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1
Algodi, Samer Jasim Mahmood. "Characterisation, modelling and tribological investigations of nano-structured TiC-based electrical discharge coatings." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/55168/.
Повний текст джерелаАнотація:
Electrical discharge coating (EDC) is a surface modification process used to produce hard coatings from a sacrificial powder metallurgy (PM) tool electrode onto a target workpiece. However, the integrity of as-processed EDC surfaces, as reported on in literature, is generally poor, with limited understanding of the fundamental interactions between energy source and workpiece material, and the microstructural development of the surfaces created. This thesis explores, at the nano-scale, the deposition and microstructural development of ED processed cermet coatings. Emphasis is given to TiC-based ED coatings, prepared using a semi-sintered TiC tool electrode. A comprehensive study of TiC/Fe cermet coating microstructural development, as a function of ED processing conditions (current 2 - 19 A; pulse-on time 2 - 64 μs) is presented, using the combined characterisation techniques of scanning electron microscopy (SEM) / energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and cross-sectional transmission electron microscopy (TEM). The ED coatings were composites in nature, with complex banded nanostructures of TiC grains within an Fe matrix. Preferred TiC/Fe ED coatings on 304-SS, achieved under conditions of low processing energy (10 A current and 8 μs pulse-on time), exhibited low levels of cracks and porosity, with hardness values of ~ 1800 HV. The fraction of energy transferred to the workpiece, Fv, as a consequence of ED sparking, is an important parameter which affects directly individual crater geometry and the microstructural development of the near surface modified layer. Hence, a 2D transient heat transfer model is presented, using finite difference methods, and used to estimate effective values for Fv as a function of processing conditions, and thereby to predict coating layer thicknesses of developed microstructures through appropriate consideration of heat flow into the system. The model is validated against previous work in literature and with experimental observations. The modelling demonstrated a variation of energy transferred to the workpiece, of 17 - 23% for increasing current from 2 - 19 A at fixed pulse-on time of 8 μs; and 7 - 53% for increasing pulse-on time from 2 - 64 μs at fixed current of 10 A. Predictions for heat transfer and the cooling of melt pools, arising from single spark events, compared well with experimental observations for the development of these TiC/Fe cermet microstructures. The cooling phase had two distinct stages, with initial rapid non-uniform cooling within the first ~ 10 - 20 μs leading up to the onset of TiC crystallisation, followed by a more uniform stage of heat loss up to ~ 100 μs, leading up to the onset of Fe matrix solidification. The tribological behaviours of TiC/Fe ED cermet coatings on both HSS and 304-SS substrates were investigated, with reference Cu EDM surfaces. The wear resistance of these cermet coatings, on both substrate types, yielded dry sliding wear resistances up to two orders of magnitude greater than that of the substrate. Further, EDC cermet coatings on HSS were typically 2 - 4 times more wear resistant, depending on loading, than those deposited on 304-SS, with wear performances reflecting the composite nature of the coatings coupled with the mechanical properties of the substrates. Laser surface treatments, used to improve the surface integrity of the as-deposited coatings, through the elimination of cracks and porosity, acted to increase the wear rate for all samples, with the exception of coatings on HSS under conditions of high loading. The general increase in wear rate was attributed to a significant reduction in the proportion of TiC within the ED coatings, after laser treatment, combined with an increase in grain size; whilst improvements to the wear performance of laser treated, cermet coated HSS, under high loading, was attributed to the avoidance of an abrasive wear mechanism.
2
Fu, Xi-Yong. "Tribological characteristics of metallic glass in sliding contact : experimental investigations and molecular dynamics simulations /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu148820427653207.
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3
Holzer, Achill, Stephan Koß, Gunnar Matthiesen, Daniel Merget, Stephan Ziegler, Johannes Henrich Schleifenbaum, and Katharina Schmitz. "Tribological investigations on additively manufactured surfaces using extreme high-speed laser material deposition (ehla) and laser powder bed fusion (LPBF)." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71080.
Повний текст джерелаАнотація:
Today's economic and ecological directives demand for highly sustainable machine parts by low production cost and energy consumption. Consequently, it is crucial to guarantee a long service life by protecting all components against wear and corrosion. However, hydraulic components always include stressed surfaces, which suffer from heavy loads at high relative speeds. To prevent fretting, coating processes like thermal spraying or hard chrome have a long history in the field of hydraulics. New additive laser-based processes like EHLA and LPBF offer the potential to apply new coatings without environmentally hazardous substances such as chromium or to manufacture complex parts with new functionalities. So far, additively manufactured surfaces with relative movements are post-processed to obtain surface qualities similar to subtractive methods, as the tribological properties of additive surfaces have not been investigated to date. Therefore, this paper investigates the frictional behavior of 316L surfaces produced by laser-based EHLA and LPBF processes using a disc-disc tribometer.
4
Bansal, Dinesh Gur Parshad. "Tribological investigation of electrical contacts." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31749.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Streator, Jeffrey; Committee Member: Blanchet, Thierry; Committee Member: Cowan, Richard; Committee Member: Danyluk, Steven; Committee Member: Neu, Richard; Committee Member: Thadhani, Naresh. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Stone, D’Arcy S. "Silver Tantalate: a High Temperature Tribological Investigation." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700025/.
Повний текст джерелаАнотація:
As technology advances, mechanical and electrical systems are subjugated to intense temperature fluctuations through their service life. Designing coatings that operate in extreme temperatures is, therefore, a continuing challenge within the tribology community. Silver tantalate was chosen for investigation at the atomic level, the physical and chemical properties that influence the thermal, mechanical, and tribological behavior for moving assemblies in high temperature tribological applications. By correlating behavior of internal physical processes to the macro tribological behavior, the tribological community will potentially gain improved predicative performance of solid lubricants in future investigations. Three different approaches were explored for the creation of such materials on Inconel substrates: (1) powders produced using a solid state which were burnished on the surface; (2) monolithic silver tantalate thin films deposited by magnetron sputtering; and, (3) an adaptive tantalum nitride/silver nanocomposite sputter-deposited coating that forms a lubricious silver tantalate oxide on its surface when operated at elevated temperatures. Dry sliding wear tests of the coatings against Si3N4 counterfaces revealed friction coefficients in the 0.06 - 0.15 range at T ~ 750 °C. Reduced friction coefficients were found in nanocomposite materials that contained primarily a AgTaO3 phase with a small amount of segregated Ag phase, as suggested by structural characterization using X-ray diffraction. The presence of nanoparticles of segregated Ag in the thin films further enhanced the performance of these materials by increasing their toughness. Additional characterization of the AgTaO3 films at 750 °C under normal loads of 1, 2, 5, or 10 N revealed that the friction monotonically increased as the load was increased. These results were complemented by molecular dynamics simulations, which confirmed the increase of friction with load. Further, the simulations support the hypothesis that this trend can be explained in terms of decreased presence of Ag clusters near the sliding surface and the associated decreased porosity. The results suggest that the relative amount of Ag in a TaN or Ta2O5 mastrix may be used to tune film performance for a given application.
6
Wang, Zhongnan. "Tribological investigation for next-generation polymeric micro-systems." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/91016/.
Повний текст джерелаАнотація:
The development of micro-fabrication processes for 3D microstructures has led to the production of low-cost, low-energy devices at millimeter scales known as MEMS for a wide range of electronic, mechanical, mechatronic and biomedical applications. As surface-to-volume ratio increases drastically with decreasing dimension, surface properties of the materials are the prominent factor at the interface between two solids and consequent tribological issues such as adhesion, friction and wear will arise in MEMS devices when surfaces are in, or have the potential for, sliding contact. Measurement techniques and principles used in micro-tribology are quite different from those in macro-tribology. Various specialized micro-tribometers have attracted recent attention in attempts to obtain consistent, accurate tribological measurements that could provide information for the design of MEMS components. However, even these have operational parameters quite different to those in the regime typical of MEMS devices. For example, the thermal properties of polymers might mean that they are especially sensitivity to the speeds and reciprocating scan frequencies of measurements. This is a serious concern because the selection of appropriate materials for such applications is very important in order to reduce not only friction and wear, but also the stiction of the parts. The immediate challenge is that there is very little reliable information about the properties of this new generation of engineering materials because of insufficient understanding and characterization of their behaviour at the microscale under a wide range of experimental conditions. With these points in mind, this thesis aims to prompt wide study of the micro-tribological properties of polymers for MEMS applications, providing preliminary new data on them while exploring in some detail possible uncertainty effects that could arise from the testing regimes of most micro-tribometers. It starts by re-commissioning and characterizing a unique, wide-bandwidth prototype micro-tribometer developed at Warwick, establishing good operating procedures by comparing measurements on materials widely discussed in the literature. New data has been collected on an acrylate resin typically used for micro-stereo-lithography, PTFE and oxide-coated silicon. It suggests that deviations from Amonton’s law in the ten millinewton range might be less severe than previously reported. Observing that the skill and time required for such testing makes it unattractive for a production control environment, the thesis then explores, via contact modelling, whether there is a useful correlation between Berkovich tip nano-hardness and the micro-friction of the polymeric samples: several plausible modelling assumptions are shown to lead to inconsistencies. Final discussions and recommendations consider how to move on from these experimental scoping studies to acquire detailed evaluations of the properties of the best candidates under typical usage conditions prior to designers of potential products taking these materials and processes at all seriously.
