The lubricants that are applied during metal cutting acts on the interface between the tool and the nascent surfaces generated by the cutting process. Dispersions of oil in water made using suitable emulsifier(s) are used as metal cutting lubricants. The efficiency of the emulsion in rendering a low friction layer on the freshly cut surface will depend on the composition of the emulsion and on the speed, load and temperature characteristics in the tribological system. A unique tribometer which can perform friction testing on freshly cut surfaces has been designed and built for the experimental investigation. In this experimental facility experiments are conducted by performing cutting operation inside a pool of the lubricant and friction force is measured in-situ. Experiments at different loads and speeds were performed. The surfaces were subsequently subjected to spectroscopic analysis using X-ray Photoelectron spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). Lubricity of the base oils on nascent and preformed (oxidized) surfaces are compared by performing friction tests on surfaces which are cut and friction tested without exposing them to the environment, and on surfaces which were cut and exposed to the environment. While the freshly cut surfaces were seen to be sensitive to the structure of the base oil, the oxidized surfaces did not differentiate between the oil structures. Amongst the three base oils tested, aromatic oil was found to exhibit the least friction. This is attributed to tendency of the aromatic chains to react with the surface and form a film, due to the formation of radical anion-metal cation complexes. Results from spectroscopic investigations are presented to substantiate these arguments. The thesis then explores the differences in the tribological behavior promoted by an emulsion between, when it acts on a cut surface and is slid just once, and when it acts on a cut surface slid repeatedly. Due to repeated sliding, friction was found to decrease with sliding time (distance), and the transition from a freshly formed surface to a repeatedly slid one was found to follow a smooth transition. The improvement in lubricity is attributed to the formation of carboxylate type structures (C=O) which get generated due to the tribological action under repeated sliding conditions in the presence of water. Under repeated sliding conditions, the friction as a function of emulsifier concentration is found to exhibit a minimum at a value which is much below the critical micellar concentration of the emulsifier (CMC). However, the variation under continuous cutting followed a different pattern, with the friction undergoing a sharp decrease close to the CMC. The effect of speed on the tribological performance was investigated and friction was found to increase dramatically beyond a critical speed which is marked as the onset of starvation. The characteristic time required for a film to develop on a newly created surface, together with the contact pressure conditions dictated by the load and speed dictates starvation. The films formed at speeds corresponding to starvation conditions was found to have a significantly different chemical structure from that corresponding to a speed less than the starvation speed.. The effect of temperature was found to affect the lubricity adversely. At elevated temperature, the nature of the film was found to change to that to starved condition, even at a speed which does not register starvation when operating at a lower temperature. The effect of solubility of the emulsifier on the friction characteristics were explored by using emulsifiers of varying hydrophilic-lypophilic values (HLB). Lower HLB emulsifiers were found to exhibit lesser friction, than those corresponding to high HLB value. The variation in lubricity is examined in the light of the morphology of the micellar structures which evolve using these emulsifiers. The main conclusions of the thesis are: 1 Evaluation of lubricity of metal cutting fluids warrants a testing strategy which tests their lubricity on freshly cut surfaces. 2 The formation of carboxylate structures aids lubricity while using an emulsion; emulsions which can result in the formation of such structures exhibit better lubricity under cutting conditions. 3 Tribofilms which show characteristic peaks related to chemisorbed oxygen is found to exhibit good lubricity under the test conditions. 4 Emulsifiers which form lamellar micellar structures which aid easy shear give better lubricity in cutting than those which yield spherical micelles.

The diploma thesis is focused on the design and realization of an experimental device. The purpose of device is the simulation of dynamic and kinematic conditions of knee replacement during the walking cycle. The simulator will be used to study the formation of the lubricating film in contact of the femoral component and the polyethylene spacer, and to the cyclic wear tests for knee replacements. First part of thesis is focused on the description of working parameters of knee replacements and analysis of knee joint simulators. The description of conceptual design and selection of the final variation follows. The final design allows simulation of dynamic and kinematic conditions of ISO 14 243-3. Creation of lubricating film is analyzed by the non-contact optical fluorescence microscopy method. The work includes complete drawing documentation, wiring diagram, verification of the functionality of the device and detailed operating instructions.

