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Young, William G. "Tooth wear /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17715.pdf.
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Done, Vamshidhar. "Numerical modeling of dry wear : Experimental study of fretting wear, fretting wear simulations with debris entrapped and industrial applications of fretting wear models." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI137.
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De nombreux modèles numériques sont proposés dans la littérature en utilisant des méthodes d'éléments finis et d'éléments finis discrets pour étudier l'usure par frottement, ils incluent à peine l'effet des débris d'usure. Ces modèles étant coûteux en termes de calcul, simuler un grand nombre de cycles d'usure par frottement n'est pas réalisable dans la pratique. Une nouvelle méthodologie est proposée qui ne nécessite que des propriétés de matériau en vrac comme les coefficients de frottement / usure et utilise des méthodes semi-analytiques pour simuler l'usure par frottement avec des débris piégés. Dans cette approche, les débris sont supposés être attachés à l'une des surfaces pendant le processus de fretting. Les résultats obtenus à partir de cette approche ont été comparés avec des expériences de fretting. La méthode proposée permet de saisir la profondeur d'usure et la largeur des cicatrices, et les résultats sont très proches de ceux observés dans les expériences. L'assemblage des soupapes des moteurs à combustion subit une usure par frottement en raison d'un phénomène complexe impliquant une rigidité structurelle et une tribologie de contact. L'usure des soupapes a de nombreux effets néfastes sur les performances du moteur. Il provoque une récession de la soupape entraînant des changements dans les connexions du mécanisme d'entraînement de la soupape, ce qui perturbe l'ouverture et la fermeture des soupapes. Avec des normes d'émission strictes, l'utilisation de lubrifiant pour réduire la friction au contact est limitée. Si l'usure à travers la circonférence n'est pas uniforme, il y aura une fuite de gaz et le moteur donne moins de puissance. Il est nécessaire de bien comprendre la raison de l'usure des soupapes et de développer un modèle numérique capable de prédire l'usure par frottement de la soupape pour le nombre d'heures de fonctionnement donné. Des expériences ont été réalisées pour comprendre le mécanisme d'usure et calculer les coefficients d'usure qui peuvent être utilisés dans le modèle numérique. Un modèle d'usure numérique est construit qui capture la rigidité structurelle de l'ensemble de soupape et le mécanisme d'usure au contact du siègeMany numerical models are proposed in the literature using finite element and finite discrete element methods to study fretting wear, they barely include the effect of wear debris. These models being computationally expensive, simulating large number of fretting wear cycles is not practically feasible. A new methodology is proposed which needs only bulk material properties like friction/wear coefficients and uses semi-analytical methods to simulate fretting wear with entrapped debris. In this approach, debris are assumed to be attached to one of the surfaces during the fretting process. The results obtained from this approach were compared with fretting experiments. The proposed method permits to capture the wear depth and scar width, and results are very close to that observed in the experiments. Valve assembly of combustion engines undergo fretting wear due to a complex phenomenon involving structural stiffness and contact tribology. Valve wear has many detrimental effects on the engine performance. It causes valve recession leading to changes in connections of valve drive train in turn disturbing the opening and closing of valves. With stringent emission norms, usage of lubricant to reduce friction at the contact is restricted. If the wear across the circumference is not uniform, there will be leakage of gas and the engine gives lesser power output. There is a need to thoroughly understand the reason for valve wear and develop a numerical model that can predict valve fretting wear for the given number of operating hours. Experiments were performed to understand the wear mechanism and derive wear coefficients that can be used in the numerical model. A numerical wear model is built that captures structural stiffness of the valve assembly and wear mechanism at seat contact
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Oosthuizen, Gert Adriaan. "Wear characterisation in milling of Ti6Al4V : a wear map approach." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5426.
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Thesis (PhD (Industrial Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Information on the milling of Ti6Al4V is limited; with most studies concluding that it is not possible to obtain a significant increase in the material removal rate (Qw). Tool wear maps can be a diagnostic instrument for failure analysis. Cutting speed (vc), maximum un-deformed chip thickness (heMax) and the radial immersion percentage (ae/Ø %) are the key variables in understanding the milling of titanium alloys. The objective of this research study was to construct tool wear maps for the milling of Ti6Al4V. This will form the foundation of understanding the cutting demands on the tool, in order to analyse the main wear mechanisms. Remedial actions, which are developed by tool suppliers, can be considered and integrated via this understanding of the failure modes and related mechanisms. Firstly, experimental data from background studies, literature and industry on wear rates and wear mechanisms pertaining to the milling conditions was gathered to construct the tool wear map. Mathematical models describing the wear behaviour for these conditions were also investigated. Secondly, work piece failure maps have been superimposed onto the tool wear maps constructed to understand the global failure boundaries. Experimentation was carried out to validate the constructed maps. The tool wear map could then be used to discuss the observed effects and consider remedial actions. Cutting speed corresponds to the magnitude of the thermal load and heMax represents the mechanical load. The ae/Ø % defines the duration of the exposure to the thermal load at the edge of the cutting tool. This investigation has shown the following issues to be of importance when considering tool performance via the tool wear map approach: 1. The key to designing tool wear maps is to identify the most economic Scheduled Replacement Time (SRT) for the specific components. Knowing the correct SRT makes it possible to optimize the milling conditions so that the cutting tool wears gradually under the cutting conditions, and lasts longer than the economic SRT. 2. Increased vc will decrease tool life (TL). However, in low transverse rupture strength tools there may be a minimum vc below which mechanical overload may occur. Similarly, a local maximum TL (a sweet spot) may exist if there is a phase change in the work piece material. 3. Increased heMax will decrease TL. However, heMax must be kept below a maximum critical value to avoid mechanical overload, but above a minimum critical value to avoid work hardening. 4. Increased ae/Ø % will decrease TL. The best balance of high Qw and economic TL is found with ae/Ø between 30-40% for rough milling. In finish milling the radial cut is limited to 1 mm finishing stock of the work piece. This study revealed the following important factors when considering work piece failure in the milling of Ti6Al4V: 1. Increased vc will reduce the cutting resistance of the work piece and increase Qw. However, vc must be kept below a maximum critical value to avoid work piece material burn, but above a minimum critical value to avoid burring and poor surface finish, due to tool build-up and chip jamming. 2. Increased heMax will increase the cutting resistance of the work piece and increase Qw. The heMax must be kept below a maximum critical value to avoid poor surface finish, poor flatness and parallelism (due to work piece bending). Likewise, heMax must be kept above a minimum critical value to avoid work hardening and burring. The constructed tool wear maps are validated with experimental work. This research work identified safe zones to productively mill Ti6Al4V, while producing components with a sufficient surface integrity.