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Micklos, Brian. "Wear mapping and tribological investigation of liquidmetal bulk metallic glass." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000953.
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Dearn, Karl David. "An investigation into tribological and performance related aspects polymeric gearing." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532276.
Повний текст джерелаАнотація:
The benefits of using polymer and polymer composite gears are numerous and it is these in part that is fuelling the resurgent commercial interest in them for metal replacement applications, thought to be in the region of £160M per annum. This interest is further driven by the increasingly important need for considerate energy consumption and the drive for greater product efficiency. As the science and technology associated with polymeric gearing develops, so too do the complexities and demands of the application. Although traditionally employed in low load and speed applications and motion control, such advancements are pushing the limits of high performance polymer applications to unprecedented levels where hitherto high temperature and corrosive environments would have excluded them. Thus, the complex kinematics of gearing and the extreme environments in which polymer gears operate make such applications ideal candidates for material manufacturers to demonstrate the superiority of their proprietary polymers. Despite this resurgent interest, polymer gears have received only a fraction of the attention received by their metal counterparts. As a result, those choosing to specify polymers in demanding applications are faced with a lack of reliable design and testing data, with current standards and guidelines based on metallic dogma. Given the fundamental differences between the two materials, this has been proved to be inadequate. This thesis aimed to address a variety of performance aspects of polymeric gears, particularly focusing on temperature and tribological related effects. At its foundation was the previous research conducted by the Power Transmission Laboratory, at the University of Birmingham. Five research areas were covered, they were: - The analysis and estimation of bulk temperatures in polymer spur gears - Contact analysis of polymeric gears - Acoustic emissions and transmission error analysis: - External lubrication analysis with respect to measured efficiencies and surface damage: -A design and rating algorithm for polymeric gears: The research utilised empirical, numerical and analytical techniques to improve the understanding of the behaviour of polymeric gears, such that their performance and reliability could be improved. In addition to this, recommendations were given for future research directions.
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Bhuyan, Satyam Kumar. "Investigation of tribological properties of biobased polymers and polymeric composites." [Ames, Iowa : Iowa State University], 2008.
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10
McCann, Laura. "Tribological investigation of articular cartilage substitution in the medial compartmental knee." Thesis, University of Leeds, 2009. http://etheses.whiterose.ac.uk/12736/.
Повний текст джерелаАнотація:
In the development of any cartilage substitution device, an understanding of the tribological response of the natural joint, as well as the treated joint is of upmost importance. Many previous studies have investigated the tribology of potential cartilage substitution therapies, using small scale pin on plate experiments. The aim of the current study was to develop an anatomical and physiological simulation of the medial compartmental bovine knee joint and to use this simulation to investigate a number of cartilage substitution therapies for damaged or diseased knee joints. A pendulum friction simulator was used to apply physiological loading and motion to medial compartmental knees. The wear of the cartilage was characterised following the experiments using three different techniques: surface topography analysis, volumetric wear quantification using µMRI scans and histological assessment. Three main interventions were investigated using this novel anatomical simulation - the tribological response of meniscectomy, the effect of conformity of tibial hemiarthroplasty designs, and finally, a number of potential cartilage substitution materials were investigated as osteochondral repair devices in the femoral condyle. In the first two studies, the removal of the meniscus and a decrease of tibial hemiarthroplasty conformity, resulted in an elevation of the coefficient of friction, contact stress, friction shear stress and subsequently the wear and degradation of cartilage. In the defect repair study, biphasic defect repair materials (hydrogels) had a superior tribological performance to non-compliant single phase materials (stainless steel). Across the three studies, the use of non-biphasic materials and/or the loss of joint congruity resulted in a more rapid decrease of cartilage interstitial fluid pressurisation and biphasic fluid load support, resulting in increased cartilage solid-solid contact and increased wear. This tribological simulation can be used to investigate many potential knee joint intervention, from uni- or hemi-arthroplasty, cartilage defect repair, meniscus substitutes or tissue engineered substitutes. This simulation can be used to further our understanding of the tribological characteristics of more satisfactory and conservative therapies for damaged and diseased synovial joints.
11
Sgarabotto, Francesco. "Investigation of tribological properties of coated high strength steels in hot stamping." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423549.
Повний текст джерелаАнотація:
The demand for weight reduction in vehicles has increased significantly over the last ten years, since the new regulations for CO2 emissions control were introduced. Furthermore, the enhanced safety requirements have promoted the development of new materials with high strength-to-weight ratio such as the high strength steel (HSS) formed at high temperatures. By using HSS hot stamped several improvements have been made – if compared with cold forming process – such as the forming forces reduction, the achievement of more complex features, the springback phenomena reduction and the component mechanical properties increase. Therefore, it has been possible to significantly reduce automobiles weight, maintaining the structural strength and safety requirements.
The process that used to form the boron steel grade 22MnB5 HSS is the hot stamping, which consists in heating a metal sheet up to austenitization temperature and then a simultaneous forming and quenching phase in closed dies to obtain martensite microstructure on the final components. Thus, ultimate tensile strength passes from 600MPa to 1500MPa.
Nevertheless hot stamping involves also some critical aspects, such as the severe tribological conditions dealing with the elevated temperature of die-blank sliding surfaces. Problems such as oxidation, material transfer, surfaces damage, wear and high friction influence the workpieces surface quality, dies durability and overall process.
A review of the literature has shown that friction behaviour of uncoated and Al-Si coated HSS has been studied by using mainly strip drawing simulative testing apparatus. The influence of different process parameters on friction coefficient – such as temperature and contact pressure – have been investigated, but results are still incomplete or not comparable.
Instead, the studies of wear mechanisms characterizing hot forming dies have revealed to be almost unexplored in several aspects. The reported studies have been focusing on conventional wear testing configurations, which are suitable to achieve fundamental knowledge on wear evolution and mechanisms, but fail in replicating the thermal and mechanical conditions to which the forming dies are subject during the industrial process. In fact, they usually do not apply any thermal cycle to the material acting as the tool, carrying out the tests at constant temperature. Otherwise, the wear phenomena has been studied through costly and time- consuming industrial trials, without any control on process parameters.
Therefore, the main target of this PhD thesis is devoted to the development of innovative approaches, based on the design of both experimental apparatus and procedures, to accurately describe and investigate tribological phenomena of sliding surfaces during hot stamping process of coated high strength steel.
To this aim, a novel simulative testing apparatus was designed to evaluate the influence of different process parameters on the friction coefficient during the hot forming process. Furthermore, a new approach of wear test based on pin-on-disc was implemented in order to:
• evaluate the main mechanisms responsible of tools wear during industrial press hardening process;
• apply controlled thermo-mechanical stress on pin materials during the test.
In order to prove the proposed procedures, diffusion and friction tests were performed in hot stamping conditions by using Al-Si and Zn hot-dip galvanized 22MnB5 high strength steel sheet. Results showed the reliability of experimental apparatus and the influence of process parameters on friction coefficients and diffusion phenomena on the coating. Furthermore Zn coating revealed a lower friction coefficient than the Al-Si one.