The submitted master’s thesis describes the development of a tribometer used to measure the adhesion of a real rail. The thesis contains an overview of the basic terms concerning wheel and rail contact. Following that, there is an overview of devicesthat are able to measure the adhesion on a real track. The author's solution includes a design of the tribometer, the proposed measurement methodology and also a description of the individual components. The result of this thesis is a functional device, verified in laboratory conditions and on a real track.

Given diploma thesis deals with the design and realization of a device whose purpose is to simulate real condition in the contact area of deep groove ball bearings. Direct observation of such area was then carried out. Initial part of the thesis addresses principles occurring in ball bearings, such as friction and lubrication and wear mechanisms. Several devices which are commonly used for bearing lubrication studies are then described at the work. Subsequently, author’s solution was introduced with the output of Ball-on-ring device. Ball-on-ring configuration is key feature due to its geometry since it enables to create identical conditions as those which occur in ball bearings such as contact pressure and velocities. Lubricant distribution by the contact area is analysed with fluorescent microscopy. Part of this thesis is a validation experiment and drawing documentation of the device.

No description available.

Para transmitir o torque gerado pelo motor de combustão interna para a caixa de transmissão por meio da embreagem, seja em automóveis ou caminhões, é necessário que haja contato por deslizamento entre um material polimérico multifásico e um contracorpo metálico de ferro fundido cinzento. Além disso, os níveis do coeficiente de atrito entre esses materiais têem que ser suficientemente alto e estável, para proporcionar uma transmissão de torque regular e eficiente. Porém, durante o deslizamento, materiais são transferidos de uma superfície para outra, e alterações microestruturais e fisico-químicas ocorrem. Como consequência, uma nova superfície (denominada de tribofilme) se desenvolve, influenciando o desempenho funcional da embreagem. Dessa forma, compreender as suas características tem se tornado essencial para desenvolver sistemas de embreagens cada vez mais eficientes. No entanto, muitos ensaios são necessários para que se possa entender como uma ou várias matérias primas se comportam em relação aos aspectos tribológicos. Isso faz com que surja a necessidade de repetir os ensaios inúmeras vezes, para que se façam as escolhas mais assertivas tanto das matérias primas quanto dos processos envolvidos. Como alternativa, para reduzir tempo e custos, e ter um maior controle sobre as variáveis de ensaio, busca-se simular em laboratório, com equipamentos mais simples, a reprodução das interações tribológicas em condições reais. A primeira fase deste trabalho tem como objetivo apresentar os mecanismos de desenvolvimento do tribofilme para três níveis de severidade em condições reais de aplicação (ensaios mais demorados, complexos e mais caros, devido à necessidade da confecção completa dos protótipos), e posteriormente correlacionar esses mecanismos com os que foram simulados por meio de ensaios conduzidos num tribômetro de laboratório do tipo pino-disco (ensaios mais rápidos e mais simples, consequentemente menos complexos), variando o PV de 3,08 até 11,08 MPa ms-1. Foi constatado que as características do tribofilme dependem da severidade da aplicação. Além do que, o tribômetro pino-disco (amostra de 13 mm de diâmetro externo) consegue reproduzir os mecanismos identificados em campo, pois houve paridade na transferência das características do tribossistema do modelo de ensaio para o da condição real (430 mm de diâmetro externo). Na segunda fase, diferentes séries de ensaios tribométricos foram realizadas para investigar a influência do tribossistema no desempenho funcional do par tribológico (atrito e desgaste). Para os ensaios tradicionais, foi constatada um aumento na taxa de desgaste para temperaturas superiores a 250°C, revelando uma transição no regime moderado de desgaste para o severo. Quando os debris de desgaste foram removidos do meio interfacial, o nível do coeficiente de atrito aumentou e a taxa de desgaste reduziu. Já a adição de debris de desgaste ao meio interfacial contribuiu para aumentar a taxa de desgaste e reduzir drasticamente o nível do coeficiente de atrito. No entanto, quando os ensaios foram realizados empregando discos pré-condicionados, a taxa de desgaste e o nível do coeficiente de atrito foram otimizados, principalmente em níveis de severidade mais elevados (PV 10,09 MPa ms-1) indicando potencial ganho na eficiência do sistema embreagem. / Torque from an internal combustion-engine to a gear box, either in automobiles or trucks, is transmitted by a clutch system. In order to transmit torque from one side to the other, sliding contact between a multiphase friction material and a gray iron rotor is necessary. Torque transmission depends on the friction level among the tribological couples, and it have to be relatively high and most importantly stable to allow an efficient and regular performance. During the sliding between the coupling surfaces, material is transferred from one surface to the other causing microstructure and chemical changes. As consequence, a new surface, also known as tribofilm, is developed. This surface governs the clutch system performance and understanding the tribofilm characteristics is very important to improve the development of efficient clutch systems. For this, a large number of tests are necessary to understand the tribological behavior of the raw materials. Such investigation is highly empirical and in order to have a consistent data it\'s necessary to carry out several friction tests repetitions. Alternatively, to save time and money, and have better control over the test variables, the real tribological interactions can be simulated in laboratory by using simple equipment, pin-on-disc tribometer. The simplicity of this device allows evaluating a larger number of alternative materials. The first part of this work aims to investigate the tribofilm development mechanisms in three severity levels on the field application (those tests are more time-consuming, complex and expensive, because it is necessary to produce the entire prototype), and then correlate these mechanisms with those simulated in a pin-on-disc tribometer (faster and simpler test) by changing the PV level from 3.08 to 11.08 MPa ms-1. It was found that the tribofilm characteristics depend on the severity of application. In addition, the pin-on-disc tribometer (sample of 13 mm outside diameter) can reproduce the same mechanisms that were identified on the field, due to the parity between the tribosystem characteristics of test model and field condition (430 mm external diameter). In the second part of this work, different series of tribometer tests were performed to investigate the influences of tribosystem on tribological couple performance (friction and wear). Standard tribometer tests presented an increasing in the wear rate at temperatures of 250°C, revealing a transition from moderate to severe wear regime. When wear debris were removed from the interfacial contact, the friction coefficient level increased and wear rate reduced. On the other hand, when the wear debris were added, it contributed to increase the wear rate and to reduce the friction level dramatically. However, when the experiments were performed by using pre-conditioned discs, the wear rate and friction coefficient level has been optimized, particularly at higher severity levels (PV 10.09 MPa ms-1).