AFRIKAANSE OPSOMMING: Inligting rondom freeswerk van Ti6Al4V is beperk en volgens meeste studies is dit nie moontlik om ‗n wesenlike toename in die materiaal verwyderingstempo (Qw) te behaal nie. Snybeitel verwerings kaarte kan ‗n diagnostiese hulpmiddel wees tydens analisering van snybeitels. Snyspoed (vc), maksimum onvervormende spaanderdikte (heMax) en radiale snitdiepte persentasie (ae/Ø %) is die sleutel veranderlikes om die freeswerk van Ti6Al4V beter te kan verstaan. Die doel van die navorsingstudie was om snybeitel verweringskaarte vir die freeswerk van Ti6Al4V te bou. Die werk vorm ‗n fondasie om die eise van freeswerk op die snybeitel beter te verstaan. Sodoende kan die hoof verweringsmeganismes analiseer word. Regstellende aksies wat deur snybeitel vervaardigers ontwikkel is, was ondersoek en integreer met die huidige kennis rondom die falingstipe en verwerings meganismes. Aanvanklik was eksperimentele data van agtergrond studies, literatuur en industrie oor die verweringstempos en -meganismes rondom die freeswerk van Ti6Al4V versamel. Hiermee is verweringskaarte gebou. Wiskundige modelle wat die verwering kan beskryf was ook ondersoek. Daarna was werkstuk falingskaarte integreer met die ontwikkeling van die snybeitel verweringskaarte om sodoende die grense in geheel te verstaan. Eksperimentele werk was gedoen om die snybeitel verweringskaarte se uitleg te toets. Sodoende kon die snybeitel verweringskaarte gebruik word om die gedrag van die snybeitel te bespreek en regstellende aksies te ondersoek. Snyspoed (vc) stem ooreen met die grootte van die termiese lading en heMax verteenwoordig die grootte meganiese lading. Die ae/Ø % omskryf die tydperk van blootstelling aan die termiese lading op die snyrand. Die ondersoek het bewys dat die volgende faktore belangrik is wanneer snybeitel prestasie met die snybeitel verweringskaart evalueer word: 1. Die sleutel tot die ontwerp van snybeitel verweringskaarte is om die mees ekonomies beplande vervangingstyd (SRT) vir spesifieke komponente te identifiseer. Sodoende is dit moontlik om die frees toestande te optimaliseer, waaronder die snybeitels geleidelik sal verweer onder die eise en vir ‗n langer tydperk as die ekonomiese SRT sal kan sny. 2. Toename in vc sal snybeitelleeftyd (TL) laat afneem. Snybeitels met ‗n lae dwarsbreuksterkte, kan ‗n minimum vc hê waaronder meganiese oorlading plaasvind. Terselfdertyd, kan ‗n maksimum TL (‗n ―sweet spot‖) bestaan as daar ‗n fase verandering in die werkstuk materiaal plaasvind. 3. Toename in heMax sal TL laat afneem, maar moet laer as ‗n maksimum- en hoer as ‗n minimum kritiese waarde wees, om sodoende meganiese oorlading en werksverharding onderskeidelik te vermy. 4. Toename in ae/Ø % sal TL laat afneem. Die beste balans tussen TL en ae/Ø % is gevind met ae/Ø % tussen 30-40% vir growwe freeswerk. In afrondingsfreeswerk is die radiale snit beperk tot 1 mm van die oorblywende werkstuk. Die ondersoek het bewys dat die volgende faktore belangrik is wanneer werkstukfaling in ag geneem word met snybeitel verweringskaarte: 1. Toename in vc sal die werkstukweerstand geleidelik verminder en Qw laat toeneem. Ongelukkig is vc beperk tot ‗n maksimum kritiese waarde om werkstukfaling te voorkom weens ‗material burn‘. Die snyspoed moet ook hoër as ‗n kritiese waarde wees om werkstukklitsing en swak afronding weens spaander probleme te vermy. 2. Toename in heMax sal die werkstuk weerstand geleidelik vermeerder en Qw laat toeneem. Die heMax is beperk tot ‗n maksimum kritiese waarde om swak werkstuk afronding, weens die buiging van die werkstuk, te vermy. Terselfdertyd moet heMax hoër as ‗n kritiese waarde wees om werkstukverharding en -klitsing te voorkom. Die saamgestelde snybeitel verweringskaarte was bekragtig met eksperimentele werk. Die navorsingswerk het veiligheidsareas identifiseer om Ti6Al4V produktief te frees, sonder om die werkstukoppervlak krities te beïnvloed.
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Uusaro, Alexandra. "Analysis of wear life and mechanical stability for wear steel." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86927.
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This thesis work is carried out in collaboration with Olofsfors AB. They manufacture steel products such as tracks and chains for forest machines and wear steel for plows and graders. The focus of this project is on wear steel. The aim with this project is to obtain a better understanding of mechanical stability and wear on different types of wear steel. This knowledge can then be used to prolong the life cycle in future products. This project was divided into two parts where the first one concerns wear steel for plows. In this part a comparison between six different steels was conducted using mechanical tests. The steel type will not be specifed in this report but will instead be denoted with the letters A to F. The tests used were rubberwheel abrasion tests to investigate wear resistance, Charpy-V impact tests in cold temperatures to find crack resistance and tensile tests in order to analyze tensile properties. Steel F was not a part of the rubber wheel abrasion test since a specimen with correct dimensions could not be manufactured from the product due to its special geometry. The second part of the project was for Olofsfors Bruxite grader edges. The objective with this part was to build a model to predict wear on edges using Numerical modeling. The multiphysics program LS-DYNA was used. The environment for the grader is a mining site giving a very rough gravel road. Discrete element method was used for computation of the granular material of the road and the fnite element method was used on the grader. The wear calculations were made with Archard's wear law. The road was built up in two different ways, in the first model loose discrete element spheres were used. In the second model one layer of bonded discrete element spheres was used with a top layer of loose spheres.Different meshes and loads were also tested.
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Franklin, Francis James. "Modelling mild wear." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312780.
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Chen, Yu-Chieh. "Versatile bridal wear." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1345.
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Thesis (BTech (Fashion Design))--Cape Peninsula University of Technology, 2010In the 19th and 20th Century, products were manufactured with little concerns for the environment. The result of this was an over flowing of low quality products and a high elimination rate, especially in the fashion industry where constant change is the nature of the business. Particularly in bridal wears, the sustainability is deficient and practicality is limited. bridal garments would only be worn once and are usually highly priced. The purpose of this research is to explore whether consumers are willing to contribute and make a difference to our environment by opting for versatile bridal wear. In order to obtain information regarding the bridal industry of Cape Town. a qualitative approach was applied to ensure that the end products will meet customer needs. Store visits and informal interviews were used as the primary methods. and Internet and magazines were used as secondary methods to gain relative information about the market. The information collected. regarding modem women's opinions on the concept of an interchangeable bridal range, current fashion trends and the concept of Slow Design, forms the foundation to the development of my range - versatile bridal wear. The entire range consists of 14 garment pieces that are interchangeable to form 6 or more looks. This allows the wearer to dress up according to their desires. As a result, these dresses are reusable and thus overcoming the problem of costly garments. which are only worn once.
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Kronqvist, J. (Joel). "Wear-resistant materials." Bachelor's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201604211527.