The new approach to wear test in hot stamping condition was proved in terms of replication of thermo-mechanical stress applicable on pin surfaces. Afterwards, three different types of die materials were tested. By using specific surface investigation tools, it was possible to analyze the main wear mechanisms, allowing a better understanding of the fundamentals of friction and wear phenomena characterizing hot stamping process of coated high strength steels. Finally the best performing material in terms of wear resistance was identified.Negli ultimi anni l’esigenza di ridurre il peso dei veicoli è notevolmente aumentata in seguito all’entrata in vigore di nuove regole per il controllo delle emissioni di CO2; inoltre, le continue richieste di miglioramento della sicurezza dei passeggeri hanno promosso lo sviluppo di nuovi materiali con elevato rapporto peso-resistenza, come gli acciai alto resistenziali formati ad alte temperature. Grazie all’utilizzo di questi materiali stampati a caldo sono stati possibili notevoli miglioramenti - anche rispetto ai processi di formatura a freddo - come la riduzione delle forze di formatura, la possibilità di ottenere geometrie più complesse, la riduzione dei fenomeni di ritorno elastico e il miglioramento delle proprietà meccaniche finali del componente. Questo ha portato ad una significativa riduzione del peso delle autovetture, pur mantenendo inalterate la resistenza della struttura e i requisiti di sicurezza imposti. Il processo usato per formare gli acciai alto resistenziali a base di boro 22MnB5 è lo stampaggio a caldo, il quale prevede il riscaldamento di un foglio di lamiera al di sopra della temperatura di austenitizzazione e le successive operazioni di formatura e tempra all’interno di stampi chiusi che avvengono simultaneamente. L’obiettivo è quello di ottenere una microstruttura martensitica nel componente finale, che consente di aumentare il carico di rottura finale da 600MPa fino a 1500MPa. Tuttavia, il processo di stampaggio a caldo presenta una serie di aspetti molto critici, quali per esempio le condizioni tribologiche connesse alle elevate temperature tra lamiera e superficie dello stampo. Problematiche come l’ossidazione, il trasferimento di materiale, il danneggiamento delle superfici, l’usura e l’alto attrito influenzano la qualità superficiale del componente, la durabilità degli stampi e l’interno processo. Uno sguardo alla letteratura rivela che lo studio dei fenomeni di attrito di acciai alto resistenziali rivestiti e non rivestiti sono valutati utilizzando principalmente l’apparato sperimentale “strip drawing”. L’influenza dei differenti parametri di processi sul coefficienti di attrito – quali temperatura e pressione normale – è stata individuata, ma i risultati non sono completi e poco comparabili tra loro. Lo studio dei fenomeni di usura che caratterizzano gli stampi usati nello stampaggio a caldo si è invece rivelato essere un campo per numerosi aspetti ancora inesplorato. I principali studi presenti in letteratura hanno focalizzato l’attenzione su test di usura convenzionali, molto utili per ottenere conoscenze sui fondamenti dell’evoluzione dell’usura, ma incapaci di riprodurre le stesse condizioni meccaniche e termiche a cui sono realmente sottoposti gli stampi durante il processo industriale. Infatti, nel corso di questi test non vengono solitamente applicati cicli termici al materiale, mantenendo la temperatura costante. In alternativa, lo studio dei fenomeni di usura viene eseguito con costose e lunghe prove industriali, che non consentono però di controllare separatamente alcun parametro di processo. L’obbiettivo di questa tesi di dottorato è dunque rivolto principalmente allo sviluppo di approcci innovativi, basati sulla progettazione sia di apparati sperimentali che di procedure, per descrivere e studiare accuratamente i fenomeni tribologici sulle superfici di scorrimento durante i processi di stampaggio a caldo di acciai alto resistenziali rivestiti. Per raggiungere questo scopo, è stata progettata una nuova macchina di prova simulativa che consente di valutare l’influenza dei differenti parametri di processo sul coefficiente di attrito durante lo stampaggio a caldo. Inoltre, è stato implementato un nuovo approccio basato sul pin-on-disc test, al fine di: • valutare i principali meccanismi responsabili dell’usura degli stampi durante lo stampaggio a caldo; • applicare stress meccanici e termici controllati sul materiale del pin durante la prova. Al fine di validare le procedure proposte sono stati eseguiti test di diffusione e di attrito in condizioni di stampaggio a caldo utilizzando lamiere alto resistenziali rivestite con Al-Si e Zn (applicati con processi di deposizione galvanica a caldo). I risultati ottenuti hanno dimostrato l’efficacia del nuovo apparato sperimentale e l’influenza dei parametri di processo sui coefficienti di attrito e sui fenomeni diffusivi nel rivestimento. Inoltre è emerso che il rivestimento a base di Zn permette l’ottenimento di coefficienti di attrito inferiori rispetto a quello a base di Al-Si. Il nuovo approccio per test di usura in condizioni di stampaggio a caldo è stato validato in termini di replicazione degli stress termo-meccanici applicati sulla superficie del pin e, successivamente, sono stati testati anche tre differenti materiali per stampi. Utilizzando specifici mezzi di investigazione delle superficie, è stato possibile analizzare i principali meccanismi di usura, permettendo una migliore comprensione di principi che stanno alla base dei fenomeni di attrito e usura nello stampaggio a caldo di acciai alto resistenziali rivestiti. Infine è stato individuato il materiale più performante in termini di resistenza all’usura.
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Johnsson, Elin. "Investigation of tribological mechanisms of a boron additive in lubricants and fuel enhancer." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-258234.
Повний текст джерелаАнотація:
The effect of using a boric acid based additive in lubricants and fuel enhancers was investigated in this study. Experiments were performed in a reciprocating and a continuous sliding ball-on-disk test equipment. Different oil types and temperatures were used. The aim of the experiments was to provide information about how these boron containing lubricants work in terms of chemistry and tribology. The surfaces after tribological contact were analyzed with Light Optical Microscopy (LOM), Vertical Scanning Interferometry (VSI), Scanning Electron Spectroscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). The boric acid based additive and the temperature used affected both the friction and wear. A higher oil temperature resulted in wider wear tracks. Oil with boron additive seemed to lower the friction coefficient at temperatures above 50 °C, compared to the same oil without boric acid; the reference oil. The tests also indicated that friction coefficients as low as 0.05 can be achieved by using a boron additive layer on the disk surface together with PAO-oil. Tribofilms containing Zn, P, S, Mg and O were formed in the wear tracks at high temperatures for both the reference oil and oil with boron additive. Oxidized regions were found in the tracks created from tests at 25 °C. Tests with oil containing boron additive resulted in lower Zn concentrations in the tracks, which is an indication that the boric acid based additive hinders the formation of these Zn rich tribofilms. To summarize, both oils and fuel enhancers with boric acid can obtain lower friction coefficients compared to those without this additive. The role of boric acid in the tests performed, both regarding the tribology and chemistry, is not yet fully understood and more chemical investigations are needed.
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Bahari, Adli. "Investigation into tribological performance of vegetable oils as biolubricants at severe contact conditions." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19524/.
Повний текст джерелаАнотація:
The concern about the pollution created by the use of mineral oil based lubricants and the depletion stock of petroleum has inspired research on alternative lubricants known as biolubricants. The tribological performance of vegetable oils (palm oil and soybean oil) as biolubricants and their blends with mineral oil and anti-wear additives was evaluated in order to assess their potential use in automotive engines. The tests were performed using a reciprocating ball-on-flat test-rig at severe contact conditions with grey cast iron specimens. The performance was compared with a commercial mineral engine oil for benchmarking purposes. At severe contact conditions, the friction and wear results of vegetable oil lubricants were found to be greatly influenced by the wide hardness range of the grey cast iron specimens. The measurement of hardness on the intended wear scar region prior to testing was used in order to provide more robust tribological data. In a pure oil state, the palm oil performance was found to be competitive in friction coefficient with mineral engine oil. However, the mineral oil is far superior in wear protection over vegetable oils due to the additive package it contains its superior oxidative stability. For a vegetable oil-mineral oil blend in equal ratio, the reduction of friction and wear was not significant. However, the addition of 2% zinc dialkyl dithiophosphate in vegetable oils gave significant improvement on the friction and wear. The friction coefficient of palm oil with this additive was very close to the commercial mineral engine oil. The zinc dialkyl dithiophospate in vegetable oil was found to perform three functions; as an anti-wear agent, anti-oxidant and friction modifier. The blend of vegetable oils with boron nitride, however, did not give better results. This could be mainly due to the selection of particles size which was not suitable with the surface roughness. When putting all the results together, the downside of pure vegetable oils is found to be greater in terms of wear resistance and oxidative stability compared to friction. This effect was prominent when they were blended with mineral oils where their tribological performance dominated. However, with the commercial anti-wear additive, specifically the zinc dialkyl dithiophosphate, the vegetable oils showed positive signs as a potential candidate to be used as an alternative lubricant in automotive engine systems even though there is still much room for improvement.
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Rao, M. "An investigation of the tribological behaviour of polymeric materials in rolling-sliding contacts." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680647.
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Towsyfyan, Hossein. "Investigation of the nonlinear tribological behaviour of mechanical seals for online condition monitoring." Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34340/.
Повний текст джерелаАнотація:
Mechanical seals have increasingly been used for sealing rotating shafts in centrifugal pumps, propeller shafts in ships and submarines, compressors, liquid propellant rocket motors in aerospace industry, pumps, turbines, mixers and many other rotating machines during last two decades. Abnormal operating conditions in the mechanical seals will degrade machine performance, increase operating cost and may cause unexpected sudden failures which are dangerous in both engineering and safety terms. Hence it is necessary to investigate the tribological behaviour of mechanical seals operating based on nonlinear coupling between fluid and surface dynamics, in order to develop more advanced diagnostic technologies to improve the reliability of such machines operating with mechanical seals. Different condition monitoring techniques have been studied to evaluate the lubrication state and severity of contact between the mating faces in mechanical seals. However, some of them are not cost effective others are not practical in industrial applications. Acoustic emission (AE) has been proved to be a sensitive indicator of lubrication conditions and changes in the lubricant properties, however the application of technique for identification of lubrication regimes in mechanical seals has not been reported yet. Moreover, previous studies give relatively little information to acoustic emission condition monitoring of mechanical seals, nor has comprehensive fault detection been implemented for a particular case. In addition, a review on previous works reveals the lack of comprehensive mathematical models to explain the relationship between AE energy and tribological characteristics of the mating faces under healthy and faulty conditions. In this research, the tribological behaviour of mechanical seals is investigated using acoustic emission measurements to pave a way for fault detection at early stage. Three common seal failures i.e. dry running, spring fault, and defective seal are studied in this thesis. The main objective is to extract AE features that can explain the tribological behaviour of mechanical seals under both healthy and faulty conditions. To achieve this, a purpose-built test rig was employed for collecting AE signals from the mechanical seals. Then, the collected data was processed using time domain, frequency domain and time frequency domain analysis methods which are of the most common techniques used for monitoring in AE applications. Based on results the main frequency band that can present the tribological behaviour of mechanical seals was detected. Also it has been proved that AE features in time domain and frequency domain can be effectively applied to indicate the lubrication condition of mechanical seals as well as early fault detection. Moreover, mathematical models were developed to establish a relationship between AE root mean square (RMS) value of AE signals and working parameters of seals (rotational speed, load and number of asperities in contact) under different lubrication regimes. A good agreement was achieved between measured and predicted signals that gives a good evidence of the effectiveness of proposed models. Especially in case of leakage that is one of the main situations indicating the seal failure, a significant difference was observed between the predicted signal for healthy case and the measured signal under faulty conditions. Therefore, it can be deduced that the AE measurement system and signal processing developed in this work has a promising potential to be used to diagnose and monitor the mechanical seals online. Finally, the conclusions and achievements are given based on the entirety of this research work, and online monitoring incorporating with AE features and mathematical models developed in this thesis are suggested as the main works for further research.
