness were performed to characterize the mechanical properties of the samples, and it was found that the values meet the specifications of the standard API 5L. To characterize microstructurally the material, it was also made a metallographic analysis of the steel under study, and the origin of the fatigue crack was investigated with the support of a scanning electron microscope (SEM).

Avalia����o do comportamento mec��nico sob deforma����o da liga Ti- 30Ta visando aplica����es biom��dicas

Titanium and its alloys have been used for biomedical applications due their excellent properties such as high corrosion resistance, biocompatibility and mechanical properites. In this study, microstructural and mechanical properties of Ti-30Ta alloy was evaluated during its processing. Ti-30Ta alloy ingots were produced from sheets of commercially pure titanium (99.9%) and tantalum (99.9%). Its melting was realized in arc melting furnace in an argon atmosphere. After homogenizing at 1200��C, ingots were cold worked by swaging. Samples with 13 mm in diameter were obtained. They were forging at the reduction ratios of 15%. After deformation, microstructure was evaluated by optical microscopy in each condition. Also, Vickers microhardness of samples was measured and phase constitution was evaluated using XRD analysis

Propriedades f��sicas de vidros Sb2O3-P2O5

This work presents experimental results of some physical properties of antimony phosphate glasses with compositions (x) Sb2O3 - (1-x) P2O5 (x = 0.75, 0.85, 0.90). Mechanical, thermal, optical and electrical properties were investigated: density, elastic moduli (Young's moduli and Poisson's ratio), Vickers microhardness, coefficient of thermal expansion, glass transition temperature, refractive index and electrical conductivity (for x = 0.75). There was no evidence of electronic conductivity by bipolaron hopping. Measurements of energy dispersive spectroscopy (EDS) showed that volatilization of Sb2O3 takes place during the glass melting

Estudo em fadiga no a��o API 5L X80 soldado pelo processo HF/ERW

The technological advancement in order to improve the methods of obtaining energy sources such as oil and natural gas is mainly motivated by the recent discovery of oil reserves. So, increasingly , there is a need for a thorough knowledge of the materials used in the manufacture of pipelines for transportation and exploration of oil and natural gas. The steels which follow the API standard (American Petroleum Institute), also known as high strenght low alloy (hsla), are used in the manufacture of these pipes, as they have, with their welded joints, mechanical properties to withstand the working conditions to which these ducts will be submitted . The objective of this study is to evaluate the fatigue behavior in microalloyed steel grade API 5L X80 welded by process HF / ERW . For this, axial fatigue tests to obtain S-N curve (stress vs. number of cycles ) were conducted. To complement the study, it was performed metallographic , fractographic , Vickers hardness tests and tensile tests to characterize the mechanical properties of the steel and check whether the values satisfy the specifications of the API 5L standard . From the fatigue tests , it was concluded that the surface finish influences directly on the fatigue life of the material

Estudo de cer��micas avan��adas para fins de blindagem bal��stica

The research involving new materials has always been considered as a differential in the development of a technology company. This occurred naturally since ancient times, often motivated by reasons of a certain age, where the most common material used was also the name of your time and may be cited as an example the Bronze Age, and later was the Iron. Currently, the use of firearms are they used in resolving conflicts between countries, or a more equivocal, as an instrument of social banditry make innovations in the area of shielding welcome, whether for personal use, in the form of vests or vehicle such as cars, tanks and even aircraft. In this context, is a Silicon Carbide Ceramic, with low density and high hardness. Thus, the aim of this study is the evaluation and comparison of these materials, seeking to improve their properties by means of additives such as boron and silicon metal and amorphous YAG. For this work, the specimens were pre-shaped by means of uniaxial later to be referred for isostatic pressing and sintering. The maximum percentage for each additive was 5%, except for the YAG whose percentage was 8.2% (mass percentage). All compositions were subjected to the same tests (x-ray diffraction, apparent density, optical microscopy, Vickers hardness, scanning electron Microscopita), so that one could draw a comparison between the materials under study, samples that showed better mechanical properties and micro structural, related here by hardness testing and microscopy (optical and SEM) were the silicon carbide doped with YAG and alumina samples, demonstrating the potential of these materials for ballistic protection. Other compositions have high porosity, which is highly undesirable, since in order to harmful influences on the mechanical properties discussed below

Caracteriza����o de cer��micas a base de nitreto de sil��cio para aplica����es estruturais