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Materials used in wear-resistant applications are exposed to heavy loads and different environmental circumstances which generate mechanical wear and corrosion. By choosing the most suitable materials for the correct applications, you can affect the lifetime of the machine and create substantial cost savings.
This thesis displays wear-resistant steels but also other wear-resistant materials, including irons, ceramics and polymers. Use of the materials is divided by the application. For dry applications with mechanical wear carbon steels are the optimal choice and for corrosion and tribo-chemical wear stainless steel is the correct material.
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Hilt, Devin O. "Wedding - To - Wear." Kent State University Honors College / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1493989886206976.
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Bautista, Fernández Christian Hilario, Allende Angel Rafael Delgado, Trucíos Carolina Fuentes Rivera, and Franco Sarita Liliana Rentería. "INKA Sport Wear." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2018. http://hdl.handle.net/10757/624698.
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En el Perú la práctica por la natación crece cada vez más, no solo por la afición que causa entre las personas que lo practican, sino también por los beneficios que ofrece, al ser uno de los deportes más completos que existe. Las diferentes academias y/o institutos deportivos no se encuentran exentas a este crecimiento, tomando en cuenta las nuevas tendencias como la práctica de natación en mujeres embarazadas. Ante ello, es necesario contar con una prenda que se adecue a las necesidades específicas de cada cliente tanto en talla como en diseño frente a la constante demanda. El mercado actual carece de esta diversidad al ofrecer tallas únicas y de costo elevado al que no todos pueden acceder, restringiendo la práctica de este deporte. En ese sentido, nace Inka Sport Wear, como una solución que busca satisfacer las necesidades de sus clientes a través de la comercialización de ropa de baño con diseños innovadores y personalizados a un precio asequible manteniendo la comodidad, calidad y durabilidad del producto.In Peru, the practice of swimming is constantly increasing, not only as a hobby in their fans, but also for the benefits this sport offers as it is considered one of the more complete sports. The different sport academies and/or institutions are also part of this increase, considering the new tendency of swimming in pregnant. Therefore, it is necessary to have a swimming suit for facing the specific needs of each client both in size and design of the product caused by the constant demand. The current market lacks of this variety offering unique size and costly products not everyone may purchase which restricts its practice. In this sense, we launched Inka Sport Wear as an inexpensive solution to satisfy the different needs of their clients with innovative, customized swimming suit keeping comfort, quality and durability.
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Lim, S. C. "Wear mechanisms with particular reference to the wear of sintered materials." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372885.
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De, Villiers Danielle. "Accelerated wear protocols for understanding clinical wear in modern hip prostheses." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/7981.
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Success of total hip replacements is well reported however, failures as a result of wear processes and the biological response to these products continue to challenge the orthopaedic community. Lately, corrosion of metal surfaces as well as wear particles have seen particular interest with elevated blood cobalt levels widely reported in patients receiving metal-on-metal (MoM) hip replacements. Some instances have also reported this in patients with metal-on-polyethylene (MoP) components and these corrosion products are believed to contribute to hypersensitivity reactions reported. This thesis considers wear and cobalt release in MoP and MoM hip bearings tested under standard and challenging hip simulator conditions and includes an exploration of novel bearing coatings to reduce cobalt release. The incorporation of silver into these coatings may be sufficient to produce an antibacterial response, reducing the risk of mid-term infections, another reported cause of failure. Polyethylene wear was low under standard and clinically relevant adverse conditions in 28mm and 52 mm diameter MoP bearings (less than 35 mm3/mc). Cobalt release was measurable in 28 mm diameter MoP bearings (51 ppb/mc) with higher levels produced in large 52 mm diameters (123 ppb/mc), the first time this has been reported, although cobalt release was substantially less than that observed in MoM bearings (6909 ppb/mc). Alumina abrasives introduced in the lubricant substantially damaged MoP bearings, increasing the cobalt release to 70,690 ppb after 1 mc, greater than found after edge loaded MoM bearings (19,240 ppb). The removal of these particles still produced elevated cobalt levels compared to standard conditions and increased polyethylene wear to 435 mm3/mc. A chromium nitride (CrN) coating in MoP bearings was resistant to this abrasive damage showing no delamination in the coating, with negligible cobalt released after 7.04 mc (153 ppb) and maintained a polyethylene wear rate below 20 mm3/mc. Silver CrN coatings on both bearing surfaces of MoM components prevented cobalt release under standard conditions, with silver release after 0.17 mc up to 3,720 ppb in high silver surface coatings, although the wear was relatively high (5.24 mm3/mc). A silver CrN coating with a low concentration of silver at the surface reduced wear and was resistant to 5 mc of edge loading. It generated 241 ppb of cobalt and maintained comparable steady state wear rates (0.65 mm3/mc) to the uncoated metal while releasing 18,786 ppb silver which may be sufficient to be an effective anti-microbial agent. These coatings may provide potential clinical benefits in MoP and MoM bearings by reducing both wear and cobalt release in ideal and adverse conditions. There may also be beneficial wear products in the form of silver, although further testing of optimised coatings is required.
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Lindsey, Julie E. (Julie Elizabeth). "The Perception of Western Wear Status Symbols Among Western Wear Consumers." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc279336/.
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This study determined whether an association exists between the perception of western wear status symbols and demographic characteristics {i.e., gender, age, income, and
education level) among Texas American Paint Horse Association members.
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Russell, Serena Louisa. "Friction, wear, wear debris and functional biocompatibility of cartilage substitution biomaterials." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/12742/.
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The friction, wear and biological response to hydrogels, thermoset and thermoplastic polyurethanes were investigated in order to determine their suitability as potential cartilage substitution biomaterials. A single station pin-on-plate friction rig was utilised to determine the friction properties of these materials when articulated against articular cartilage plates and stainless steel plates. These materials were also reciprocated against stainless steel plates with smooth and rough surfaces using a six station multidirectional wear rig to generate clinically relevant sized wear particles which were characterised in terms of particle number and area as a function of size. Aseptically generated wear particles from the thermoset and thermoplastic polyurethanes were generated utilising a single station pin-on-plate wear rig and cultured with peripheral blood mononuclear cells to establish their biological activity by assessing the release of four cytokines (tumour necrosis factor-alpha, interleukin-lβ, interleukin-6 and interleukin-8) using an enzyme-linked immunosorbent assay. Friction tests demonstrated that articular cartilage (articulated against itself) exhibited a low coefficient of friction which was concurrent with the literature. The thermoplastic polyurethanes and hydrogels (against articular cartilage) exhibited statistically similar friction characteristics compared to articular cartilage against itself, however, the hydrogels generated considerable wear. In contrast, the friction characteristics of the thermoset polyurethanes were significandy higher than the friction of articular cartilage against itself. When wear particles were generated against stainless steel plates with smooth and rough surfaces, it was clear that the largest percentage number of particles were either < 0.1 or 0.1-1.0 11m in size, however, the percentage area of these particles was more variable and was either in the 0.1-1.0 μm, 1-10 μm or > 10 μm size range. Diprane SOD was the least biologically active material, as cells from two donors out of three were stimulated to release elevated levels of cytokines. Diprane SOD and Corethane 5SD were the only two materials to stimulate cells from donors to significandy release three cytokines out of four. All other materials stimulated an elevated level of all four cytokines from cells from all three donors.