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Stone, D'Arcy S. "Tribological investigation of nanocomposite thin films of transitional metal nitrides with silver inclusions." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/768.
Повний текст джерелаАнотація:
In this tribological study, a temperature dependent inquiry of the changes in chemistry and crystal structure of two selected double metal oxides is undertaken. It is known that chameleon coatings of Mo2N/Ag/MoS2 produce a friction coefficient of 0.1 from wear testing at 600 °C for 300,000 cycles. The low friction is attributed to the formation of silver molybdates layers, a lubricious double-metal oxide, in the coating. Double-metal oxides consisting of a group 6 transitional metal and silver (silver molybdate (Ag2Mo2O7) and silver tungstate (Ag2WO4)) were used for this investigation. Thin films and powders were investigated using high temperature x-ray diffraction, high-temperature Raman spectroscopy and differential scanning calorimetry in tandem with sliding tests from 25 to 600 °C. Our results were compared to external ab-initio molecular dynamic simulations performed elsewhere to qualify experimental results. The layered atomic structure of silver molybdate facilitates sliding, resulting in a low coefficient of friction (<0.2) from 300-500 °C. Unlike Ag2Mo2O7, however, Ag2WO4 does not possess a layered atomic structure and produced coefficients of friction (>0.4) in all temperature ranges between room temperature and 500 °C. Applying the knowledge gained from prior studies of the intrinsic properties of double metal oxides of group 6, chameleon coatings consisting of group 5 transitional metal nitrides (vanadium nitride, niobium nitride, and tantalum nitride) with silver inclusions were created using unbalanced magnetron sputtering to investigate their potential application as adaptive, friction reducing coatings. The coatings were tribotested against a Si3N4 counterface in the 22 to 1000 °C temperature range. In-situ Raman Spectroscopy measurements were taken during heating and wear testing at 700 °C to identify the evolution of phases in the coatings' surfaces and in the wear track. The chemical and structural properties of the coatings were also characterized before and after wear testing using x-ray diffraction. At higher temperatures, oxygen, silver and the transition metals react on the surface to form potentially lubricious double oxide phases (silver vanadate, silver niobate and silver tantalate). All coatings performed similarly up to 750 °C. The VN/Ag coating, however, had a lower coefficient of friction at 750 °C comparatively to TaN/Ag and NbN/Ag, likely due to its reported lower melting temperature (450 °C) and its layered crystal structure.
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Forsey, Richard. "Development of cartilage damage models for a tribological investigation of therapeutic lubricants in osteoarthritis." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411310.
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Singh, Harpal. "An Investigation of Material Properties and Tribological Performance of Magnetron Sputtered Thin Film Coatings." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1449850005.
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Cheung, Man Kuen. "Investigating the tribological performance of different polymer and polymer nanocomposites using nanoscratch and wear techniques /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-ap-b19887772a.pdf.
Повний текст джерелаАнотація:
Thesis (M.Phil.)--City University of Hong Kong, 2005."Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references (leaves 82-95)
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Salama, M. R. El-M. "Investigation into the effect of fibre size on the tribological behaviour of semi-metallic brake material." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384145.
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Wei, Nasha. "The investigation into the condition monitoring of tribological behaviour between piston ring and cylinder liner using acoustic emissions." Thesis, University of Huddersfield, 2018. http://eprints.hud.ac.uk/id/eprint/34761/.
Повний текст джерелаАнотація:
To improve engine operational performance and reliability, this study focuses on the investigation into the behaviour of tribological conjunction between the ring - liner based on a comprehensive analysis of non-intrusive acoustic emission (AE) measurement. Particularly, the study will provide more knowledge of using AE for online monitoring and diagnosing the performances of the conjunction. To fulfil this study, it integrates analytical predictions of the theoretical modelling for the AE generation mechanism with extensive experimental evaluations. Moreover, effective signal processing techniques are implemented with a combination of the model based AE predictions to extract the weak and nonstationary AE contents that correlate more with the tribological behaviour. Based on conventional tribological models, tribological AE is modelled to be due to two main dynamic effects: asperity-asperity collision (AAC) and fluid-asperity interaction (FAI), which allows measured AE signals from the tribological conjunction to be explained under different scenarios, especially under abnormal behaviours. FAI induced AE is more correlated with lubricants and velocity. It presents mainly in the middle of engine strokes but is much weaker and severely interfered with AEs from not only valve landings, combustion and fuel injection shocks but also the effect of considerable AACs due to direct contacts and solid particles in oils. To extract weak AEs for accurately diagnosing the tribological behaviours, wavelet transform analysis is applied to AE signals with three novel schemes: 1) hard threshold based wavelet coefficients selection in which the threshold value and wavelet analysis parameters are determined using a modified velocity of piston motion which has high dependence on the AE characteristics predicted by the two models; 2) Adaptive threshold wavelet coefficients selection in which the threshold is gradually updated to minimise the distance between the AE envelopes and the predicted dependence; and 3) wavelet packet transform (WPT) analysis is carried out by an optimised Daubechies wavelet through a novel approach based on minimising the time and frequency overlaps in WPT spectrum. Based on these optimal analyses, the local envelope amplitude (LEA) and the average residual wavelet coefficient (ARWC) are developed from AE signals as novel indicators to reflect the tribological behaviours. Both the hard threshold based LEA and wavelet packet transform LEA values allow two different new lubricants to be diagnosed in accordance with model predictions whereas they produce less consistent results in differentiating the used oil under several operating conditions. Nevertheless, ARWC can separate the used oil successfully in that it can highlight the AAC effects of particle collisions in used oils. Similarly, LEA shows little impacts of two alternative fuels on the tribological behaviours. However, ARWC shows significantly higher amplitudes in several operating conditions when more particles can be produced due to unstable and incomplete combustions of both the biodiesel and FT diesel, compared with pure diesel, indicating they can cause light wear.
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Li, Guoxing. "Investigation into the dynamic responses and tribological characteristics of cylinder liners in a IC engine with alternative fuels." Thesis, University of Huddersfield, 2016. http://eprints.hud.ac.uk/id/eprint/30287/.
Повний текст джерелаАнотація:
Promoted by the realisation of dwindling fossil fuel supplies and their adverse environmental impacts, there more and more types of alternative fuels to fossil diesel have been used and investigated in compression ignition engines. However, the majority of researches on alternative fuels mainly focus on their power performance, efficiency and emission performance, without fully investigating the potential effects on the vibro-acoustic emissions and tribological characteristics of engines caused by their significant differences in physical and chemical properties. Consequently, the impacts of long-term use of alternative fuels on structural failure, lubrication degradation, friction aggravation, overall service life spans and associated maintenance activities of internal combustion (IC) engines have not yet been fully understood. To reduce this gap this thesis focuses on the investigation into the vibration responses of cylinder liners in a diesel engine to accurately characterises the tribological behaviour between the piston rings and cylinders which is one of the most decisive sub-processes that determine engine performance and yet is correlated with the combustion of different fuels. In particular, the investigation was carried out by coupling the hydrodynamic lubrication model with structural vibration effects through a series of extensive numerical simulations and systematic experimental evaluations in order to establish a vibration based technique to monitoring tribological behaviour and thereby accurately assess the influence. Based on the dynamic coupling mechanisms between the combustion characteristics of alternative fuels and the tribological behaviours of cylinder liners, the most significant influences from the fuel burning on tribological behaviour of cylinder liners concerned in this study is a direct and physical approach such as the effect of liner vibrations on cylinder friction process, even though an indirect and chemical but very slow approach such as the deterioration of oil properties by combustion products can happen. To characterise the direct influence a finite element dynamic model was developed and validated for predicting the dynamic responses of cylinder liners to respective excitation sources including the highly nonlinear combustion pressure shocks and subsequent piston slap impacts. The realistic consideration of both the characteristics of structural modes up to 15kHz and nonlinearities of elastic assembly constraints allows obtaining accurate prediction that the combustion shocks cause vibrations in a frequency range around 10kHz with an amplitude order of 0.01μm, whereas the piston slaps in frequency range from 1k to 5kHz with an amplitude order 0.2μm, which gives a clear and quantitative indication of the nonlinear phenomena of liner vibration due to combusting alternative fuels and varying lubrication conditions. In addition, a decomposition analysis of piston side-thrust forces provides more insight of the localized response characteristics corresponding to coupling interactions of combustion force with inertia force of piston assembly. To further investigate the potential influences of structural deformations to tribological behaviours of cylinder assemblies, a new dynamic deformation based lubrication model was developed based on an employment of improved shearing factors in which the effect of inevitable liner vibrations is included to obtain a more realistic lubricating film formation, distribution and tribological behaviours. The simulation studies show that this advancement in modelling oil films predicts that the biodiesel with more intense vibration emissions is able to reduce the friction loss between pistons and liners, whereas the methanol-diesel blend with weakened liner dynamic response may exacerbate the friction loss of IC engines. This finding confirms further that the vibration responses allow a straightforward and in-depth indication of the effect generated by using different fuels. In addition, a further experimental investigation was carried out based on a motoring engine test, in which high frequency sinusoidal vibrations at 25 kHz, 30 kHz and 40 kHz are added to the external surface of the linear. The observable changes in motoring torque verify that proper external vibrations can affect the tribological behaviours between the pistons and liners, including both asperity friction and viscous friction, and resulting in the friction reduction of IC engines. Particularly the 40 kHz vibration at the maximal driving power of the test device can achieve a reduction of 1.79% in the motoring torque. This has demonstrated more on the effectiveness of this vibration based diagnostic method in assessing the influences of alternative fuels upon tribological behaviours of piston ring and cylinder liners. Finally, further researches on the subjects is also proposed in order to complete the vibration based diagnostics in achieving more accurate assessment of engine lubrication conditions and effective friction reduction.
