Eaton Analysis of Face Seal Contacts

Eaton Corporation has tasked Seal Team Fix with the challenge of obtaining the material properties of the carbon compounds used in their face seals and creating a service life prediction model of their seals based on this material property data. Eaton is a worldwide power management company with a multidisciplinary business portfolio. This project pertains to Eaton\u27s Aerospace division, and in particular the carbon face seals in gas turbine engines and gearboxes. This preliminary design report demonstrates the research, design and analysis leading to a final conceptual decision as to how a carbon face seal life prediction model will be created. This model would allow for the justification of Eaton to purchase the more cost-effective product between three manufacturer\u27s supplying similar carbon grades. Once a clear problem definition of the project had been established, each member of Seal Team Fix developed 30 different design concepts in accordance with the Capstone Design Project requirements. While a small number of these original design concepts would play into our final proposed design, there were still important pieces to our necessary analysis which were overlooked. With the help of our Technical Adviser Dr. D.M.L. Meyer, we were able to conclude our final engineering approach. Our final engineering approach consists of a three part process, each of which contains multiple studies. This three part process involves a failure mode study, characterization of materials, and finally the prediction model. The failure mode study consists of stress analyses, and pin on at testing while measuring the roughness values of the carbon materials incrementally. The characterization of materials will consist of hardness testing of the material as well as obtaining the coefficients of friction and wear rates from tribometer testing. The prediction model will consist of calculating the leakage rate of the seals as a function of their roughness values as well as the radius of the seals and using the data gathered through experimentation to create a final prediction model in Microsoft Excel

Uncertainty Analysis of a Multifunctional Tribometer

In response to the high cost and limited instrumentation available on commercial tribometers a student designed tribometer was conceived, built, and tested. This tribometer combines multiple tribology testing configurations into a single compact and reconfiguration tribometer, dubbed the multifunctional tribometer. This tribometer is also capable of operating in expanded experimental spaces not covered within the limited scope of industry standardized tribological tests. Specifically, this tribometer is able to conduct rotary tests in a reciprocating fashion; this capability is unavailable on any other tribometer published so far in literature or available commercially. Following an overview of the industry standards and the tribometer’s capability is an uncertainty analysis for the reciprocating block on ring testing regime of the multifunctional tribometer. As this test method is totally unique to this machine it is necessary to prove its validity and accuracy. This is done through the use of an uncertainty analysis which is then expanded across all experimental spaces covered by the testing configuration. Additionally, an uncertainty budget has been made which shows what aspects of the machine would be most worthwhile to upgrade to improve performance. Finally, a case study is included which involves an experiment testing the lubrication properties of WD40 in this reciprocating block on ring configuration of the multifunctional tribometer

Tribological investigations of the piston assembly and liner of a gasoline engine

The automotive industry is being forced towards greater efficiency, increased engine power from smaller engines and lower environmental impact by both governmental legislation and public opinion. Oil drain intervals are increasing whilst emissions legislation limit the use of current wear protection and antioxidant additives containing elements such as phosphorus and sulphur. To address these demands and challenges an increased understanding of the link between lubricant degradation, its transport and residence time, and the effect on piston assembly tribology is required. The aim of the work reported in this paper was to further develop the understanding of the effect degraded lubricants have on piston assembly tribology. The small oil volumes and environmental conditions in the piston assembly make the affective lubrication and protection of components in this region one of the most challenging areas of tribology. This was carried out through an extensive experimental programme using a research engine, tribometer testing and chemical and rheological analysis of lubricant samples

An environmental tribometer for the study of rubbing surface reactivity

A new tribometer was designed to study the reactivity of rubbing surfaces under controlled environmental conditions. The contacting samples are isolated from the atmosphere by a chamber under secondary vacuum (10−6 mbar) where reactive gasses can be injected. The sample chamber can also be heated up to 900 ◦C by a radiative furnace. The sliding velocity can be varied from 0.05 to 1.5 m/s and the applied load from 5 to 100N (contact pressure ranged between 130MPa and 1.3 GPa). The instrumentation of the tribometer enables continuous measurement of the normal and tangential forces, vertical displacement of the contacting samples, temperature in the vicinity of the contact zone, partial pressure and gas composition in the test chamber and electrical contact resistance. The design difficulties have been exposed and the chosen technological solutions are presented. A test has been carried out to validate the tribological device

