While there has been substantial body of work in the field of journal bearing research, much of it is today theoretical or simulated due to today’s computing power. Scania produces experimental data from motor testing, but these are expensive and time consuming. Furthermore there is a difficulty in keeping a sufficiently controlled environment, which at times makes it hard to draw conclusions from testing results. They therefore wish to develop a test-rig which can evaluate friction and wear in journal bearings. This thesis is a continuation of a project in the course Advanced Machine Design given at KTH Royal Institute of Technology. During this thesis the test-rig has been manufactured, built, and evaluated. Furthermore software for the test-rig was developed. Information on journal bearings, risk assessment and signal noise handling were sought. Mechanical development was done with Autodesk Inventor, while Matlab was used for software development. Factorial design was utilised when designing tests and compared to a simple theoretical model. Test results showed promising results for Stribeck curve-producing tests, with good resemblance to known frictional values and trends. Furthermore the test-rig showed good repeatability for replicated tests and produced wear on the bearing shells used. During a prolonged test, the shaft and support-bearings were damaged and requires servicing to be in an operational state. The test-rig requires to be further verified, but the tests that were carried out showed valuable and reliable information on wear and frictional values. Keywords: journal bearing, hydrodynamic lubrication, wear, start-stop, test-rig / Även om en betydande mängd forskning inom glidlager och fullfilmslager har genomförts så är med dagens datorkapacitet en stor del av resultaten numera teoretiska eller simulerade. Medan Scania producerar experimentella resultat, så är dessa dyra och tidskrävande. Vidare är det ibland svårt att hålla en tillräckligt kontrollerad miljö för att dra slutsatser från proverna. Med en dedikerad testrigg som kan tillförlitliga resultat tas fram billigare och snabbare. Detta examensarbete är en fortsättning av kursen Avancerad Maskinkonstruktion som ges vid Kungliga Tekniska Högskolan. Under detta examensarbete har testriggen tillverkats, byggts och utvärderats. Vidare har programvara för testriggen utvecklats. Informationssökning gjordes på glidlager, fullfilmslager, riskbedömning och signalbrushantering. Mekanisk utveckling har gjorts i Autodesk Inventor, medan Matlab användes för mjukvaruutveckling. Faktorial design har nyttjats vid utformningen av tester. Resultaten jämfördes med en enkel teoretisk modell. Testresultaten visade lovade resultat för Stribeck kurva-producerande tester, med god likhet till kända friktionsvärden och trender. Testriggen visade god reproducerbarhet vid replikerade tester. Testriggen producerar slitage på samtliga testade lagerytor. Under ett längre test så har axel och stödlager skadats, varför service behövs för att testriggen skall vara i brukbart skick. Testriggen kräver ytterligare verifiering, men resultaten från de prov som genomförts visar att test-riggen ger värdefull och tillförlitlig information om slitage och friktion kunna utrönas. Nyckelord: glidlager, hydrodynamisk smörjfilm, nötning, start-stop, testrigg

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This dissertation is focused on experimental study of lubricant film behavior under transient conditions. For real machine parts such as gears, roller bearings and cam mechanism the operating conditions such as speed, load and radius of curvature of rubbing surfaces are vary during the working cycle. Change in operating conditions may pose an increased risk of the lubricating film breakdown. Direct contact of rubbing surfaces at the time of the lubricating film breakdown causes an increase in friction and wear. The high-speed CMOS camera was used to record the dynamic changes in lubricating film thickness during the experiment. The optical interferometry method has been used for reverse reconstruction of lubricating film thickness of the recorded interferograms. It was confirmed that the operating parameters have a major impact on the formation of lubricant film and its thickness and a certain combination of boundary conditions can cause lubricating film rupture. The obtained results showed, that modified topography of the rubbing surfaces can help to increase the lubrication film thickness especially in critical phases of working cycle.