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Mahmoudi, Behzad. "Investigation the Effect of Tribological Coatings: WC/a-C:H and Black Oxide on Micropitting Behavior of SAE52100 Bearing Steel." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444838738.
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Eichhorn, Sven, and Christine Schubert. "Component analysis of a fully implemented sectional WPC-beam with tribologic value as sliding rail utilized in a overhead conveyor system." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-153125.
Повний текст джерелаАнотація:
The sectional beam is the essential detail of an overhead conveyor. The construction element is stressed by time-varying mechanical and tribological loads. Here, we discuss the influence of the manufacturing process on the mechanical properties and the serviceability of the extruded profile in a selected application. The development of existing formulas and processing parameters are shown with the objective to expand the material application from WPC-decking to use in mechanical engineeringDas Tragprofil ist das zentrale Element in einem Hängefördersystem. Das Bauteil wird durch zeitlich veränderliche mechanische und tribologische Lasten beansprucht. Nachfolgend wird der Einfluss des Herstellungsprozesses auf die mechanischen Eigenschaften und die Gebrauchsfähigkeit eines extrudierten Trag- und Gleitprofils aus WPC im gewählten Anwendungsfall vorgestellt. Die notwendige Weiterentwicklung bestehender Rezepturen und Verarbeitungsverfahren wird aufgezeigt, um den Anwendungsbereich des Werkstoffes WPC vom Bereich Terassendielen auf den Maschinenbau zu erweitern
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Yupanqui, Aliaga Edson Igor. "Implementation of a triboelectrical workstation for the investigation of the influence of electrical current on the tribological properties of thin films." Master's thesis, Pontificia Universidad Católica del Perú, 2016. http://tesis.pucp.edu.pe/repositorio/handle/123456789/6986.
Повний текст джерелаАнотація:
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.Tesis
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Karniychuk, Maksim. "Combination of Lateral and Normal Forces for Investigation of Mechanical Properties and Tribological Behaviour of Bulk and Coated Materials on the Micro-Scale." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601120.
Повний текст джерелаАнотація:
In the last half of the XX century and the first years of the XXI century a large amount of methods for the determination of mechanical and tribological properties of materials on the micro- and nano-scale were developed. However, some problems and disadvantages are kept up to now. The combined application of normal and lateral forces allows to extend the possibilities of conventional contact mechanical approaches for investigations of mechanical and tribological behaviour of bulk and coated materials. Due to the unique construction of the Lateral Force Unit (LFU) the lateral force can be applied to the sample during normal indentation by the commercial nanoindenter UMIS 2000. Thus, the presented thesis reports the detailed study of the LFU capabilities for the determination of mechanical properties and tribological behavior on the micro-scale. At first it was found that the most appropriate standard position for the correct combined application of normal and lateral forces is the LFU inclination by 3.3° with respect to the UMIS stage. This standard position allows to minimize the influence of different factors on the measuring process. It was shown that the shape of normal displacement-time curves is the most convenient after the thermal drift correction for the simplification of the determination of such parameters as the maximal normal displacement and the residual normal deformation obtained by lateral force application. It was found that the crack formation can be detected as the observation of sudden change of lateral displacement in lateral force-displacement curve together with normal displacement in normal displacement-time curve. These investigations were performed for single-crystal sapphire. For the first time the crack in single-crystal sapphire was detected by the contact mechanical method in situ. The critical tensile stress for the crack formation in single-crystal sapphire was determined as 9.68+-0.22 GPa. It was established that the onset of plastic deformation can be detected by the observation of shape change of lateral force-displacement curve together with the appearance of residual normal deformation in normal displacement-time curve. These investigations were done for bulk BK7 glass and silicon dioxide film with thickness of 951 nm on silicon substrate. The yield strength for the silicon dioxide film was evaluated as 6.83+-0.02 GPa. It was found that the static friction of materials couples can be evaluated by the analysis of lateral force-displacement curves with the error of 5-10 %. The static friction coefficients for fused silica, BK7 glass, single-crystal sapphire as well as SiO2, DLC and CrN0.08 coatings were determined against diamond, tungsten carbide and sapphire spherical indenter with different radii. The effect of normal load on static friction for fused silica and BK7 glass against 10.5 µm diamond spherical indenter was also studied. It was found that the onset of plastic deformation leads to a significant change of static frictionIn der zweiten Hälfte des 20. Jahrhunderts und während den ersten Jahren des 21. Jahrhunderts wurden zahlreiche Methoden zur Untersuchung mechanischer und tribologischer Materialeigenschaften auf der Mikro- und Nanometerskala entwickelt. Trotz der Fortschritte auf diesem Gebiet blieben vielfältige Fragestellungen unbeantwortet oder waren mit den vorhandenen experimentellen Untersuchungsmethoden nicht zugänglich. Mit der kombinierten Belastung aus Lateral- und Normalkräften wurden die etablierten Messverfahren um einen viel versprechenden Ansatz zur Charakterisierung mechanischer sowie tribologischer Eigenschaften erweitert, der sowohl für Massiv- als auch Schichtmaterialien anwendbar ist. Die einzigartige Konstruktion einer Lateralkrafteinheit bietet als separates Bauteil die Möglichkeit während eines Standardeindringversuches mittels des kommerziellen Nanoindenters UMIS 2000 bei normaler Last, eine laterale Belastung zu überlagern. Die vorliegende Arbeit zeigt eine detaillierte Studie der Einsatzmöglichkeiten der Lateralkrafteinheit hinsichtlich der Charakterisierung mechanischer Eigenschaften und tribologischen Materialverhaltens auf der Mikrometerskala. Zunächst wurde herausgefunden, dass eine Verkippung der Lateralkrafteinheit von 3,3° gegenüber dem UMIS-Rahmen notwendig ist, um eine hochgenaue und definierte Belastung aus lateraler und normaler Kraft auf die Probe auszuüben. Mit dieser durchgeführten Korrektur der Ausrichtung gelang es weitere auf den Messprozess einwirkende Effekte zu minimieren. Nach der Korrektur der thermischen Drift scheinen die gemessenen Normalverschiebungs-Zeit-Kurven für die Bestimmung von mechanischen Parametern wie maximaler Verschiebung oder bleibender Eindrucktiefe bei lateraler Belastung geeignet zu sein. Als ein weiteres Ergebnis gelang es, durch die kombinierte Belastung der Kraftkomponenten Bruchversagen nachzuweisen. Das Materialversagen wurde durch eine abrupte Änderung der lateralen Verschiebung im Last-Verschiebungs-Diagramm angezeigt. Mit dieser Methode wurde erstmalig in-situ das Bruchversagen am Beispiel des einkristallinen Saphirs detektiert. Die kritische Zugspannung, die zur Bruchbildung bei Saphir führte, war 9,68+-0,22 GPa. Die Analyse der Kurvenform der Kraft-Verschiebungs-Kurven für die Lateralbelastung im Zusammenhang mit dem Auftreten von bleibender Deformation in den zugehörigen Verschiebungs-Zeit-Kurven der normalen Belastung liefert den Beginn der plastischen Deformation. Massive BK7-Glasproben sowie SiO2-Schichten wurden untersucht. Für die Fließspannung der SiO2-Schicht wurde ein Wert von 6,83+-0,02 GPa ermittelt. Der Haftreibungskoeffizient für verschiedene Materialpaarungen wurde aus den Last-Verschiebungs-Kurven mit einer Genauigkeit von 5-10 % berechnet. Zu den untersuchten Materialien gehörten Quarz, einkristallines Saphir, BK7-Glas sowie SiO2-, DLC- und CrN0.08-Schichten, die mit Diamant, Wolframkarbid und Saphir-Indentern gepaart wurden. Zusätzlich wurde der Einfluss der Normallast auf den Haftreibungskoeffizienten für Quarz und BK7-Glas gegen Diamant studiert. Es zeigte sich, dass der Beginn der plastischen Deformation zu signifikanten Änderungen der Haftreibung führt
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Albo, Zieme Louise, and Pontus Bergstedt. "A pre-study for functional coatings evaluated on light metals to be applied on a new HPDC Mg-alloy : Investigating tribological and thermophysical properties, as-cast and coated." Thesis, Jönköping University, JTH, Industriell produktutveckling, produktion och design, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-53096.