Computational Modeling of Transient Processes During Run-In for Tribological Systems

Understanding the frictional behavior of machine elements in mutual rolling or sliding contact is important for many engineering applications. When frictional sliding is initiated, the tribological system passes through several stages with each stage possessing its own unique frictional property. The initial transition process preceding stationary sliding is usually called “run-in”. During the run-in time interval, surface topographies of frictional contacts as well as lubricant distribution and surface tribofilms reorganize and adjust through asperity deformation and wear processes before reaching the steady state. This surface stability formed during run-in leads to an improvement in frictional performance during steady state operation, which increases equipment life and efficiency. Thus, understanding of the frictional transient process and optimizing the time schedule required for the run-in of equipment such as for aircraft engines and naval vessel gas turbines can lead to improved solutions for more desirable operating conditions for the lifetime of the equipment. This thesis investigates the running-in of both lubricated and unlubricated frictional contact in order to gain insight into how friction changes during this time interval. For lubricated friction, it is shown that the surface topography and lubricating fluid goes through a self-organization process during run-in caused by frictional mechanisms that change the surface topography and removes fluid from the area of contact until friction and wear at the interface reaches its equilibrium value. For unlubricated friction, three common tribo-mechanical systems undergoing dry sliding during run-in are investigated: the pin-on-disk, a journal bearing, and a piston-cylinder system. Using computer simulation, a transient frictional response curve is presented for various frictional conditions in order to gain insight into how the frictional value changes during run-in. It is shown that adjustment of the static coefficient of friction can dramatically affect the response behavior with higher coefficient of friction values resulting in higher frictional forces and longer times to reach equilibrium, while smaller values shorten time to equilibrium and reduce frictional forces. These discoveries suggest seeking ways to optimize the materials in order to optimize the transient friction during run-in which are summarized in the conclusion

A tribological investigation of windscreen wiper performance

This project focused on understanding windscreen-wiper/glass interactions with an aim to reduce friction and wear, improve wiping quality and prevent friction induced vibration, (also known as squeak). To achieve this, the contact between windscreen and wiper was simulated under laboratory conditions using a UMT2 Tribometer, which loaded a stationary rubber profile against a rotating glass disc. Then, a range of measurement and analytical techniques were used to characterize the effect of conditions on different aspects of wiper performance. Different surface conditions were reproduced by applying a range of common treatments to the glass, including hydrophobic and hydrophilic coatings. In addition to this, a new method of partially forming self-assembled monolayers was devised in order to produce test specimens with a controlled range of surface energies. It was shown that friction reduces with increasing surface energy, which is attributed to a smaller volume of water being entrained into the contact. Following this, a range of non-steady state friction behaviours were studied. These included combined friction and wear tests, where under severe conditions it was shown how friction performance is dominated by the formation and removal of burs, which prevents water from being entrained into the contact. In addition, drying tests were conducted to understand “tacky” behaviour (i.e., the peak in friction peak under partially lubricated conditions). This was shown to be controlled by decreasing the surface tension of the water, through the addition of detergent, and provided evidence to support the theory that water menisci are responsible for increasing surface area. Static friction behaviour was also investigated, and the effects of start-up velocity and stationary duration on friction were quantified and explained. The practical implications of these results are discussed in terms wiper design and material selection. To study friction induced vibration, (FIV), friction, sound and high speed video measurements were combined with finite element modelling of a rubber wiper/glass contact. In agreement with previous research, FIV only occurs when the friction versus speed curve has a negative gradient; a factor, which, in combination with the low stiffness of the materials, can lead to vibrational instabilities in the mixed regime. Results also showed that friction induced vibration is strongly affected by surface condition, and only occurs for a certain range of surface energies. This is explained by the fact that both high and low surface energies alter the gradient of the Stribeck curve thereby preventing FIV (i.e., low surface energies prevent sufficient liquid entering the contact and high surface energies attract water molecules to the surface of the glass producing a film that reduces friction). In order to study the source of squeak, simultaneous measurements were realised by a high speed camera, microphone, and laser Doppler vibrometer (LDV). This showed that although both the wiper and glass vibrate with the same frequency, it is the latter that transmits sound to the air. Results from the high-speed camera and microphone have shown that the frequency of the rubber vibration equals to the frequency of the emitted sound and the water vibration. This frequency is the same as the eigen frequencies determined from a finite element model of the wiper, which was developed. These observations led to the conclusion that friction induced noise occurs only when bending modes of the wiper are excited and this has important implications for the control of FIV since it shows that emitted sound can be eliminated by modifying the blade geometry during the design stage. Another important observation is that the frequency of squeak decreases with increasing volume of water present on the glass. This is attributed to the water effectively adding mass onto the vibrating system and hence reducing its natural frequency. Additionally, capillary waves have been for the first observed in the water surrounding the wiper contact. Based on the understanding gained, a number of recommendations are made regarding means of reducing windscreen wiper noise. Finally, in order to monitor the wiping performance of the rubber wiper, a fluorescence microscopy technique was developed to view the sliding contact. This has enabled the fluid film thickness within the blade/glass contact to be assessed and also manufacturing defects, such as notches and inclusions, to be identified as the cause of wipe quality issues, such as hazing and hairlines.Open Acces