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Mechanical face seals, MFS, are important machine components in the heavyduty-vehicle industry which generate a high frictional power loss. In order to lower these losses an investigation has to be performed on the frictional behavior of the MFS. A physical test rig allows an evaluation of existing seals and new concepts to compare their performances. Prior to this project, a test rig for MFS had been partially designed and manufactured by a group of students within a design project at KTH. This report presents the continuation of this work. A solid background study was performed in which the best testing equipment and theoretical models in the literature to characterize MFS were reviewed. The design and manufacturing of the test rig prototype has been completed and most importantly, it has been validated, achieving an acceptable assessment of repeatability. Tests have been planned and executed to assess the repeatability of the test rig and to study the effect of different parameters: speed, preload, eccentricity and angular misalignment. A theoretical loss model was performed which gave discrepant results for studies with mixed lubrication, making a comparison with the experiments impracticable. Further work has to be done to evaluate the applicability of the proposed model. In addition, a valuable Matlab tool has been developed and packaged to facilitate processing data of the test rig for future users. / Mekaniska glidringstätningar är viktiga maskinkomponenter inom tung fordonsindustri, men de orsakar höga friktionsförluster. För att sänka dessa förluster behöver först en undersökning utföras för att få förståelse för friktionsbeteendet hos de mekaniska glidringstätningarna. En fysisk testrigg gör det möjligt att utvärdera befintliga tätningar och jämföra deras prestanda med nya koncept. Denna rapport är en uppföljning på ett koncept av en testrigg för mekaniska för glidringstätningar som en grupp studenter på KTH tidigare tagit fram. Innan detta projekt hade en testrigg för konceptet delvis utformats och tillverkats. Fortsättningen av detta arbete innebar att en heltäckande bakgrundsundersökning utfördes samt även en granskning av teoretiska modeller för att karakterisera tätningarna. Konstruktion och tillverkning av den tidigare testriggen slutfördes. Dessutom validerades testriggen vilket visade att dess repeterbarhet var accepterbar. Tester planerades och utfördes för att studera effekten av följande parametrar: hastighet, kast, excentricitet och snedställning. En teoretisk förlustmodell utvecklades men visade sig ge avvikande resultat för blandsmörjning vilket gjorde jämförelser med experimenten ogenomförbara. Ytterligare arbete bör göras för att utvärdera tillämpligheten av den framtagna modellen. Utöver detta har även ett användargränssnitt i Matlab utvecklats och paketerats för att underlätta för framtida användare att bearbeta data från testriggen.

During the production of metal zippers, cemented carbide (CC) tools are used to cut preformed brass wire into small elements. Even though the cemented carbide is much harder than the copper alloy, it gets worn and eventually the tool must be replaced. This wear mechanism, which allows soft copper alloys to gradually wear hard CC, must be better understood in order to extend tool life. The mechanism is believed to be tribochemical, as oxides have been found on the surface of the wear mark. Given that most metals oxidize in the presence of oxygen, it is relevant to examine if oxidation of tungsten carbide and cobalt contribute to the wear. The purpose of this work has been to study the influence of oxygen availability on the slow wear of cemented carbides during copper alloy processing. A simplified sliding test rig, developed in a previous study, was used. A small CC cylinder slid against a large rotating copper or brass cylinder in a “crossed cylinders” configuration. The point of contact was encapsulated by a 3D-printed cover. Some tests were done in an oxygen deficient atmosphere, where the cover was continuously filled with flowing nitrogen gas. One test was performed with compressed air flowing through the cover, and one was performed without flowing gas. The wear marks on the CC cylinders were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and optical profilometry. The wear volume of these marks was also calculated. SEM pictures showed that both brass and copper transferred to the cemented carbide. When the test was performed with brass, zinc oxide was found in the wear mark. When it was performed with copper, no oxide was found.

