Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-22T17:05:55Z No. of bitstreams: 1 LeonardoChagasDaSilva_DISSERT.pdf: 18388344 bytes, checksum: fd0fcc6b7f339008972288ae66a8bd8e (MD5) / Approved for entry into archive by Monica Paiva (monicalpaiva@hotmail.com) on 2017-03-22T17:09:55Z (GMT) No. of bitstreams: 1 LeonardoChagasDaSilva_DISSERT.pdf: 18388344 bytes, checksum: fd0fcc6b7f339008972288ae66a8bd8e (MD5) / Made available in DSpace on 2017-03-22T17:09:55Z (GMT). No. of bitstreams: 1 LeonardoChagasDaSilva_DISSERT.pdf: 18388344 bytes, checksum: fd0fcc6b7f339008972288ae66a8bd8e (MD5) Previous issue date: 2015-08-06 / No sistema de alimenta??o de combust?vel dos motores do ciclo diesel, o bico injetor ? uma pe?a chave para determinar o desempenho e o n?vel de emiss?es que esses motores geram. Foram feitas mudan?as significativas na composi??o dos combust?veis, nas legisla??es que regulamentam as emiss?es de poluentes e, em uma escala bem menor, houve alguns estudos detalhados do impacto dessas mudan?as nos componentes dos motores, como por exemplo, o bico injetor. O biodiesel ? um combust?vel alternativo que vem de origem vegetal, ? renov?vel, biodegrad?vel e ambientalmente correto, produzido por uma rea??o de transesterifica??o de gordura animal ou vegetal. Atualmente, o B6 vem sendo substitu?do pelo B7 por quest?es de regulamenta??es na matriz energ?tica do Brasil. O presente estudo teve como objetivo avaliar os principais mecanismos de falhas que atuam nos componentes de um bico injetor, em particular, na agulha do injetor, situada na ponta do bico. Este trabalho foi dividido em tr?s etapas: na primeira delas, foi feito um estudo de campo, com visitas ?s oficinas mec?nicas especializadas na manuten??o do sistema de inje??o diesel, para elabora??o de um relat?rio sobre as problem?ticas encontradas neste sistema. Na segunda, realizaram-se ensaios em uma bancada contendo um grupo motor-gerador, onde foram avaliados dois biocombust?veis: B6 e B6 aditivado, a fim de levantar par?metros de desempenho dos biodieseis, que permitissem avaliar o desgaste qualitativo da superf?cie dessas agulhas. Por fim, a ?ltima etapa consistiu da an?lise microsc?pica da superf?cie desgastada das agulhas do bico injetor, estas foram analisadas por microscopia eletr?nica de varredura (MEV), Energy Dispersive X-Ray Diffraction (EDS) e por espectroscopia Raman. Os resultados mostram que o motor que utilizou o B6 apresentou melhor desempenho em consumo espec?fico e temperatura de funcionamento do bico injetor mais baixa em compara??o com o motor que utilizou B6 aditivado. Al?m disso, tamb?m foi poss?vel observar a presen?a do fen?meno do scuffing no guia da agulha do primeiro motor e, pits de oxida??o na mesma regi?o da agulha do bico injetor que utilizou B6 aditivado. Por fim, a ?ltima etapa consistiu da an?lise microsc?pica da superf?cie desgastada das agulhas do bico injetor, estas foram analisadas por microscopia eletr?nica de varredura (MEV) e por espectroscopia Raman. Os resultados mostram que o motor que utilizou o B6 apresentou melhor desempenho em consumo espec?fico e temperatura de funcionamento do bico injetor mais baixa em compara??o com o motor que utilizou B6 aditivado. / No sistema de alimenta??o de combust?vel dos motores do ciclo diesel, o bico injetor ? uma pe?a chave para determinar o desempenho e o n?vel de emiss?es que esses motores geram. Foram feitas mudan?as significativas na composi??o dos combust?veis, nas legisla??es que regulamentam as emiss?es de poluentes e, em uma escala bem menor, houve alguns estudos detalhados do impacto dessas mudan?as nos componentes dos motores, como por exemplo, o bico injetor. O biodiesel ? um combust?vel alternativo que vem de origem vegetal, ? renov?vel, biodegrad?vel e ambientalmente correto, produzido por uma rea??o de transesterifica??o de gordura animal ou vegetal. Atualmente, o B6 vem sendo substitu?do pelo B7 por quest?es de regulamenta??es na matriz energ?tica do Brasil. O presente estudo teve como objetivo avaliar os principais mecanismos de falhas que atuam nos componentes de um bico injetor, em particular, na agulha do injetor, situada na ponta do bico. Este trabalho foi dividido em tr?s etapas: na primeira delas, foi feito um estudo de campo, com visitas ?s oficinas mec?nicas especializadas na manuten??o do sistema de inje??o diesel, para elabora??o de um relat?rio sobre as problem?ticas encontradas neste sistema. Na segunda, realizaram-se ensaios em uma bancada contendo um grupo motor-gerador, onde foram avaliados dois biocombust?veis: B6 e B6 aditivado, a fim de levantar par?metros de desempenho dos biodieseis, que permitissem avaliar o desgaste qualitativo da superf?cie dessas agulhas. Por fim, a ?ltima etapa consistiu da an?lise microsc?pica da superf?cie desgastada das agulhas do bico injetor, estas foram analisadas por microscopia eletr?nica de varredura (MEV), Energy Dispersive X-Ray Diffraction (EDS) e por espectroscopia Raman. Os resultados mostram que o motor que utilizou o B6 apresentou melhor desempenho em consumo espec?fico e temperatura de funcionamento do bico injetor mais baixa em compara??o com o motor que utilizou B6 aditivado. Al?m disso, tamb?m foi poss?vel observar a presen?a do fen?meno do scuffing no guia da agulha do primeiro motor e, pits de oxida??o na mesma regi?o da agulha do bico injetor que utilizou B6 aditivado. Por fim, a ?ltima etapa consistiu da an?lise microsc?pica da superf?cie desgastada das agulhas do bico injetor, estas foram analisadas por microscopia eletr?nica de varredura (MEV) e por espectroscopia Raman. Os resultados mostram que o motor que utilizou o B6 apresentou melhor desempenho em consumo espec?fico e temperatura de funcionamento do bico injetor mais baixa em compara??o com o motor que utilizou B6 aditivado.

