O aço SAE AISI 52100 com microestrutura martensítica revenida é utilizado para a fabricação de rolamentos como também na fabricação de outras peças e dispositivos para aplicações marinhas. A modificação deste aço com a adição de silício e manganês pode melhorar as propriedades mecânicas em média-alta temperatura. Este aço modificado ao Si e Mn apresenta grande resistência ao amolecimento durante o revenimento, o que pode ser explorado quanto ao comportamento em altas temperaturas. Para a realização deste trabalho, foi utilizado o aço AISI 52100 com composição química conforme estabelece a norma ASTM A295- 2014, e um aço experimental com 1,82% de Si e 1% de Mn baseado no aço AISI 52100. Após tratamento térmico de normalização, investigou-se os fenômenos de transformação de fase por meio de estudos microestruturais, mecânicos e corrosivos em diferentes temperaturas. A adição de Si e Mn junto ao tratamento de normalização conferiram melhor dureza, tenacidade ao impacto e maior resistência à tração a 25, 300 e 400 oC, porém diminuiu a resistência à corrosão comparada à do aço AISI 52100 na condição utilizada nas indústrias. Portanto, o aço modificado normalizado se mostrou adequado para utilização em maiores temperaturas que não exijam resistência à corrosão em solução de NaCl 3,5 %p. / SAE AISI 52100 steel with tempered martensitic microstructure is used for the manufacture of bearings as well as in the manufacture of other parts and devices for marine applications. The modification of this steel with the addition of silicon and manganese can improve the mechanical properties in medium-high temperature. This Si-Mn modified steel exhibits high resistance to softening during tempering, which can be exploited in high temperature behavior. For this work, it was used the AISI 52100 steel with chemical composition in accordance to ASTM A295- 2014 and an experimental steel with 1.82% Si and 1% Mn, based on AISI steel 52100. After normalization heat treatment, the phenomena of phase transformation were investigated through microstructural, mechanical and corrosive studies at different temperatures. The addition of Si and Mn together with the normalization treatment improve hardness, impact toughness and tensile strength at 25, 300 and 400 oC, but decreased the corrosion resistance compared to AISI 52100 steel in the condition used in the industries. Therefore, normalized modified steel proved to be suitable for use at higher temperatures that do not require corrosion resistance in 3.5%w. NaCl solution.