The excellent lubrication present within mammalian synovial joints attracted scientific interest, and some close-to-realistic models were applied to study the mechanism in vitro. In this project, the synergistic lubrication of synovial fluid was investigated by using 1,2-Dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), hyaluronic acid (HA), and phosphate-buffered saline (PBS buffer) to mimic the synovial fluid. Lubrication by the model synovial fluid was studied using borosilicate glass specimens in Mini-Traction Machine (MTM). The experiments proved that the DPPC vesicle solution and mixed DPPC/HA solution had excellent lubrication ability, stemming both from adsorption of a lubricious layer at the surface of glass specimens and from presence of material reservoir available for repair of wear defects in the lubricious layer. Comparing the macroscale results obtained in this project by MTM with the results in previous studies on microscale by using AFM, we concluded that the microscale study of synergistic lubrication could predict macroscale results, even though some differences were detected due to limited possibilities for exact replication of experimental conditions at the two scales.

High-Frame-Rate Oil Film Interferometry Jonathan Charles White This thesis presents the design and implementation of a high-frame-rate oil film interferometry technique (HOFI) used to directly measure skin friction in time dependent flows. Experiments were performed to determine the ability of a high-speed camera to capture oil film interferometry images. HOFI was found to be able to capture these interferometry images at frequencies up to 105 Hz. Steady laminar and turbulent flows were tested. Transient flows tested consisted of a wind tunnel ramping up in velocity and a laminar boundary layer which was intermittently tripped to turbulence by puffing air out of a pressure tap. Flow speeds ranged from 0 to 108 ft/sec and 10 and 50 cSt Dow Corning 200 dimethylpolysiloxane silicone oil was used. The skin friction was determined from the rate of change of the height of the oil film using lubrication theory. The height of the oil film was determined from the high speed camera interferogram images using a MATLAB script which determined fringe spacing by fitting a four-parameter sine wave to the intensity levels in each image. The MATLAB script was able to determine the height of the oil film for thousands of interferogram images in only a few minutes with sub-pixel error in fringe spacing. The skin friction was calculated using the oil film height history allowing for the direct measurement of skin friction in time dependent flows.

In recent times, there has been an increased interest in replacing conventional metals and synthetic fiber composites in various automobile parts with natural fiber polymer composites. These natural fiber composites offer benefits over conventional materials in terms of reduction in weight, lower cost, comparable high specific properties such as specific stiffness and strength, low abrasion property, and availability of these materials. Environmetal concerns and the need to make eco-friendly materials also encouraged the use of natural fiber polymer composites (NFPC) for various automotive applications, as their usage reduces the emission of harmful pollutants, thereby providing a safer and cleaner environment. The reduction in weight of these materials also helps to reduce fuel consumption in cars. Therefore, this study focused on the investigation and characterization (mechanical, thermal, and tribological) of hemp fibers reinforced polypropylene made with virgin (Biolite) and recycled (Revo) composites, consisting of different fiber loadings from 10% to 30% for possible automotive applications. The result showed an improvement in the compressive properties of the composite as hemp fiber loading increases, with the recycled composite exhibiting a better compression performance in comparison to virgin composites. Revo 41 had the best compressive strength  and a 35% higher value than Biolite 2 of the same hemp fiber loading. However, there was a decrease in the fracture toughness of the composites as hemp fiber loading increases. This was more significant at about 27% from Biolite 1 to Biloite 2, Revo 41 experienced a slight improvement of 15% in fracture toughness with 20% hemp fiber loading. Revo 35 composite which had more degradation steps showed the best thermal performance at low temperature region with a degradation temperature of 276°C, while Biolite 1 at 444°C exhibited the best thermal stability at high temperature degradation. In comparing the tribological behavior of pure polypropylene with the composites, the composites exhibited a better tribological performance as there was a slight decrease in the coefficient of friction and wear rates of composites as the hemp fiber loading increases. Revo 41 of 20% hemp fiber fiber loading had the best wear performance. Considering its strength and slightly better tribological performance, Revo 41 is considered the best performing composite for automotive applications in comparison to the other composites.

No description available.