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Dahlström, Alexander. "Wear mechanisms in austenitic stainless steel drilling : A comprehensive wear study." Thesis, KTH, Materialteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175771.
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This thesis is meant to serve as part of a competence platform for future product development projects at Sandvik Coromant AB, Solid Round Tools Department, Västberga, Sweden. The project objective is to gain generic knowledge of the wear mechanisms that restrict tool lifetime when drilling austenitic stainless steel. Thus, identifying if the weakest link of the tool is located within the coating, the coating adherence or in the strength of the substrate. A theoretical review of the work-piece and tool materials has been conducted as a background, along with definition of tool geometry and process parameters. Furthermore, the review includes chemical and process design effect on mechanical properties of the austenitic stainless steel, TiAlN coatings and cemented carbide substrates. Additionally, the basic principles of the wear mechanisms and wear types that are specific to drilling have been reviewed. During the experimental procedures both solid and exchangeable tip drills from cemented carbide with multilayered PVD TiAlN coatings were tested. Two series of tests were conducted, the first series aimed to identify wear type dependency on cutting speed, focusing on wear of the tool margin. The second test series was performed to map the wear progression depending on distance. Analyses including identification the main wear mechanism, quantification the amount of wear, identify wear location on the tool, crack investigation and WDS analysis of chemical wear. Adhesive coating wear was found on the tool margin at an early stage. The adhesive wear rapidly progressed into a stable intermediate stage. Leaving the substrate exposed and more susceptible to other wear types resulting in crack and oxide layer formation.
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Mussa, Abdulbaset. "Wear characterization and wear mapping of a coated cutting tool : Development of cutting tool test fixture and wear testing." Thesis, Karlstads universitet, Science, Mathematics and Engineering Education Research (SMEER), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37790.
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Wear mechanisms of the cutting tools are well investigated worldwide. Usually researchers use the cutting process itself, turning by single point cutting, as their investigation method, which includes turning a metal cylinder with a pre-selected work-material and predetermined cutting conditions. Thereafter the tool worn surface is examined by scanning electron microscopy in order to characterize the tool wear mechanisms and tool failure. However, this may be the most appropriate way to investigate the wear mechanisms which occur during machining since it simulates the real operation. Metal cutting involves extreme conditions such as high temperature and high-pressure and the different condition results in different wear modes on the insert’s surface. The wear modes are overlapping and the transition boarder between them are not sharp making it difficult to obtain a detailed information of wear mechanisms. Because of these reasons many researchers try to refine the machining to a single condition e.g; high pressure, at the laboratory level in order to characterize the wear mechanisms and to get a more detailed information. In this thesis the wear tests of the cutting tool are performed by using a slider-on-flat-surface (SOFS) wear tester. SOFS involves a normal load, which applies to the sample and a tangential force that enables the sliding of the sample against a counterface. To enable conducting the wear tests in SOFS a newly design of tool holder was prepared. The wear tests were performed at different contact conditions and the stainless steel EN 1.4310 was used as the counterface material. After the tools were tested, the worn surface of the tool was examined by optical light microscopy and scanning electron microscopy in order to identify the wear rate and wear mechanisms. At low load the dominating wear mechanism was adhesive wear. The adhesive wear was induced by material pick-up during sliding i.e. material from the counterface was transferred to the insert’s surface. Further sliding results in delamination of the insert surface and removal of a part of the coatings material. At high load the dominating wear mechanism was a combination of severe adhesive wear and fracture of the coating material. The fracture of the coating material occurred because of overloading. Coating defects promote crack formation under high load and these cracks propagate through the coating during sliding movement and result in microchipping of the coating material. This procedure does not simulate the metal cutting but it still gives an understanding of the behavior of the coating material when it is exposed to a high mechanical stress.
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Hernandez, Sinuhe. "High Temperature Wear Processes." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16827.
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Moving machine assemblies are increasingly exposed to extreme operating conditions involving high temperatures owing to demands on higher power densities, high performance/efficiency and extreme environments. The changes in surface and near surface properties of contacting surfaces caused by exposure to high temperature and deformation govern the occurrence of friction, wear and material transfer of the tribological system. However, these changes have not been thoroughly investigated. In order to enable development of new products and processes, there is a need for new knowledge pertaining to tribological phenomena occurring at elevated temperatures.One of the most commonly used engineering materials is steel as it offers a good compromise between performance and cost even at high temperatures. For example, prehardened (quenched and tempered) tool steels are commonly used in hot forming dies can also be employed in other technological applications involving elevated temperatures. Although the research pertaining to hot stamping, and high temperature tribology in general, has significantly grown during the last years there are still knowledge gaps that need to be bridged. Adhesion and abrasion have been identified as the most dominant wear mechanisms in high temperature tribological systems but the detailed understanding of the mechanisms is still inadequate.The objective of this work is therefore to obtain a deeper understanding of the tribological phenomena associated with adhesion and abrasion that takes place at high temperatures. Unidirectional sliding wear tests have been conducted in order to investigate the influence of contact pressure and temperature on the wear and friction characteristics of tool steel and boron steel pair. Tribological studies involving boron steel, tool steels and heat-treated high-Si steels in a three body abrasive environment were also carried out with a view to explore the effect of temperature on the wear rate, wear mechanisms and to correlate this with material properties like hot hardness and toughness.The results from the unidirectional sliding tests showed that the frictional behaviour of tool steel and boron steel is load and temperature dependent. In general the friction coefficient decreases as both temperature and load are increased as a result of the formation of oxide layers. At temperatures above 200 °C, the compaction and sintering of these layers led to the formation of a wear protective glaze layer. Consequently, the wear rate for both materials decreased at elevated temperatures. Additionally, a friction and wear mechanisms map was developed for the investigated materials.In the case of abrasive wear tests, the results showed that the main wear mechanism presented for each material varied with temperature. In general, a transition from micro-ploughing to a combination of micro-cutting and micro-ploughing was present. The tool steels and boron steel showed a decrease in wear rate in the range of 100 to 400 °C compared to that at room temperature. This was attributed to the toughness in case of the tool steel and the formation of a protective tribolayers for the boron steel. Above 400 °C the wear rate increased for these three materials mainly due to the recovery and recrystallization processes. The wear rate of the high-Si steels increased with testing temperature. At 500 °C, these steels had the same hardness and the differences in wear were attributed to the changes in the material toughness.Godkänd; 2014; 20140408 (sinher); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Sinuhe Hernandez Ämne: Maskinelement/Machine Elements Uppsats: High Temperature Wear Processes Examinator: Professor Braham Prakash, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Assoc. Prof. Ph.D; Head, Metallic Materials and Tech. Dept. Bojan Podgornik, Institute of Metals and Technology, Ljubljana, Slovenia Tid: Fredag den 16 maj 2014 kl 10.00 Plats: E231, Luleå tekniska universitet
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Cutler, H. Bernice. "Ready to wear architecture." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39645.pdf.