Повний текст джерелаАнотація:
Magnesium with two-thirds of the density compared to aluminium and one-quarter of steel, intrigues product developers and material scientists due to the light metal’s excellent combination of strength to weight ratio as well as their capability of being produced as a High Pressure Die Cast component compared to other ferrous or light metal alloys. However, a magnesium alloy inherits some concerning drawbacks, limiting the exploitation in structural applications and mechanical design such as automotive, heavy machinery and aerospace components. The need for a magnesium alloy that could withstand a sufficient amount of wear, temperature and corrosive environment, leads towards the investigation and evaluation of a suitable, functional coating as a solution to exploit the evident advantages a magnesium alloy exhibits. A substantial amount of research is required in order to reduce an existing knowledge gap that is the ongoing development in the search for a sufficient functional coating and adherence capability to the highly reactive substrate that is a magnesium alloy. This industrial master thesis is an early stage investigation to evaluate how the currently used aluminium substrate with an electrodeposited coating relate and compares to a heat-treated electroless deposited coating through tribological and thermophysical induced stresses. These properties are tested with proven industrial standard methods resulted in a comprehensive conclusion and discussion regarding the feasibility of applying the coating onto a commercial magnesium alloy closely related to the Mg-alloy developed by Husqvarna and thereby contributing to technological advances to the highly relevant topic within product development in materials engineering.
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Walkowiak, Wiesław. "Investigation of influence of the chemical composition and structure of selected hard coatings, deposited of PVD methods, on their mechanical properties : doctoral dissertation." Rozprawa doktorska, [s.n.], 2001. http://dlibra.tu.koszalin.pl/Content/1224.
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Karniychuk, Maksim B. "Combination of lateral and normal forces for investigation of mechanical properties and tribological behaviour of bulk and coated materials on the micro-scale Kombination von Lateral- und Normalkräfte für die Untersuchung von mechanischen Eigenschaften und des tribologischen Verhaltens massiver und beschichteter Materialien im Mikrometerbereich /." [S.l. : s.n.], 2006.
Знайти повний текст джерела
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SPINELLI, MICHELE. "Experimental tribological investigations of articular bearings for lower limb prosthesis." Doctoral thesis, 2009. http://hdl.handle.net/2158/590125.
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THAKUR, RANJEET KUMAR. "TRIBOLOGICAL INVESTIGATIONS OF MILD STEEL PINS OF DIFFERENT CROSS-SECTIONAL AREA WITH CAST IRON PLATE." Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/17196.
Повний текст джерелаАнотація:
Mechanical, electromechanical and biological systems are used in every engineering application and it has been noted that the substantial amount of energy is consumed in overcoming friction between the mating surfaces of these systems. Wear of parts or components results in resource wastage and unnecessary heat generation. A huge amount has been spent till date to cover for friction and wear losses. The study of tribological properties (i.e., friction, wear and lubricants) has gained significance in the recent years as an effort for the development of new material to reduce the frictional losses. Tribological study has of utmost importance for many systems which depends on wear and friction values. There could be enormous amount savings by improved tribological practices over the system.
The experimental study of tribological characteristics contains study of friction and rate of wear of tribopair for which experiment was carried in lubricated conditions at different temperatures. The high temperature Rotary Tribometer was applied for determination of coefficient of friction and rate of wear at interface of tribopair. From the results so obtained after experiment, it was found that the wear rate initially had high value of 7 x 10-6 mm3/Nm and then decreased to a stable value of 2 x 10-6 mm3/Nm. The coefficient of friction initially had value of 0.14 which then decreased to a stable value of 0.04 after having attained constant relative speed of tribopair.
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Rekha, Rattan. "Investigations on mechanical and tribological properties of carbon fabric reinforced polyetherimide composites." Thesis, 2006. http://localhost:8080/xmlui/handle/12345678/4512.
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K, Rajkumar. "Microwave processing, characterizatin and tribological investigations on copper-graphite, copper-carbon nanotube and copper-nanographite composites." Thesis, 2012. http://localhost:8080/iit/handle/2074/5314.
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Sheng-ChieHuang and 黃聖傑. "Investigation of Mechanical and Tribological Behaviorof Organic Friction Material." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/haaswf.
Повний текст джерелаАнотація:
碩士國立成功大學
材料科學及工程學系碩博士班
101
The purpose of this research is to investigate squeal and composition (metal, Friction agent and Lubricant ) on tribological properties of NAO friction material. The mechanical properties, tribological properties, and microstructure of NAO friction material are measured by mechanical tester, Rockwell hardness tester, sliding wear tester, surface roughness tester, x-ray diffraction and scanning electron microscopy. The results indicate that the NAO friction material with A show low squeal and sufficient of friction. The NAO friction material with Friction agent dust show high hardness, compression and less squeal appearance. The optimal containing amount of Friction agent is X2 vol% in this research. In addition, the NAO friction materials with graphite powder show lower friction coefficient and protect counter pad. Consequently, base on high toughness, high hardness, high compressive strength, coefficient of friction, and brake noise, the L2 specimen is the best NAO friction material.
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Choudhary, Tika Ram. "Tribological investigation of heavy duty polymer based thrust pads." Thesis, 2001. http://localhost:8080/xmlui/handle/12345678/4503.
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Chen, Jin-Duo, and 陳金多. "Investigation of Constant Speed Tribological Behavior of Carbon- Carbon Composites." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/37580391586288373484.
Повний текст джерелаАнотація:
博士國立成功大學
材料科學(工程)研究所
83
This thesis compares the basic properties and the tribological behavior under different wear conditions of six different carbon-carbon composites, including one two-dimensional PAN/ CVI- (E), one two-dimensional pitch/ resin/CVI- (A), one three- dimensional PAN/pitch- (T3D) and three two-dimensional PAN/ pitch- (TH, TM and TL) based carbon-carbon composites. The corresponding tribology mechanism is also discussed. The results demonstrate that, after wear, three different types of debris morphologies on the worn surfaces are identified. The smooth type I and type III debris film is able to lubricate, but the powdery type II debris is not. Whenever a morphological transition (type I - to -type II) occurs, transition in friction and wear also occurs. For the sliding conditions of high sliding speed and load, and low humidity generally accelerate the occurrence of transitions. On the other hand, with increasing speed and load, and decreasing humidity, the worn surface condition become more severe. The minimum weight loss is measured in the specimen sliding at the same speed as that for breaking-in. During wear test, the debris layers are deformed and fractured, the damage increases with the sliding distance. The occurrence of transition can be attributed to the adsorption of condensable vapors (or gases). The transition takes place immediately when the amount of adsorption is below a critical value. The initial type I debris is formed and is able to lubricate according to the preferred orientation and vapors adsorption theories of the basal planes. The basal planes of type II debris are aligned in random order causing lack of lubrication. All of the collected debris from type II is particulate-type. During the wear process with mild wear condition, the particulate type II debris is flatten to become lubricative type III film, and the collected debris is lamina-type.
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Cian, Hong-Jhou, and 錢竑州. "Investigation of Tribological Mechanisms on Nanoparticle Using Molecular Dynamics Simulation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/35187879970566852761.
Повний текст джерелаАнотація:
碩士國立臺灣大學
土木工程學研究所
102
Nanoparticle (NP) is a nano-scale material with diameters ranging from tens to hundreds of nanometer. Treating this nanoparticle as lubricant additives can further improve mechanical performance and durability. Hence the tribological properties of nanoparticle have gained much attention and the lubrication mechanisms of nanoparticle have been considered as an important issue. The single inorganic fullerene-like nanoparticle (IF-NP) would display rolling and sliding behavior when nanoparticle is subjected to lateral displacement under low contact stress. However, it has not been revealed that whether the rolling behavior of IF-NP is one of the significant lubrication mechanisms. Meanwhile, under contact stress, adhesion hysteresis play an important role in the rolling mechanism. However, it is not clear whether such effect influence NP rolling mechanism. The objectives of this study are twofold, first to study the friction coefficients and tribological mechanisms of a single molybdenum disulfide (MoS2) IF-NP using molecular dynamics simulation. It has been interpreted in this work that the rolling behavior is indeed a remarkable lubrication mechanism. Through these results, we can provide a guideline which will enable the design of NP with high performance of lubrication. The second objective is to address the effect of adhesion hysteresis on the onset of the rolling of nanoparticles. The results from the atomistic studies are compared with analysis from the elasticity theory. Until now, there are few appropriate molecular dynamics simulator which can describe the Mo-S covalent bond system. In the present study, a covalent bond potential describing the interaction between molybdenum and sulfur atoms has been implemented in LAMMPS. This implementation will benefit researchers to undertake the future studies in Mo-S system. It has been reported that rolling behavior could result in significant lubricant effects. From our results, the rolling behavior could reduce the friction for about 30%, which demonstrates that the rolling behavior is a significant lubricant mechanism for MoS2 nanoparticle. In addition, we observed the repeating behaviors when nanoparticle is rolling and categorized these behaviors into two rolling patterns. The adhesion hysteresis plays an important role in the rolling mechanism. We therefore extended the continuum theory to atomic scale for interpreting the influence of adhesion hysteresis within rolling behavior. Present study indicates that the adhesion hysteresis represented by a difference of energy release rates, is apparent at the onset of rolling. The peak value of difference of energy release rates occurs when nanoparticle starts to roll. This result has agreed well with the rolling friction theory proposed by Krijt. Therefore, we conclude that the critical difference of energy release rates is a material property for the onset of rolling. This property can be used to determine whether a given nanoparticle is easy to roll. From our study, the tribological mechanisms have been investigated using molecular dynamics simulation. A Mo-S system bond-order potential has been implemented in LAMMPS. We conclude that the rolling behavior is certainly an important lubricant mechanism, which has been demonstrated in present study. We also observe repeating behaviors when MoS2 nanoparticle is rolling. Moreover, how the adhesion hysteresis influences the onset of rolling of nanoparticle has been revealed as well.