Made available in DSpace on 2014-12-17T14:57:54Z (GMT). No. of bitstreams: 1 JanainaSS.pdf: 6774864 bytes, checksum: 445b5e932b89fcc09c4b97403b959e26 (MD5) Previous issue date: 2009-10-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Low cost seals are made of NBR, Nitrile Butadiene Rubber, a family of unsaturated copolymers that is higher resistant to oils the more content of nitrile have in its composition, although lower its flexibility. In Petroleum Engineering, NBR seal wear can cause fluid leakage and environmental damages, promoting an increasing demand for academic knowledge about polymeric materials candidate to seals submitted to sliding contacts to metal surfaces. This investigation aimed to evaluate tribological responses of a commercial NBR, hardness 73 ? 5 Sh A, polytetrafluoroethylene (PTFE), hardness 60 ? 4 HRE and PTFE with graphite, 68 ? 6 HRE. The testings were performed on a sliding tribometer conceived to explore the tribological performance of stationary polymer plane coupons submitted to rotational cylinder contact surface of steel AISI 52100, 20 ? 1 HRC Hardness, under dry and lubricated (oil SAE 15W40) conditions. After screening testings, the normal load, relative velocity and sliding distance were 3.15 N, 0.8 m/s and 3.2 km, respectively. The temperatures were collected over distances of 3.0?0.5 mm and 750?50 mm far from the contact to evaluate the heating in this referential zone due to contact sliding friction by two thermocouples K type. The polymers were characterized through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The wear mechanisms of the polymer surfaces were analyzed by Scanning Electron Microscopy (SEM) and EDS (Energy-Dispersive X-ray Spectroscopy). NBR referred to the higher values of heating, suggesting higher sliding friction. PTFE and PTFE with graphite showed lower heating, attributed to the delamination mechanism / Retentores de baixo custo s?o comercialmente dispon?veis de NBR, copol?meros insaturados de borrachas de nitrilo-butadieno que s?o mais resistentes aos ?leos quanto mais altos forem seus teores de nitrila, ? custa de uma menor flexibilidade. Em Engenharia de Petr?leo, o desgaste dos retentores de NBR causa vazamento de fluidos e danos ambientais, provocando uma crescente demanda de conhecimento acad?mico sobre materiais polim?ricos candidatos a retentor submetidos a contatos de deslizamento com superf?cies de metal. Este trabalho objetivou avaliar respostas tribol?gicas de tr?s pol?meros comercialmente dispon?veis, NBR, dureza 73 ? 5 Sh A, polytetrafluoroethylene (PTFE), dureza 60 ? 4 HRE e PTFE com grafite, 68 ? 6 HRE. Os ensaios foram realizados em um trib?metro de deslizamento concebido para explorar o desempenho tribol?gico de corpos-de-prova polim?ricos estacion?rios de superf?cie plana submetidos a um contato seco ou lubrificado (?leo SAE 15W40) de uma superf?cie rotativa cil?ndrica de a?o 52100, dureza 20 ? 1 HRC. A carga normal, a velocidade relativa e a dist?ncia de deslizamento foram, respectivamente, 3,15 N, 0,8 m/s e 3,2 km, determinadas ap?s ensaios explorat?rios iniciais. As temperaturas foram medidas por dois termopares tipo K a 3,0?0,5 mm e 750?50 mm de dist?ncia do contato para avaliar-se o aquecimento em uma mesma regi?o devido ao atrito de deslizamento no contato. Os pol?meros foram caracterizados atrav?s de An?lises Termogravim?tricas (TGA), Calorimetria Diferencial Explorat?ria (DSC) e An?lises Din?mico-Mec?nica (DMA). Os mecanismos de desgaste das superf?cies dos pol?meros foram analisados por Microscopia Eletr?nica de Varredura (MEV) e EDS (Espectroscopia por Energia Dispersiva de Raios-X). NBR apresentou os maiores valores de aquecimento, sugerindo maior atrito de deslizamento. PTFE e PTFE grafitado apresentaram um menor aquecimento, atribu?do ao mecanismo de desgaste por delamina??o

The potential for significant performance increases, using ceramic materials in un-lubricated rolling element bearing applications, has been the subject of research over the past two decades. Practical advantages over steel include increased ability to withstand high loads, severe environments and high speeds. However, widespread acceptance has been limited by the inability to predict wear life for ceramic bearing applications. In this thesis, the rolling contact wear of 52100 bearing steel and Over-aged Magnesia-Partially-Stabilised Zirconia (OA-Mg-PSZ) ceramic are examined using a newly developed rolling contact wear test rig. The new wear test rig simulates the system geometry of an un-lubricated hybrid (ceramic and steel) ball bearing. The new wear test rig is versatile in that it allows low cost samples to be utilised resulting in a larger number of samples that can be tested. Wear samples of 52100 bearing steel and OA-Mg-PSZ produced by the new wear test rig were examined for mass loss and wear depth. The wear behavior of both the steel and ceramic material showed a dependence on operating variables time and load. Load was varied between 300N to 790N. Typical mass loss after 1 hour of testing 52100 bearing steel at 790N was 0.03 grams as compared to OA-Mg-PSZ which was 0.001 grams. The rolling contact wear of the OA-Mg-PSZ was an order of magnitude lower than that of the 52100 bearing steel. The wear mechanism for 52100 bearing steel was typical of plastic deformation and shearing near and below the surface of rolling contact. Once cracks extend to reach the surface, thin flat like sheets are produced. In OA-Mg-PSZ the wear mechanism initially is that of plastic deformation on the scale of the surface asperities with asperity polishing occurring followed by lateral cracks and fatigue spallation. Results obtained using the new rolling contact wear test rig led to the establishment of a new equation for wear modeling of 52100 bearing steel and OA-Mg-PSZ ceramic materials.