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Ting, Bond-Yen. "A thermomechanical wear theory." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/17629.
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Franco, Jr Adolpho. "Erosive wear of alumina." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320591.
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Ding, Jian. "Modelling of fretting wear." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275169.
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Sharp, Steven John. "The wear of polymers." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627424.
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Martinsson, Johan. "Wear of Grate Plates." Thesis, KTH, Materialvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160603.
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This report describe the wear of the protruding areas on the sides of the grate plates in the grate-kiln process in the hematite pellet production in LKAB, Kiruna. The steel plates are exposed to a hostile environment with heat cycles and corrosive atmosphere. An evaluation of the plates was made in co-operation with LKAB Metlab in Luleå and LKAB mechanical workshop in Kiruna. Instruments used are stereomicroscope, LOM, SEM, Spectroscope, Vickers Hardness and a surface nish meter. Results show the protruding areas of the plates are exposed to a tribochemical wear, where tops of the rough areas are torn down. A coating test is carried out at Tribolab, LTU in Luleå, using an SRV. Samples with a wear and corrosion resistant coating called Diamalloy 4276 abrade against eachother at high temperature and pressure. The coating do help to resist wear, but the environment of the test is to unrealistic to say by certain that it will help in the grate. A FEM-model in COMSOL Multiphysics 4.4 is made to calculate thermal stresses between coating and metal, the result show stresses up to 1 GPa will occur, this can be explain by the big dierence in thermal expansion coefficients of the materials. It will probably create cracks in the coating surface. Two solutions are presented, a coating is not recommended. The tribochemical wear is decreased by using a better surface nish. Therefore one can either machine the areas by drilling or milling, or one can change the casting method. Today sand casting is used, by using shell casting or precision casting, for example Shaw process, the surface nish is better over the whole plate, which also is better for corrosion resistance since less initiation points exist.Denna rapport presenterar en undersökning av slitaget på sidorna av grateplattor som används i gratekilnprocessen i hematitpelletstillverkningen på LKAB i Kiruna, även lösningar presenteras. Plattorna benner sig i en svår miljö med termiska cykler och korrosiva substanser. Utvärderingen av slitaget gjordes i samarbete med LKAB Metlab i Luleå och LKAB mekaniska verkstad i Kiruna. Utrustning som användes var Stereomikroskop, LOM, SEM, Spektroskop, Vickers hårdhetsmätare och ytnhetsmätare. Resultatet visar att sidorna av plattorna utsetts för ett tribokemiskt slitage där toppar av den grova utan slits ner. Ett ytbeläggningstest utfördes på Tribolab, LTU i Luleå, med en SRV. Prover med en beläggning har gnidits mot varandra under tryck och hög temperatur och jämförts med prover utan beläggning som utsattes för samma test. Ytbeläggningen som används står främst emot korrosion, men även slitage, den kallas Diamalloy 4276. Resultatet visar att beläggningen skyddar bra mot slitage, men miljön under testet var för orealistiskt för att med säkerhet kunna säga att det kommer hjälpa i graten. En FEM-modell gjordes med hjälp av COMSOL Multiphysics 4.4 för att beräkna de termiska spänningarna som uppstår mellan ytbeläggningen och metallen. Resultatet visar att spänningar på upp till 1 GPa kommer uppstå, detta kan förklaras med den stora skillnaden i termisk utvidgningskoecient mellan de två materialen. De höga spänningarna kan skapa sprickor i ytan. Två lösningar presenteras, en ytbeläggning rekommenderas inte i dagsläget. Det tribokemiska slitaget kan motverkas genom att förbättra ytnheten. Detta kan antingen utföras genom att bearbeta ytan, med fräsning eller slipning, eller att man byter gjutningsmetod. Idag används manuell formtillverkning, om man istället skulle använda skalformsgjutning eller precisionsgjutning, till exempel Shawprocessen, skulle man få en bättre ytnhet över hela plattan. Detta leder även till bättre korrosionsbeständighet då färre initieringspunkter nns.
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Öqvist, Mona. "Numerical simulations of wear." Licentiate thesis, Luleå tekniska universitet, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26185.
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The objective of this licentiate thesis was to study the effect of tool wear for sheet metal forming tools and how the wear process can be simulated in an efficient manner. Three Papers are appended to this licentiate thesis. Paper A covers the influence of tool geometry in deep drawing. In paper B is the way of calculating with finite element analysis described. The wear of a steel cylinder oscillating against a steel plate was studied experimentally. The worn shape of the cylinder was then compared with a numerical simulation of the shape. Paper C shows how numerical simulations can be used to simulate wear of deep drawing tools. The wear of two different deep drawing tools has been investigated. The shape of the tools before and after wear have been compared as well as the stresses and strains in the formed cups.Godkänd; 2000; 20070317 (ysko)
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Birgmark, Anja. "Wear of Coater Blades." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27183.
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Rainforth, William Mark. "Metal ceramic wear mechanisms." Thesis, University of Leeds, 1990. http://etheses.whiterose.ac.uk/4415/.
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Sliding wear of metal-on-ceramic, ceramic-on-metal, and ceramic-on-ceramic have been investigated using a tri-pin-on-disc machine. A technique has been developed for thin foil preparation for transmission electron microscopic examination perpendicular to the wear surface. The role of transformation toughening in the wear behaviour of zirconia ceramics has been investigated. In addition, the role of high strain deformation in a steel surface has been evaluated. The wear factor of 316L stainless steel pins worn against a zirconia disc was found to decrease as the load was increased, believed to be associated with metal oxide formation. TEM of the stainless steel revealed a worn surface which consisted of a mechanical mixture of metal oxide and heavily deformed metal. Deformation of the metal had occurred by shear banding with a microstructure similar to that observed in rolled specimens, although the texture formed was a wire texture rather than a rolling texture. The crystallite size was found to decrease towards the surface, demonstrating that the shear stress was a maximum at the surface. The shear bands at the surface had always been formed by the passage of the last asperity indicating that contact was plastic over the load range 6-60N/pin. The majority of wear occurred by transfer resulting from plastic overload, although a contribution to the material loss was made by metal extruded off the end of the pin as a result of the high strains. The depth of deformation correlated closely with the wear volume. The wear of the zirconia discs was found to be dominated by metal transfer. With Mg-PSZ, transformation occurred cooperatively in crystallographically determined bands. Microcrack coalescence led to preferential wear in these bands. However, with a Y-TZPdisc transformation appeared to have been responsible for widespread surface fracture. The wear of zirconia pins against a bearing steel disc gave limited metal transfer. Very little transformation of tetragonal to monoclinic was observed. However, milder forms of the transformation related wear mechanism did occur. Zirconia had formed a solid solution with the iron oxide, leading to the conclusion that the wear mechanism was tribochemically based. TZP worn against a ZTA disc showed evidence of very high temperature rises at the interface. The surface layer was amorphous and contained a mixture of alumina and zirconia suggesting that melting had occurred at the interface during sliding. At a depth of O.5pm. the surface consisted of heavily elongated tetragonal grains, with a low dislocation density, indicating a strain of at least 1.7. At a depth of 2-4pm a layer of monoclinic was found. There was evidence that the stresses imposed by friction extended to at least 8-10pm from the surface. TZP containing 20vol% SiC whiskers gave exceptionally low wear rates when worn against a ZTA disc. The greater wear resistance is believed to be a result of the improved load bearing capacity and of the higher thermal conductivity. It is clear that the poor thermal conductivity of zirconia dominates its tribological behaviour. Temperature generation was high enough to substantially reduce the driving force for transformation of the tetragonal to monoclinic, with a high enough temperature for plastic' deformation where a low thermal conductivity counterface was used. Where transformation occurred, its effect was to increase the wear rate.