A Study of Walkway Safety and Evaluation of Tribological Test Equipment

A walkway tribometer measures the coefficient of friction between flooring material and a test foot. The value of the coefficient of friction is an indicator as to whether the flooring surface is slippery and has a propensity to cause slip and falls. This study determined that one style of tribometer, an XL Tribometer, mimics the heel-to-floor interaction of the human heel strike. High speed video footage revealed that the test foot strikes the surface and rotates so that full engagement occurs before sliding thus mimicking the affect of a human ankle. The test foot accelerates forward as would be expected during a human slip event. The manufacturer’s reported impact speed of 11 in/s, when set to the operating pressure of 25psi, was found to be much lower than measured speeds of three calibrated tribometers. Three XL tribometers were tested and provided a range of impact speeds from 17.4 to 22.7 in/s (n=540) when set to the operating pressure of 25 psi. The pressure setting was found to have a significant effect on the impact speed while the mast angle had an insignificant affect. A review of human walking studies revealed a range of pedestrian heel impact speeds on the order of 19.4 to 45.3 in/s during normal human ambulation activities. These tribometers fell on the low side of this speed range. A sensitivity study showed that the measured value of the coefficient of friction tends to decrease with a higher impact speed. This COF decrease was on the order of 0.02 and below the machine resolution and considered inconsequential within the walkway safety community

Implementation of a triboelectrical workstation for the investigation of the influence of electrical current on the tribological properties of thin films

Con el fin de hacer que las máquinas, circuitos electrónicos o contactos eléctricos para diversas aplicaciones, funcionen correctamente; es necesario conocer sus características. La mayoría de las máquinas desarrolladas o dispositivos electrónicos están formados por varios componentes que están interconectados. Cuando estos componentes interactúan entre sí o con el medio ambiente, están sometidos a estrés, fricción y desgaste. Por lo tanto, se requiere predecir el comportamiento de estos materiales cuando están sometidos a fricción y desgaste para así tener una interpretación adecuada de lo que ocurre en estos puntos de contacto. La presente tesis se centra en la caracterización de materiales por medio de un sistema tribológico basado en un "punto plano-contacto", donde una bola estacionaria hace de punto y el material de muestra se hace oscilar debajo. Con este sistema es posible determinar el valor de la fuerza tangencial y la fuerza normal, y a partir de estos dos, se puede calcular el coeficiente de fricción. Además, apoyamos el análisis de materiales mediante una caracterización eléctrica en paralelo durante el experimento. Para este propósito, una corriente se inyecta en la muestra. Luego, la caída de tensión y la corriente son medidas y con estos datos, la resistencia eléctrica se puede determinar. El sistema de medición está controlado por un ordenador central que usa LabVIEW y los datos medidos son almacenados para su posterior análisis.Tesi

A New Method of Semi-automated Measurement of Shear Friction Coefficient

The paper is intended for engineer laboratory teaching and measurements in production engineering. The aim is a new method of measuring using the semi-automated measuring set and presenting the results of static shear friction coefficients and kinetic shear friction coefficients, depending on the relatively low speeds of the uniform translational movement of the body. In the framework of a specific engineering task, the methodological questions concerning the interpretation of measurement results in the context of engineering physics and its teaching are solved