Der Wissenschaftsrat berät Bund und Länder bei der inhaltlichen und strukturellen Entwicklung von Hochschulen, von Wissenschaft und Forschung. So hat er in den letzten Jahren maßgeblich den Exzellenzwettbewerb zwischen den Hochschulen mitgeprägt. Auch mit den Infrastruktureinrichtungen, etwa mit den Rechenzentren oder mit den wissenschaftlichen Bibliotheken, befassen sich die Gremien die Wissenschaftsrats angesichts der Herausforderungen weltweiter digitaler Vernetzung.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-05-30T23:20:43Z No. of bitstreams: 1 AlineCristinaMendesDeFarias_TESE.pdf: 9556716 bytes, checksum: 2350df4b9bbb084a66c9da511159a31d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-01T23:15:21Z (GMT) No. of bitstreams: 1 AlineCristinaMendesDeFarias_TESE.pdf: 9556716 bytes, checksum: 2350df4b9bbb084a66c9da511159a31d (MD5) / Made available in DSpace on 2016-06-01T23:15:21Z (GMT). No. of bitstreams: 1 AlineCristinaMendesDeFarias_TESE.pdf: 9556716 bytes, checksum: 2350df4b9bbb084a66c9da511159a31d (MD5) Previous issue date: 2015-07-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A lubricidade do biodiesel interfere no funcionamento normal dos sistemas de inje??o diesel, principalmente dos bicos injetores, reduzindo o desgaste e elevando o tempo de vida da linha de alimenta??o do motor. O m?todo HFRR (High Frequency Reciprocating Rig) ? um ensaio padr?o para avalia??o da lubricidade do diesel/biodiesel (ASTM D6079), consistindo principalmente da medi??o da escara de desgaste impressa na esfera numa sonda de movimento alternado sob alta frequ?ncia. Quando o desgaste se desenvolve, algumas caracter?sticas din?micas do sistema variam, resultando em desvios significativos nos padr?es dos sinais de vibra??o, ac?sticos e de atrito. A aquisi??o e caracteriza??o das assinaturas desses sinais obtidos durante os ensaios tribol?gicos representam uma importante ferramenta n?o intrusiva de avalia??o da lubricidade desses combust?veis, cuja representa??o no dom?nio do tempo nem sempre revelam informa??es triviais, sendo necess?ria sua transforma??o para o dom?nio da frequ?ncia usando a Transformada r?pida de Fourier (FFT) do sinal. A presente tese objetivou desenvolver uma forma din?mica de avalia??o de lubricidade de combust?veis (Diesel S50, ?ster Met?lico de Soja e blendas B10 e B20) em bancada HFRR (contato esfera-disco plano), e melhoria aos referenciais metodol?gicos da ASTM D6079, aplicando t?cnicas de an?lise de sinais (vibra??o e n?vel de press?o sonora) e sua associa??o com par?metros disponibilizados pela norma ASTM D6079 (di?metro da escara de desgaste) com dura??o de 75, 120 e 180 minutos. Os perfis e par?metros de rugosidade e an?lise microsc?pica dos discos foram usados para melhor avaliar a influ?ncia do tempo e do combust?vel na evolu??o do desgaste do disco. Nesta avalia??o, a lubricidade dos combust?veis aumentou com o teor de biodiesel utilizado e diminuiu com o aumento do n?mero de ciclos aplicado. A an?lise temporal e o espectro de frequ?ncia dos sinais demonstraram sensibilidade com a mudan?a do combust?vel, o n?mero de ciclos e, consequentemente, com a evolu??o do desgaste pelo uso prolongado dos combust?veis, estando, assim, correlacionados entre si e com os resultados dispon?veis pela ASTM. / The lubricity of biodiesel interferes in the normal operation of diesel injection systems, especially in nozzles. It can reduce the wear and raise the lifetime of the engine supply line. The method HFRR (High Frequency Reciprocating Rig) is a standard test for evaluation of diesel/ biodiesel lubricity (ASTM D6079). The HFRR lubricity evaluation mainly consists of measuring the printed scar wear on the ball. When wear is developing, some dynamic features of the system vary and it results in significant changes in the patterns of vibration, sound pressure level (SPL) and friction signals. The acquisition and characterization of signatures of these signals obtained during tribological tests are an important non-intrusive tool for evaluating of the lubricity of these fuels, whose representation in the time domain not always reveals trivial information. This requires signal transformation to the frequency domain using the Fast Fourier Transform (FFT) and Short-Time Fourier Transform (STFT) analyses. This thesis aimed to develop a dynamic assessment of lubricity fuels (Diesel S50, Methyl Ester of Soybean and B10 and B20 blends) in HFRR bench (ball-on-flat disk contact), and improving the methodological framework of ASTM D6079 standard by application of signal analysis techniques (vibration and SPL) and its association with parameters provided by ASTM D6079 (wear scar diameter) lasting 75, 120 and 180 minutes. The profiles and topographic parameters of scars and their microscopic analysis were used to further evaluate the influence of the time and fuel in the wear evolution of disk. In this evaluation, the fuel lubricity was influenced by increasing of biodiesel content and decreasing of number of cycles applied. From the temporal and frequency spectrum analysis of the vibration and NPS signals it is shown that both vibration and NPS stablish a relation with fuel lubricity, biodiesel content, number of cycles and parameters of profiles from scar of discs.