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Jungedal, m. "Mild impact wear in a concrete mixer : An evaluation of wet abrasive wear." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-161557.
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The concrete mixer industry is affected by abrasive wear under both dry and wet conditions. An upgrade of the material inside the drums to high abrasion resistant steel grades can improve the lifetime and offer the possibility to reduce the weight of the drum. A new wear testing apparatus was designed to simulate the wear conditions in a concrete mixer truck with the aim to investigate the relative wear resistance for a number of steel grades. Three tests were performed under wet conditions using 16-25 mm crushed granite. The tests focused on the wear resistance under sliding and impact wear for 30 different steel grades. All of the steel grades were analyzed regarding hardness profile, microstructure and chemical composition prior to testing. Wear losses were investigated by weighing before, during and after testing. Hardness profile and SEM investigations were performed at Swerea Kimab on worn surface and cross-section after testing. Relationship between hardness and wear resistance was found over a certain hardness level. Higher hardness show better wear resistance for this type of application. The shape and degradation of abrasives were found to affect the wear rate.Betongblandare är en applikation som är utsatt för ett abrasivt slitage under både torra och våta miljöer. Genom att uppgradera materialet inuti trumman till ett slitstarkt stål kan livslängden förlängas och vikten på trumman reduceras. En ny testutrustning utformades för att simulera slitaget och miljöerna inuti en betongbil. Slitstyrkan undersöktes genom att mäta det relativa slitaget för totalt 30 stycken stålsorter. Tre stycken slitagetester genomfördes med en blandning av krossad granit, av storleken 16-25 mm, och vatten. Testerna fokuserade på att simulera både ett glidande slitage och ett lätt stötslitage. Innan testet påbörjades analyserades samtliga stålsorter med avseende på hårdhetsprofilen, mikrostrukturen och kemisk sammansättning. Materialförlusten undersöktes genom vägning före testet, under testet och efter testet. Efter testet analyserades provernas slityta i SEM och hårdheten i tvärsnittet på Swerea Kimab. Ett samband mellan hårdhet och slitstyrka kunde ses över en viss hårdhetsnivå. Testerna visade att en högre hårdhet ger en bättre slitstyrka samt att formen och nötningen av de abrasiva materialet påverkade nötningshastigheten.
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Adeva, Rodil Teresa. "Edge effect on abrasive wear mechanisms and wear resistance in WC-6wt.% Co hardmetals." Thesis, Karlstad University, Division for Engineering Sciences, Physics and Mathematics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-375.
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Wear of hardmetals is a complicated topic because the wear resistance and the wear mechanisms are influenced by microstructural factors. Although edge wear resistance has a vital importance, most of the researches made in laboratories are related to flat wear resistance using coarse abrasive paper. This situation produces problems with the prediction of abrasive wear behaviour and with the estimation of the lifetime of cutting edges of different kinds of tooling.
Several studies have been done in order to clarify edge wear behaviour. It has been published correlations of the edge toughness to the load and to the bulk fracture toughness. In those publications coarse abrasive or Vickers indenter were used.
In the present research, edge shaped specimens of WC-6wt%Co grades were investigated. In order to compare the obtained results for flat sliding and edge wear behaviour two test arrangements, pin on flat disc and edge on flat disc were employed. The specimens were tested using 120, 320, 800 and 2400 mesh SiC abrasive paper and the worn surfaces were investigated using SEM instrument to evaluate wear mechanisms. The edge wear was observed was discussed in relation to wear mechanisms investigated and correlated to the flat wear behaviour.
The obtained results showed limited applicability of the results obtained with the pin on the flat disc test arrangement for prediction of the edge wear resistance, especially in the case when size of the abrasive particles is close to the WC grain size. However, both edge and flat wear results were similar in; 1) large WC grain sized hard metals wore more than fine grain sized against coarse abrasive paper whereas the reverse occurred against fine abrasives, and 2) wear mechanisms were mainly ploughing (or grooving) for fine grain sized hardmetals in all cases, whereas wear mechanisms changed from ploughing to binder removal and carbide pull-out going from coarse to fine abrasive paper.
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SUH, Min-Soo. "Wear Mechanisms on SiC and SiC/SiC Composites under Sliding Friction and Erosive Wear." Kyoto University, 2010. http://hdl.handle.net/2433/126768.
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MacCrimmon, Donald. "Automotive brake wear debris analysis /." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1791982261&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Gåård, Anders. "Wear in sheet metal forming." Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1592.
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The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures.
Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.
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Söderberg, Anders. "Interface modeling - friction and wear." Doctoral thesis, KTH, Maskinkonstruktion (Avd.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9861.
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The general trend toward increased use of computer models and simulations during product development calls for accurate and reliable product models. The function of many products relies on contact interfaces between interacting components. Simulating the behavior of such products requires accurate models of both components and interfaces. Depending on the purpose of the simulation, interface models of different degrees of detail are needed. In simulating very large systems with many interfaces, it might be computationally expensive to integrate detailed models of each individual interface. Condensed models, or abstractions, that describe the interface properties with the fewest degrees of freedom are therefore required. This thesis deals with the modeling and simulation of mechanical interfaces in a systems context. The five appended papers discuss the issue from both the simulation and tribological points of view. The aim is to study how friction and wear can be modeled in the behavioral simulation of technical systems and to discuss the convenience and applicability of using different types of models as building blocks of a system model in simulations. Paper A reviews existing friction models of sliding contacts under different running conditions. Paper B uses a simplified contact model, the elastic foundation model, to model friction in a boundary-lubricated rolling and sliding contact. The model is integrated into a dynamic rigid body model of a mechanical system, and the system behavior is simulated. Paper C discusses the application of the elastic foundation model to rough surface contact problems and investigates how the error in its results depends on surface roughness. Papers D and E address how the wear of the contact surfaces at the pad-to-rotor interface in a passenger car disc brake can be simulated using finite element analysis (FEA).QC 20100811
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Odelros, Stina. "Tool wear in titanium machining." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-176944.