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Lin, Hsin-Han, and 林信翰. "An Investigation on Tribological Properties of CrSiN Films Adherent Silicon." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/42822954460827693364.
Повний текст джерелаАнотація:
碩士國立臺灣海洋大學
機械與機電工程學系
97
The chromium nitride thin films have good corrosion resistance and mechanical properties. But the drawback is the slightly lower hardness than other hard coatings. The concept of nanocomposite thin films is employed by adding silicon to form Cr-Si-N thin films with enhanced hardness and wear resistance. In this study, the Cr-Si-N films with various Si contents were coated on silicon wafer to enhance the tribological properties and anticorrosion by a bipolar symmetry pulsed DC reactive magnetron sputtering process. The tribological properties were studied by pin-on-disk tests. The tests were conducted under the same operating condition in different environment. The corrosive characteristics were researched by potentiodynamic test and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. An atomic force microscope (AFM) was used to detect their tribocorrosion behavior in a 0.01M NaCl solution. Two loading conditions were actuated to investigate the wear corrosion. The forces were applied by controlling the potential inputs (0V and 1V) of AFM probe’s piezo actuator. As worn results, silicon content was decreased, which surface’s has a better resistance. But the results were not related with the film’s hardness and resistance to plastic deformation.
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Chen, J. G., and 陳俊吉. "Tribological performance investigation of the steels bonded with solid lubricants." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/04757061214542741220.
Повний текст джерела
40
Barik, Sanjog, and Brijesh Kumar Singh. "Experimental Investigation of Tribological Properties of Cu/Al2O3/TiO2 composites." Thesis, 2012. http://ethesis.nitrkl.ac.in/3270/1/A_final_thesis.pdf.
Повний текст джерелаАнотація:
Tribological properties play an important role in day to day life. Tribology includes study of friction, wear and lubrication. Tribology comes in picture when there is relative motion between two surfaces in contact. When there is relative motion between two surfaces in contact, there is loss of material rubbing each other. In order to minimize friction and wear, we can choose suitable lubricant. This project aims at fabricating pin on disc machine, preparing three composites made from copper, alumina and titanium dioxide by powder metallurgy process and conducting wear test for the three composites by help of pin on disc machine. By conducting the wear test, graphs are plotted between wear rate and sliding velocity. From the results obtained, effect of sliding velocity and composition of composites on wear rate of the three specimens were analysed.This investigation will help us to improve the tribological behavior of rubbing surfaces by varying their composition. The details of experimentation and analysis are given in the following context.
41
Lee, Jen-Tein, and 李仁田. "An investigation of graphite additive on the tribological behavior of greases." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/31653365672509225819.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
機械工程研究所
83
The experiment was conducted to investigate the effect of the lubricaty for lithium base grease and lithium complex base grease in various temperature and additive of graphite by way of test result, by using a reciprocating high frequency wear machine. In the same rate of graphite additive, the results indicate that the lithium base grease perform a lower friction coefficient in a higher temperature. Also,the friction coefficient decrease with increasing the rate of graphite additive in the temperature .However, there is no evident influence of friction coefficient as the additive rate is more than 5%. Futhermore, greases show lower friction coefficient in higher temperature if there is no graphite additive. For the boundary lubrication between the SKD-11 rod and SKD-11 plate, because the sliding distances of the experiment order only 1㎞. the apperance of wear is not clear, so it can't obtain the property of Wear behavior.
42
Huang, Jhih-Wei, and 黃志偉. "Investigation of Tribological Properties of Poly methy1 methacrylate/Titanium Dioxide Nano Composite." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/20677430774673480903.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
機械工程系碩士班
93
In these several years, the outstanding features of nano composite have been focused on. A developing industrial revolution is brought by the growing nano composite technologies that are efflorescent globally. According to recent research, the key technologies of nano composite application are believed to be particulates’ dispersion and diameter. In this thesis, MMA is mixed through Sol-Gel processing into the organic-inorganic hybrid nano composite PMMA-HEMA-Ti(OBu)4X%, which is produced from titanium dioxide. TiO2 and PMH are connected by chemical bonds to achieve molecular composition. It is then used to produce the bulk and thin film samples. The wear resistance and friction behavior of the bulk specimens are measured on a pin-on-disk tribometers. The effects of the composite component, loading, and sliding velocity on the wear rate and friction force have been observed. On the other hand, nano indentation and scratch tests are conducted on the thin film specimens for the purpose of comparison. The hardness, reduced modulus, scratch resistance, and surface topography in the nano scale are measured for the thin films to analyze the influences of titanium dioxide. Based on the result of bulk experiments, with increasing PV (pressure and velocity) value, the lowest wear rate was achieved for PMH with 20 wt% TBT. However, for PMH content 30wt% and 40 wt% TBT, the wear resistance is weaker than the pure PMH. In addition, the titanium dioxide does not influence the coefficient of friction. For thin film specimens, mixing inorganic into the PMH can increase the depth of scratch and therefore reduce the resistance to abrasive wear. The TGA and MDSC analyses show that the glass transition temperature of material is not affected while the decomposition temperature is increasing. In conclusion, there is no correlation regarding the results of wear and friction experiments between bulk and thin film specimens. This might due to the discrepancy of the molecular structure of material and the thermal effect during sliding contact.
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Basumatary, Kamal Kumar. "Investigation into Mechanical and Tribological Properties of Ipomoea carnea Reinforced Epoxy Composite." Thesis, 2013. http://ethesis.nitrkl.ac.in/5168/1/211ME1375.pdf.
Повний текст джерелаАнотація:
Ipomoea carnea, locally called as “Amari” is one such natural resource found abundantly in many parts of India, whose potential as fiber reinforcement in polymer composite has not been explored till date. Ipomoea carnea is a gregariously growing short shrub available all over the world. The plant is native of South America and was introduced in to India as an ornamental plant. Cellulose content of this shrub is over 55% and lignin content is about 17% which indicates it is a fibrous material and can be used as filler for making light weight polymer composite which provides an effective means of utilization of a large quantity of this diffuse shrub. Literature indicates that no significant work has been done on this shrub other than its stems are used for developing housing element in rural India without any pre-treatment resulting non-durable structure. Hence in this present work an attempt has been made to prepare and study the mechanical and abrasive wear behaviour of Ipomoea carnea reinforced epoxy composite, with different concentration of particulates.
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Kemmer, Helerson Alexandre. "Investigation of the friction behavior of automotive brakes through experiments and tribological modeling /." 2002. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=013185550&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Повний текст джерела
45
Wen-Hsien, Kao, and 高文顯. "The Tribological Characteristic and Cutting Performance Investigation of Metal-Diamond Like Carbon Films." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/13541122884628376247.
Повний текст джерелаАнотація:
博士國立成功大學
機械工程學系
88
This study employed the PVD process to deposit ceramic coatings of single layer TiN and CrN, binary layer TiN/TiCN and CrN/CrCN, multilayer TiN/Ti/TiN and TiN/TiCN/TiN on tungsten carbide disks and inserts. Also, a series of Me-DLC (Tix%-C:H/TiC/TiCN/TiN and Crx%-C:H/CrC/CrCN/CrN) coatings with varying thickness and different ratios of x% metal (Ti and Cr) target “poisoning” on tungsten carbide disks and inserts by Unbalanced Magnetron (UBM) sputtering process. Counterbodies of AISI 1045 steel cylinder, AA7075aluminum cylinder, AA 6061 aluminum cylinder and bronze cylinder were used in cylinder-on-coated disk, line-contact wear mode under dry condition; a counterbody of AISI 52100 steel ball was used in ball-on-coated disk, point-contact wear mode, under both dry and lubricated conditions. All wear tests were conducted with a reciprocating machine (SRV). Actual milling tests were also performed to identify the cutting performance. After the tests, the most suitable coating for various counterbodies and test environments were selected. Notably tribological performance was observed for Me-DLC coated disks under dry condition due to the carbon- rich transferred layers formed between the contact interfaces. For example, the optimum coatings are composed of an intermediate layer of TiC/TiCN/TiN and a top layer of Tix%-C:H with x £ 20%. These coatings have an excellent wear resistance and a low friction coefficient when paired with a carbon steel or bronze. These pairs also are marked by the mildly wear of the counterbodies of AISI 1045 steel and bronze. The excellent cutting performance for optimized Me-DLC coated tools can replace ceramic coated tool operations under dry cutting process. The results indicate that Ti30%-C:H/TiC/TiCN/TiN (Ti30%-C:H thickness 2.5mm) coated tool possesses excellent wear resistance and produce good machined surface roughness under dry milling AA 7075 aluminum. Furthermore, the excellent cutting performance for Ti30%-C:H/TiC /TiCN/TiN coated tool under dry process can replace ceramic coated tool under cutting fluid process. It is a “green” manufacturing cutting operations. And also, the Ti30%-C:H/TiC/TiCN/TiN coated tool possesses excellent cutting performance for milling AISI 1045 steel under dry conditi
46
HSU, CHIH-I., and 許志義. "Investigation on Preparation and Tribological Properties of Electroless Ni-P Based Composite Coatings." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77046996180664710849.