<p> Case hardening of steels is extensively used throughout general engineering to produce components with a hardened layer whilst retaining a tough core. This is usually accomplished using different sources of energy, e.g. flame and induction being the most common. In recent years, a new case hardening technology, named 'Grind-Hardening' has surfaced. In this method, the heat dissipated during grinding is utilized to induce martensitic phase transformation in the surface layer of a component. Therefore it is possible to incorporate grinding and surface hardening into a single operation to develop a cost-effective production method. The grinding process then becomes an integrated heat treatment process.</p> <p> In the present study on 'grind hardening', a numerical thermal model has been developed to compute the temperature distribution beneath the ground surface to predict the extent of surface hardening and the case depth. Grinding experiments were conducted in order to examine the influence of various process variables such as wheel depth of cut, feed speed, and wheel preparation. AISI 52100 and 1045 steels were used in this study to evaluate the behavior of plain and alloy steels during grind hardening. Effective case depth was measured using a Vickers hardness tester and was found to be over 0.5 mm for a target hardness of 513 Hv. Microstructure was analyzed using optical and scanning electron microscopes. The microstructure was observed to have fine martensitic laths which give rise to remarkable high hardness.</p> / Thesis / Master of Applied Science (MASc)

No description available.

High rolling contact fatigue parts are vital for the long service life of fuel pumps. Cummins Fuel Systems are currently using an M2 tool steel for one of the most important roller bearing application in their pumps, namely the cam follower. The future design of the cam follower is a pin-less tappet roller. The wear and fatigue properties of the roller is vital to ensure reliability of the fuel system. M2 tool steel is an expensive material and becomes even more so if diamond like coating (DLC) is needed to decrease the friction coefficients. To cut costs of the fuel pump it might be possible to replace the M2 tool steel with 52100 steel (100Cr6). Competitive methods have proven that carbonitrided 52100 can reach excellent wear and fatigue properties making it a candidate to replace M2 tool steel. How the properties of hardness, toughness and compressive residual stresses are developed in 52100 and how they affect the fatigue and wear resistance has been researched from the literature. A big part of this project was to do an extensive analysis of a roller bearing that was believed to have gone through one of these competitive methods that produce excellent wear and fatigue resistance. The analysis was done with background to the knowledge gathered from the literature. Finally process trials were set up to carbonitride 52100 steel samples. The trials were done to develop a better understanding of how adding carbon together with nitrogen to the surface of 52100 steel will influence the metallurgical parameters that results in good wear and fatigue resistance. From this analysis Cummins hope to create a process recipe that can be used for carbonitriding the cam follower and maybe other components in their fuel systems.

No description available.