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The present work was performed at AB Sandvik Coromant as a part in improving the knowledge and understanding about wear of uncoated WC/Co cutting tools during turning of titanium alloy Ti-6Al-4V. When machining titanium alloys, or any other material, wear of the cutting tools has a huge impact on the ability to shape the material as well as the manufacturing cost of the finished product. Due to the low thermal conductivity of titanium, high cutting temperatures will occur in narrow regions near the cutting edge during machining. This will result in high reaction and diffusion rates, resulting in high cutting tool wear rates. To be able to improve titanium machining, better knowledge and understanding about wear during these tough conditions are needed. Wear tests were performed during orthogonal turning of titanium alloy and the cutting tool inserts were analysed by SEM, EDS and optical imaging in Alicona InfiniteFocus. Simulations in AdvantEdge provided calculated values for cutting temperatures, cutting forces and contact stresses for the same conditions as used during wear tests. It was found that turning titanium alloy with WC/Co cutting tools at cutting speeds 30-60 m/min causes chamfering of the cutting tool edge and adhesion of a build-up layer (BUL) of workpiece material on top of the rake face wear land. The wear rate for these low cutting speeds was found to be almost unchanging during cutting times up to 3 minutes. During cutting speeds of 90-115 m/min, crater wear was found to be the dominating wear mechanism and the wear rate was found to have a linear dependence of cutting speed. An Arrhenius-type temperature dependent wear mechanism was found for high cutting speeds, between 90 and 115 m/min.
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Kato, Hirotaka. "Sliding wear of nitrided steels." Thesis, Brunel University, 1993. http://bura.brunel.ac.uk/handle/2438/5200.
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The unlubricated sliding wear behaviour of gas nitrided, plasma nitrided, and ferritic nitrocarburized BS970,905M39 (EN41B) steels was investigated systematically from an engineering point of view. Commercial nitriding processes were employed, and the wear studies were carried out using a pin-on-disc machine over a wide range of sliding speeds and applied loads. The worn specimens and wear debris were examined by several techniques; including optical and electron microscopy and X-ray analysis. A sharp wear rate transition between mild and severe regimes was identified by varying the load for both untreated and gas nitrided steels. The wear rate was reduced by gas nitriding by up to two orders of magnitude, depending on the sliding condition. Moreover, gas nitriding expanded the mild wear region toward higher loads and sliding speeds. In the mild regime an oxidative wear mechanism operated, contrasting with the metallic wear in the severe regime. Wear maps for untreated and gas nitrided steels have been constructed, which show the dominant regimes of the wear mechanisms. A "wear-face-limited" gas nitrided pin test showed that the benefit of the treatment was lost once the effective surface layer was completely worn away. It is suggested that hardness has a crucial role in determining the wear rate through nitrided diffusion layers. A thick and porous compound layer produced by gas nitriding showed a poor wear behaviour owing to its brittleness, while a thin nitrocarburized E-Fe3N compound layer exhibited a low wear rate. There was no significant difference between the nitride steels in terms of transition load and wear rate. However, the wear lives of the nitrided layers were dependent on their case depth. Severe wear should be avoided in engineering component design, and operating conditions should ensure that only mild wear occurs. Both the hardness profiles and the cost performance of nitriding processes should be considered in the selection of nitriding treatments.
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Lingesten, Niklas. "Wear behavior of wet clutches." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18354.
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Human civilization is largely based on the transformation of stored chemical energy in the form of fossil fuels into usable work through the use of the combustion engine. In recent years, the awareness of problems such as global warming due to emissions of greenhouse gases and the depletion of fossil fuel reserves has increased. New regulations have been put into place in order to limit these effects and as a result, the efforts made by the automotive industry to limit the emissions and fuel consumption of their products has taken a higher priority. Attempting to minimize power losses is one approach taken, where the knowledge of Tribology is often made use of to lower the fuel consumption. In heavy duty equipment such as wheel loaders and articulated haulers, a large portion of the mechanical power is lost in the transmission. One of the largest contributors to the transmission power losses is the viscous drag in disengaged wet clutches. While the method of reducing these losses are quite clear (e.g. a reduction in clutch size will yield lower losses), the effects of the subsequent increase in power and energy density in clutch engagements are less clear.In this thesis, the effects of increasing the load, i.e. increasing energy input density and power absorption density, on the clutch are investigated. The main concern with increased load on the clutch is the durability of the clutch. In particular, wear of the paper-based friction material lining of the friction discs has been evaluated, as well as the influence of friction material wear on the clutch performance. A new type of test rig has been developed to quantitatively measure the clutch wear throughout a durability test. The wear measured continuously in the test rig correlates well with verification measurements performed while the engagement behavior could be clearly distinguished through the measured torque transfer.At high energy densities and high power levels, a wear phenomenon was observed where the wear rate suddenly changed. During and after the change there was no significant change in engagement characteristics. However, if a clutch which experiences two different wear rates are to be used in a transmission, it is necessary to accurately model the wear so that a compensation can be implemented in the clutch control system. The model was derived in the form of a wear equation where the clutch pack thickness is described in terms of the number of clutch engagements, employing two different wear constants. Total clutch failure due to wear occurs once most of the friction lining has been removed from the friction discs. Up to that point, the clutch is still able to deliver the required torque transfer granted that the increased distance between discs can be compensated for by smart control of the clutch. Heavy duty wet clutches need to be designed in such a way that maximum power and energy density is achieved without reaching the point where the friction lining is totally removed within the required clutch life. The use of the proposed wear model can aid in the design of new wet clutch systems to minimize the clutch's size without compromising the length of its service life.Godkänd; 2012; 20120311 (niklin); LICENTIATSEMINARIUM Ämnesområde: Maskinelement/Machine Elements Examinator: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: PhD Mikael Holgerson, SKF Industrial Division, Göteborg Tid: Fredag den 13 april 2012 kl 10.00 Plats: E246, Luleå tekniska universitet
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Jekl, John A. "Wear of thermosetting polymer bearings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0003/MQ32486.pdf.
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Kristjanson, Donna M. "I started to wear night." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0012/MQ32933.pdf.
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Yang, Jinseung. "Application of thermomechanical wear theory." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/17203.
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Paulls, Andrew. "Wear mechanisms in screw presses." Thesis, University of Hull, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395505.
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Whitehead, Alexander. "Samian: a use-wear perspective." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485393.
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The Roman conquest of Britain presages extensive changes in local material culture. This elaboration of material meant that people in Roman Britain were continually engaged in making choices and selections in material use for tasks of survival that faced them in their daily lives. Material culture is thus first and foremost something used to achieve an end, yet archaeology, normally being constrained to look at material culture in symbolic and thus semiotic terms, rarely looks at this most human and basic aspect of material culture, the way it was lived. There is thus a rupture between what archaeologists look at and the way material 'existed in the past. This study seeks to provide an alternative archaeological perspective on material culture by an investigation into slip use-wear and use-alteration on sarnian wares in Roman Britain. When a slipware ceramic is used, repeated abrasive .activity can cause the slip II to erode and the fabric underneath to become visible. To assess this process samian from a number of sites across Roman Britain was examined I and these physical i deletions were reduced to numerical information. Patterns were observed in the resulting data, and, rather being deteIlI),ined by macro-level factors such as supply, it is argued these patterns are predicated on social factors including status, activity, and culture.