This research conducts tribological investigation in three areas. The first area of research is to obtain basic understanding of tribological properties of high performance Inconel alloys. Pin-on-disk testing was conducted through a range of applied normal loads and sliding velocities in an unlubricated condition. Average friction coefficient, friction work, and specific wear rates were calculated from the data and microscopy techniques were used to observe and characterize wear mechanisms. Experimental results show a dependence of average coefficient of friction as a function of frictional work. Also shown is the wear rate dependence on frictional work, predicated by a wear mechanism change. This research gives a tribological baseline for high performance alloys. The second area of research is in the in situ spatial study of friction, complemented by monitoring changes in electrical contact resistance (ECR). Pin-on-disk testing of samples was done under low normal loads and velocities. Friction and electrical contact resistance measurements were taken spatially in the wear track during each friction cycle, giving a spatial evolution of friction and resistance change, in situ. Results show a lowering in the ECR under increased friction cycles, which was closely related to a change in the friction coefficient of the material. Using surface profilometry and X-ray Photoelectron Spectroscopy, we determined that the lowering of resistance is a result of surface modification through wear and development of a friction induced conductive tribo-film. This research provides a simple method for in situ monitoring of friction and solidifies a fundamental relationship between friction and contact resistance. The third area of research is the design of a variable force tribometer, incorporating the fundamental results demonstrated in the first two experiments. The creation of a novel testing apparatus to test materials under dynamic tribological conditions is given in detail. Simple experiments were performed on an Inconel sample and preliminary results show how dynamic normal and tangential forces affect the friction coefficient. These early results utilizing the variable force tribometer will lay the groundwork for more advanced research into the dynamic nature of friction.