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To improve the lifetime, enhance engine performance, decrease emissions, and inhibit tribological failures of fuel injection system components, the component materials need to resist scuffing under conditions of high temperatures, high pressures, and low viscosity fuel lubrication. The objectives of this dissertation are to improve the materials implemented in future fuel injection system designs by developing a laboratory-scale experimental method to induce scuffing on baseline steel materials and use this experimental method to evaluate various materials for their resistance to scuffing failures. An experimental method to reliably produce scuffing events on AISI 52100 steel was developed by altering the contact condition parameters of previous experimental methods, such as the counterbody material, sliding velocities, and normal loads, amongst other parameters. The proposed method allows for the rapid evaluation of surfaces and coatings for their suitability in fuel injection system applications. Multiple materials were evaluated for their friction and wear reduction properties, including three different compositions of additively manufactured steels, tungsten carbide and cobalt-based thermal spray coatings, chromium nitride coatings, diamond-like carbon coatings, and tribocatalytic MoVN-Cu coatings. The results indicate that several of the coating materials and one of the additively manufactured steel alloys are promising candidates for implementation in emerging fuel injection systems to lower friction and prevent scuffing and wear. The properties of these materials responsible for their superior tribological behavior, such as the mechanical and thermal properties, were characterized and discussed.

Mobile Miner 40V is a machine used for rock excavation and developed by Epiroc. This machine is equipped with a large cutter wheel to perform the excavation. After a test run, some surfaces associated with bearings within the cutter wheel were found to be damaged due to scuffing - severe sliding wear. There is a static load applied to the surfaces due to gravity. However, the reason for this damaged issue was believed that there is a large dynamic load applied to the surfaces during the excavation. This dynamic load was not found in a previous FE model used to verify safety issues. Therefore, a new FE model that is more in line with reality, and a failure analysis were required. Additionally, a feasibility study for a cutter wheel with a larger dimension was also needed since a larger cutter wheel is desirable. Firstly, wear mechanisms were reviewed, and some theories were chosen to analyze the damaged issue. Since it was unknown whether the surfaces were well-lubricated or not, both cases were investigated. The Archard wear equation was used to analyze the poor-lubricated situation, while the lubrication number and the Reynolds equation were used to analyze the well-lubricated case. Secondly, contact mechanisms between the surfaces were also investigated. The investigation of the contact mechanisms involved several theories, such as the Hertzian contact theory and the impact load factor. Besides these theoretical analyses, a numerical analysis was performed. Lastly, a new FE model was established in Ansys. Both the cutter wheel which was subjected to scuffing(existing cutter wheel), and the cutter wheel with a larger dimension(larger cutter wheel) were analyzed by the use of the new FE model. The maximum and minimum wear rates obtained by the Archard wear equation are approximately 1.9・10-2mm3/m and 4.8・10-3mm3/m, which are considered as a completely unacceptable level in engineering applications. The maximum and minimum critical loads obtained by the Reynold equation are approximately 1.8kN and 24.8kN, which both are larger than the static load applied to the surfaces. The maximum and minimum critical mean contact pressures obtained by the lubrication number are approximately 65MPa and 240MPa, which both are larger than the mean contact pressure generated by the static load. No evidence shows that there is a large dynamic load applied to the surfaces during the excavation. The largest possible contact pressure on the bearings in the existing cutter wheel is very close to the limit of severely damaged. The largest possible contact pressure on the bearings in the larger cutter wheel is believed to exceed the limit of severely damaged. The previous assumption that the surfaces were damaged due to a large dynamic load was wrong. The obtained results support that the surfaces were only subjected to a static load and were damaged due to inadequate lubrication. The existing cutter wheel is operated safely with the current load cases. However, the forward thrust force is suggested to decrease when the cutting angle is large. There is a high risk if the larger cutter wheel is operated with the current load cases.

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The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding. An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage. A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner. A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.   The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction. / civilingenjörsexamen

<p>The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.</p><p>An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.</p><p>A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.</p><p>A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.</p><p> </p><p>The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.</p><p> </p> / civilingenjörsexamen