Повний текст джерелаАнотація:
博士國防大學理工學院
國防科學研究所
104
Electroless Ni-P coating has excellent mechanical properties, which wide range of applications, such as automotive, aerospace, machinery, integrated circuits, printing and chemical industries. It enables the material to achieve corrosion resistance, abrasion resistance, heat resistance, and prolong the service life of the material. It was found that the hardness and wear resistance of electroless Ni-P coatings can be improved by the functional particles co-deposition. So now each country has been put into research and development. In the beginning of this study for the properties of wear resistant Ni-P/Al2O3 and lubrication Ni-P/PTFE composite coatings were discussed. Secondly, choicing temperature resistance and lubrication hexagonal boron nitride(BN(h)) particles through surfactant by electroless way to successfully co-deposited on Ni-P coating, and exploring the properties of Ni-P/BN(h) composite coating before and after heat treatment. Finally, by the way of experimental design approach to develope Ni-P/Al2O3-BN(h) composite coating, and to compare a series of properties of Ni-P/Al2O3 and Ni-P/BN(h) composite coating. Wherein the test items include electron probe x-ray microanalyzer (EPMA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), atomic force microscope (AFM). The wear behavior of the coatings was investigated using a ball-on-disk wear tester, and the corrosion behavior were evaluated through polarization curves in 3.5 wt.% NaCl aqueous solution at the room temperature. The results show that (1)Ni-P/Al2O3 composite coatings help to improve the mechanical properties and wear resistance. (2)Ni-P/PTFE composite coating through a suitable heat treatment at 340℃ for 30min can effectively enhance the mechanical properties and maintain lubrication of PTFE particles, that significantly improved the wear resistance and lubricating property. (3)Self-lubricating Ni-P/BN(h) composite coating through surfactant to increase BN(h) particles uniform distribution, while strengthening the mechanical properties and increased density. When the heat treatment at 400℃, the wear resistance and lubricating property of composite coating is more further improvement. (4)Ni-P/Al2O3-BN(h) composite coating has successfully complete the development, when the content of Al2O3 and BN(h) were 6.3vol.% and 9.1 vol.%, which can simultaneously exhibit better wear resistance and lubricating properties.
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Nayak, Prajapati. "Investigation in to Mechanical and Tribological Behaviour of Orange Peel Reinforced Epoxy Composite." Thesis, 2015. http://ethesis.nitrkl.ac.in/7999/1/674.pdf.
Повний текст джерелаАнотація:
Over the last century, polymers have emerged as one of the most indispensable components used in everyday life, epoxy or poly-epoxide being one such example. Until recently, synthetic filler materials have been the preferred choice for reinforcement of epoxy to improve its mechanical and tribological properties. However, natural fibers are emerging as suitable alternatives to synthetic materials for obvious reasons. Several research efforts have been put to study the effectiveness of natural fiber-based materials on the mechanical behaviour of epoxy composites, focusing mainly on fibers and their weight percent within the composites. In the present work, an attempt has been made to prepare and characterize orange peel (particulate) reinforced epoxy composite for the tribological application. Composites are having 10, 20 and 30% weight fraction of orange peel were made using hand layup method and were tested on a standard pin on disc wear tester. All the test have been carried out according to the ASTM standards.
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Rajkonwar, Amit. "Investigation into mechanical and tribological properties of Lantana Camara particulate reinforced epoxy composite." Thesis, 2017. http://ethesis.nitrkl.ac.in/9688/1/2017_MT_215ME6235_ARajkonwar_Investigation.pdf.
Повний текст джерелаАнотація:
Natural fibers are emerging as suitable alternatives to synthetic materials for reinforcing material in polymers such as epoxy due to their advantages such as environment
friendliness, biodegradibility,renewability and cost effectiveness.Due to such advantages,further exploration of new natural fibers as a filler material in polymer matrix
composites for different tribological applications is needed. Lantana camara is one such abundant natural resources whose potential as filler material in polymer composite has not been explored to such a level till date. The present experimental study aims at studying abrasive wear behaviour of lantana camara powder reinforced epoxy composites and their mechanical properties such as tensile and flexural strength .Composites having 10, 20 and 30 wt fraction of lantana camara powder were made using hand layup method in a steel mould to study the abrasive wear behaviour on a pin on disc wear tester. It was found that both the abrasive wear resistance and strength of the composite samples can be significantly improved by the incorporation of lantana camara particulates into epoxy . At 20 wt. fraction of lantana camara,both the wear resistance and strength of the composite were found to be optimum.However, excessive addition of particulate(30%)results in increase of wear rate as well as lowering of strength. SEM studies were conducted for the wear out samples to study the failure nature at the microscopic level.XRD analysis was also performed to study the crystallographic structure of lantana
camara powder.
49
Ho, Shu-Ching, and 何淑靜. "Investigation of the tribological behavior of copper/phenolic resin-based semi-metallic friction materials." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/90636986974054761402.
Повний текст джерелаАнотація:
博士國立成功大學
材料科學及工程學系碩博士班
93
The present work is the study of a copper/phenolic resin-based semi-metallic friction material. To improve the tribological behavior of the friction material at higher temperature, we used different processing parameters, different fiber additions, heat treatment (semi-carbonization) conditions, different matrix components and different matrix types. We also discussion the effect of each way on mechanical and tribological behavior of a copper/phenolic resin-based semi-metallic friction material. We hope to development a semi-metallic friction material which has superior heat resistance and best tribological behavior. The effect of the processing parameters indicate that the best parameters of hot press is at temperature 180 ℃ and under the pressure of 100 kg/cm2. The optimal post-cure rate is 1 ℃/min when temperature is lower than 160 ℃ and 0.5 ℃/min when temperature between 160-180 ℃. The results of fiber addition show that compared to the fiber-free material, materials containing copper and brass fibers have higher compressive strengths. Except cellulose, all fiber-added materials exhibit higher average COF values than that without fibers. The copper fiber-added material has the smallest wear. Among all fibers the copper fibers appear to be the best candidate due to its relatively high and stable COF as well as low wear. The results of carbonization show that a lower carbonization rate leads to materials having a higher compressive strength and hardness, as well as fewer cracks. Heat-treating to higher temperature causes both values to decline. Both the friction coefficient and wear are increased with an increasing carbonization temperature. The material carbonized to 600 ℃ exhibits optimal tribological performance. Carbonized samples demonstrate far better high-temperature heat/oxidation resistance than that of non-carbonized samples. The results of phenolic content show that the materials with 50 vol% resin exhibited the maximum compressive strength, hardness and increase in density after semi-carbonization. Among all materials, R5 demonstrated the greatest potential with a high and stable COF value and reasonably low wear. The results of different matrix type show that that the pitch-matrix materials exhibit lower compressive strength and hardness values than those of the resin-matrix materials after semi-carbonization. Compared the results of COF and weight loss, the resin-matrix materials can maintain the COF(about 0.35) at a high temperature (about 300 ℃) and the weight loss of the resin- matrix materials only half of the pitch-matrix materials. The resin-matrix materials demonstrate far better high-temperature heat/oxidation resistance than the pitch-matrix materials. The results of fiber addition and semi- carbonization show that all fiber-added materials exhibit lower compressive strength and hardness values than those without fibers after semi- carbonization. The metal fiber-added materials have the best effect in increasing initial COF. Except cellulose, all fiber-added materials exhibit higher wear values than those without fibers. Compared to fiber-added materials, the fiber-free material appears to be the best candidate due to its relatively high mechanical properties and stable tribological behavior after semi-carbonization. Experimental results indicate that the semi- carbonization can improve the high-temperature heat/oxidation resistance and tribological behavior of a copper/phenolic resin-based semi-metallic friction material without fiber addition.
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Garg, Gaurav Kumar. "Investigation into Mechanical and Tribological Behaviour of Hollow Glass Microsphere (HGM) Reinforced Epoxy Composite." Thesis, 2015. http://ethesis.nitrkl.ac.in/8000/1/675.pdf.
Повний текст джерелаАнотація:
In the present work hollow glass microspheres (HGMs) filled epoxy composite with filler content from 0 to 20 wt. % were prepared in order to improve the abrasive wear and mechanical properties of epoxy. Tensile strength and impact strength were determined experimentally. Abrasive wear test was conducted using pin-on-disc wear tester. Composites having 0, 10, 15, and 20 weight fraction of HGM filled epoxy have been prepared in the laboratory by using a self-designed mould. All the experiments were conducted as per ASTM standard. It was found that as the reinforcement (HGM) increases from 0 to 20 wt. % the wear resistance as well as mechanical properties of composite increases. The enhancement in these properties is related to strong bonding between the HGM and epoxy which might have happened due to formation of an interphase between the HGM and epoxy-matrix. SEM (scanned electron microscope) studies were also carried out to know the fracture behaviour of the composite.