Šiame darbe atlikti biologinių tepamųjų medžiagų tribologinių savybių tyrimai bei aptariami gauti rezultatai. Tirtas grynas ir sekančiais priedais modifikuotas rapsų aliejus: stearino rūgštimi, oleino rūgštimi, monogliceridais, monodigliceridais bei jų kompozicijomis. Tyrimų rezultatai rodo, kad rapsų aliejus, modifikuotas įvardintomis medžiagomis bei jų mišiniais, efektyviau slopina dilimą, o trintį mažina efektyviau net už komercines biologines alyvas. Nnustatyta, kad rapsų aliejus modifikuotas oleino rūgštimi geriau slopina dilimą lyginant su grynu rapsų aliejumi. Rapsų aliejaus mišinys su 2% oleino rūgšties ir 0,5% monodigliceridų priedais ne tik užtikrina mažus trinties nuostolius tribosistemoje, bet šie nuostoliai viso standartinio keturių bandymo metu turi tendenciją mažėti. / At this work there are accomplished researches of biological properties of lubricating materials bio-tribological features and disputed obtained results. This work discusses bio-tribological properties of lubricating materials results. Tests were used rapeseed oil additives modified next: stearic acid, oleic acid, monoglycerides, monodiglycerides and their compositions. Investigation shows, that the modification of rapeseed oil substances and mixtures there of effectively inhibits wear and effectively reduces friction, even for commercial bio oil. The investigation revealed that the modified rapeseed oil oleic acid improves friction surfaces to wear protection. It was found that a mixture of rapeseed oil with 2% oleic acid and 0.5% monodiglycerides accessories not only ensure the minimum of friction losses in the moment, but these losses during the test have a tendency to decrease.