The need for development of new materials is a natural process in the companies��� technological point of view, seeking improvements in materials and processes. Specifically, among the materials, ceramic exhibit valuable properties, especially the covalent ceramics which have excellent properties for applications which requires the abrasion resistance, hardness, high temperatures, resistence, etc. being a material that has applications in several areas. Most studies are related to improvement of properties, specially fracture toughness that allows the expansion of its application. Among the most promising ceramic materials are silicon nitride (Si3N4) which has excellent properties. The goal of this work was the development and caracterization of Si3N4-based ceramics, doped with yttrium oxide (Y2O3), rar earth concentrate (CTR2O3) and cerium oxide (CeO2) in the same proportion for the evaluation of properties. The powders' mixtures were homogenized, dried and compressed under pressure uniaxial and isostatic. Sintering was carried out in 1850 ���C under pressure of 0,1MPa N2 for 1 h with a heating rate of 25 ���C / min and cooling in the furnace inertia. The characterizations were performed using Archimedes principle to relative density, weight loss by measuring before and after sintering, phase analysis by X-ray diffraction, microstructure by scanning electron microscope (SEM), hardness and fracture toughness by the method Vickers indentation. The results obtained showed relative density of 97-98%, Vickers hardness 17 to 19 GPa, fracture toughness 5.6 to 6.8 MPa.m1/2, with phases varying from ��-SiAlON and ��-Si3N4 depending the types of additives used. The results are promising for tribological applications and can be defined according to the types of additives to be used

Dureza e rugosidade superficial de cimentos de ion��mero de vidro ap��s ensaio de escova����o

To evaluate the surface roughness and Vickers hardness of glass ionomer cements Ketac Molar�� and Ketac Molar Easy Mix�� (ESPE Dental AG) after brushing. Methods ��� After roughness and hardness tests of 14 specimens of each material, they were submitted to 30,000 brushing cycles and new analysis of roughness and hardness. Statistical analysis showed that there was no significant difference between the materials in relation to the initial roughness. Results ��� However, after brushing there was higher surface roughness for Ketac Molar Easy Mix��. For both materials, there was increase of hardness after brushing and the highest values were presented by Ketac Molar Easy Mix��. Conclusion ��� It can be concluded that, when choosing a glass ionomer cement for restoration it should be preferred to Ketac Molar, because it showed hardness similar to Ketac Molar Easy Mix, but it was less rough.

Influence of heat treatment and mechanical cycling on hardness and fracture analysis of Ti35Nb5Zr casting alloy

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Efeito de fontes de luz na microdureza de resinas compostas

This study assessed the surface microhardness of compound resins cured by different light sources. Methods Three micro hybrid (Vit-l-escence, Amelogen Plus, Opallis) and one nanoparticle (Filtek Z350, 3M ESPETM Dental Products, St. Paul, USA) compound resins were selected. The resins were polymerized by a halogen light unit (Ultralux, Dabi Atlante, Ribeir��o Preto, Brasil) with two tips, one semi-guided made of glass and another of painted acrylic and a LED-based source (UltraLume 2, Ultradent��, South Jordan, USA). Specimens constructed from a circular aluminum matrix were photopolymerized for 40 second after they received the compound resin and stored dry for 24 hours. After this period, a Vickers surface microhardness assay was performed, measuring the top (hardness 1) and base (hardness 2) surfaces four times each. Variance analyses were complemented by Newman-Keuls method, with significance set at 5%. Results The Opallis (FGM, Santa Catarina, Brasil) resin subjected to UltraLume 2 (Ultradent��, South Jordan, USA) obtained the lowest mean hardness values for the top surface. The Vit-l-escence (Ultradent��, South Jordan, USA) compound cured by Led UltraLume 2 (Ultradent��, South Jordan, USA) and by Ultralux PCP (Dabi Atlante, Ribeir��o Preto, Brasil) halogen light obtained the highest mean hardness, followed by the Filtek Z350 (3M ESPETM Dental Products, St. Paul, USA) resin subjected to UltraLume 2 (Ultradent�� South Jordan, USA). The Opallis (FGM, Santa Catarina, Brasil) resin cured by LED UltraLume 2 (Ultradent��, South Jordan, USA) also obtained the lowest mean hardness for the base surface and the Vit-L-Escence (Ultradent��, South Jordan, USA) resin obtained the highest value, followed by Amelogen Plus, when cured by Ultralux (Dabi Atlante, Ribeir��o Preto, Brasil) using the semi-guided tip. Conclusion The polymerization and, consequently, the microhardness achieved by the LED unit was equivalent to those achieved by conventional halogen units for three of the four composites tested.

Effect of different light-curing techniques on hardness of a microhybrid dental composite resin

Coordena����o de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)