Para transmitir o torque gerado pelo motor de combustão interna para a caixa de transmissão por meio da embreagem, seja em automóveis ou caminhões, é necessário que haja contato por deslizamento entre um material polimérico multifásico e um contracorpo metálico de ferro fundido cinzento. Além disso, os níveis do coeficiente de atrito entre esses materiais têem que ser suficientemente alto e estável, para proporcionar uma transmissão de torque regular e eficiente. Porém, durante o deslizamento, materiais são transferidos de uma superfície para outra, e alterações microestruturais e fisico-químicas ocorrem. Como consequência, uma nova superfície (denominada de tribofilme) se desenvolve, influenciando o desempenho funcional da embreagem. Dessa forma, compreender as suas características tem se tornado essencial para desenvolver sistemas de embreagens cada vez mais eficientes. No entanto, muitos ensaios são necessários para que se possa entender como uma ou várias matérias primas se comportam em relação aos aspectos tribológicos. Isso faz com que surja a necessidade de repetir os ensaios inúmeras vezes, para que se façam as escolhas mais assertivas tanto das matérias primas quanto dos processos envolvidos. Como alternativa, para reduzir tempo e custos, e ter um maior controle sobre as variáveis de ensaio, busca-se simular em laboratório, com equipamentos mais simples, a reprodução das interações tribológicas em condições reais. A primeira fase deste trabalho tem como objetivo apresentar os mecanismos de desenvolvimento do tribofilme para três níveis de severidade em condições reais de aplicação (ensaios mais demorados, complexos e mais caros, devido à necessidade da confecção completa dos protótipos), e posteriormente correlacionar esses mecanismos com os que foram simulados por meio de ensaios conduzidos num tribômetro de laboratório do tipo pino-disco (ensaios mais rápidos e mais simples, consequentemente menos complexos), variando o PV de 3,08 até 11,08 MPa ms-1. Foi constatado que as características do tribofilme dependem da severidade da aplicação. Além do que, o tribômetro pino-disco (amostra de 13 mm de diâmetro externo) consegue reproduzir os mecanismos identificados em campo, pois houve paridade na transferência das características do tribossistema do modelo de ensaio para o da condição real (430 mm de diâmetro externo). Na segunda fase, diferentes séries de ensaios tribométricos foram realizadas para investigar a influência do tribossistema no desempenho funcional do par tribológico (atrito e desgaste). Para os ensaios tradicionais, foi constatada um aumento na taxa de desgaste para temperaturas superiores a 250°C, revelando uma transição no regime moderado de desgaste para o severo. Quando os debris de desgaste foram removidos do meio interfacial, o nível do coeficiente de atrito aumentou e a taxa de desgaste reduziu. Já a adição de debris de desgaste ao meio interfacial contribuiu para aumentar a taxa de desgaste e reduzir drasticamente o nível do coeficiente de atrito. No entanto, quando os ensaios foram realizados empregando discos pré-condicionados, a taxa de desgaste e o nível do coeficiente de atrito foram otimizados, principalmente em níveis de severidade mais elevados (PV 10,09 MPa ms-1) indicando potencial ganho na eficiência do sistema embreagem. / Torque from an internal combustion-engine to a gear box, either in automobiles or trucks, is transmitted by a clutch system. In order to transmit torque from one side to the other, sliding contact between a multiphase friction material and a gray iron rotor is necessary. Torque transmission depends on the friction level among the tribological couples, and it have to be relatively high and most importantly stable to allow an efficient and regular performance. During the sliding between the coupling surfaces, material is transferred from one surface to the other causing microstructure and chemical changes. As consequence, a new surface, also known as tribofilm, is developed. This surface governs the clutch system performance and understanding the tribofilm characteristics is very important to improve the development of efficient clutch systems. For this, a large number of tests are necessary to understand the tribological behavior of the raw materials. Such investigation is highly empirical and in order to have a consistent data it\'s necessary to carry out several friction tests repetitions. Alternatively, to save time and money, and have better control over the test variables, the real tribological interactions can be simulated in laboratory by using simple equipment, pin-on-disc tribometer. The simplicity of this device allows evaluating a larger number of alternative materials. The first part of this work aims to investigate the tribofilm development mechanisms in three severity levels on the field application (those tests are more time-consuming, complex and expensive, because it is necessary to produce the entire prototype), and then correlate these mechanisms with those simulated in a pin-on-disc tribometer (faster and simpler test) by changing the PV level from 3.08 to 11.08 MPa ms-1. It was found that the tribofilm characteristics depend on the severity of application. In addition, the pin-on-disc tribometer (sample of 13 mm outside diameter) can reproduce the same mechanisms that were identified on the field, due to the parity between the tribosystem characteristics of test model and field condition (430 mm external diameter). In the second part of this work, different series of tribometer tests were performed to investigate the influences of tribosystem on tribological couple performance (friction and wear). Standard tribometer tests presented an increasing in the wear rate at temperatures of 250°C, revealing a transition from moderate to severe wear regime. When wear debris were removed from the interfacial contact, the friction coefficient level increased and wear rate reduced. On the other hand, when the wear debris were added, it contributed to increase the wear rate and to reduce the friction level dramatically. However, when the experiments were performed by using pre-conditioned discs, the wear rate and friction coefficient level has been optimized, particularly at higher severity levels (PV 10.09 MPa ms-1).

Dans des conditions de conduite dite douce, la bande de roulement de pneumatique présente des faciès d’usure de type cratères d’usure ou bien des rides.Le but de ce travail de thèse était de recréer et d’étudier ces faciès d’usure pour des élastomères renforcés par du noir de carbone ou de la silice sur un tribomètre rotatif afin de pouvoir expliquer leurs mécanismes de formation. Des parallèles ont été établis entre les valeurs de perte de masse, de coefficient de frottement et le type du faciès d’usure tout en prenant en compte les propriétés physico-chimiques des échantillons.L’étude a expliqué les différences entre les types de faciès d’usure générés sur des matériaux renforcés par du noir de carbone et ceux renforcés par de la silice. Les paramètres influant sur a transition cratères d’usure et rides ont également été étudiés. / In soft conditions of driving, wear patterns appear on the tire tread. They are called wear craters and ridges.The aim of this thesis work was to recreate and to study these wear patterns for reinforced elastomers by carbon black or silica on a rotary tribometer in order to explain their mechanisms formation. Parallels were established between the values of mass lost, friction coefficient and the type of wear patterns while taking into account the physico-chemical properties of samples.The study explained the differences between the type of wear patterns generated on reinforced materials by carbon black and those reinforced by silica. Affect parameters on the transition between wear craters and ridges were also studied.