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Burton, Andrew Peter. "Wear of unicompartmental knee replacements." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427771.
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Robb, Nigel Douglas. "Epidemiological studies in tooth wear." Thesis, King's College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308314.
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Watkins, Shaun Gareth. "Wear fatigue in nickel superalloys." Thesis, Swansea University, 2015. https://cronfa.swan.ac.uk/Record/cronfa43108.
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To date, work to assess the progression of wear and the effects of wear damage on low cycle fatigue has tended to be focused on specific components and their operating conditions. Although effective in the short term to solve today’s problems, these efforts often deliver insufficient understanding of the overall design space limits to have much influence of future component design. Therefore, the following research attempts to understand how wear damage progresses and how it impacts on fatigue performance in order to develop more accurate lifing models to predict the behaviour and life of real engine components. In order to do this, a survey of the internal Rolls-Royce database and public literature on wear damage on components from ex-service and current service engines was performed. Information relating to the wear scar morphologies in the reports was extracted as well as physically measuring and analysing wear damage on worn components within the Rolls- Royce failure investigation department. The wear damage was then replicated onto Udimet720Li laboratory fatigue specimens by a means of altering the pad pressure and pad sliding distance to produce a range of wear damage in order to carry out fatigue testing. Fatigue testing of the damaged specimens allowed fatigue knockdown factors to be calculated to determine the impact of wear on the fatigue life. A fretting fatigue rig was also designed and built for this research to focus on in-situ fretting fatigue at high temperatures of 600°C.
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Marcus, Kashif. "Micromechanisms of polymer sliding wear." Doctoral thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/22408.
Full textAbstract:
A study has been made concerning the tribological behaviour of ultrahigh molecular weight polyethylene (UHMWPE) during water-lubricated reciprocating sliding wear. The experimental work has been extended to study also the effect of molecular weight, fillers, lubrication, counterface roughness and sliding configuration on the polymer's transfer characteristics. The wear behaviour of polytetrafluoroethylene (PTFE) has been included for comparative studies. The worn material was studied using stylus profilometry, optical microscopy, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), Transmission electron microscopy (TEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (IR) and mass spectrometry. The effect of two fillers, namely glass beads and a titanium-based inorganic filler on the friction and wear behaviour of UHMWPE has been investigated as a function of counterface roughness (Rₐ). It was found that the filled material exhibited lower wear rates than the unfilled material on the rougher counterface. The filled material was also found to be more sensitive to a change in Rₐ and showed higher wear rates than the unfilled polymer on the smooth counterface. A uniform and coherent transfer film is found on the rougher counterface but the transfer film for the titanium-based filler was patchy on the smooth counterface. No coherent transfer film was found when sliding was conducted parallel to the grinding direction on the steel counterface, resulting in relatively high wear rates. Polymer transfer was patchy, the amount increasing as the sliding distance increased. The observed phenomena are explained in terms of mechanical interlocking and chemical bonding of the polymeric material with the metal counterface. An increase in molecular weight did not significantly improve the wear resistance of the UHMWPE. Small variations in counterface roughness values (Rₐ) were found to have a much greater effect on the wear rates than changes in molecular weight. The steady-state wear rate of the polymer was furthermore found to be more dependent on an adherent transfer film rather than a change in bulk morphology. Although PTFE exhibited low friction coefficients, the high wear rates obtained by this polymer is explained by the polymer's inability to form a transfer film under water lubrication, while any film that forms under dry sliding wear is easily peeled off the surface. Significant improvements in wear are found when fillers are added to the polymer. The wear rates for PTFE under dry sliding are similar to those obtained for UHMWPE under water lubrication. Transfet of UHMWPE material to the metal counterface during sliding wear involves interlamellar shear of the polymer and results in the development of a highly oriented transfer film. Significant differences have been found in the degree of crystallinity, crystallite size and orientation in the deformed surface layers of the polymer and debris compared with those of the bulk polymer. The worn surface of the polymer shows slightly increased crystallinity but the crystallinity of the debris is much higher than that of the bulk whilst the crystallite size is much reduced.
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Gåård, Anders. "Wear in sheet metal forming /." Karlstad : Faculty of Technology and Science, Materials Engineering, Karlstad University, 2008. http://www.diva-portal.org/kau/abstract.xsql?dbid=1592.
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Söderberg, Anders. "Interface modeling : friction and wear /." Stockholm : Maskinkonstruktion, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9861.
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MacCrimmon, Donald Cody. "Automotive Brake Wear Debris Analysis." OpenSIUC, 2009. https://opensiuc.lib.siu.edu/theses/486.
Full textAbstract:
Passenger vehicle disk brakes produce large amounts of wear debris that needs to be analyzed to verify its environmental and health impact because its effects are amplified by the massive extent of vehicular transportation around the world. An efficient and thorough method for wear debris analysis should be derived from this research to assist brake manufacturers and researchers in understanding the characteristics of wear particulates being released from current brake materials. In addition, a test method allowing inspection of brake formulations in development phase should be provided and several model "environmentally friendly" brake lining materials should be developed. The most hazardous constituents in a known brake lining formula should be replaced with non-hazardous materials that will obtain performance specifications comparable to the original formula. The brake manufacturing industry and general public should be notified of important findings from this research. Model brake linings fabricated on-site with known constituents were run through an AO4D performance dynamometer test to collect airborne and non-airborne wear debris that is comparable to wear debris produced by an average passenger vehicle. Based on previous experience with analysis of brake linings, this wear debris will be analyzed with scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX), transmission electron microscopy with EDX (TEM-EDX), X-ray diffraction (XRD), polarized light microscopy (PLM), X-ray fluorescence (XRF), and laser scattering particle size distribution analyzer (LSPSDA). Research presented in this report indicates clearly that the previous work published by several groups is lacking sufficient information and the findings should be corrected. For instance the particle size distribution detected by particle size analyzers and impactors (recommended by EPA) is not accurate and TEM as well as SEM studies allowing direct observation of wear particles revealed considerable differences between sizes detected by these analyzers and realistic particle size. EDX in combination with XRF and XRD allows for reliable identification of chemical species and crystalline phases present in wear debris. True airborne wear debris should be sampled from brake exhaust from an appropriate distance. Degummed hemp shows promising results as a copper replacement in low-metallic friction material.
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Forssblad, Matilda. "Braveheart fashion wear : Dressing titles." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-22111.
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Fashion involves more than material garments. It is extended to the settings surrounding it. We wear and dress in more than clothes, we do it in scents and lights, in objects and images. Today, when fashion mostly is consumed in pictures - a representation of the physical garment - there is a need for a shifted view of what fashion design is and potentially can become. This work aims to explore and extend the domain of fashion by using text titles as a catalyst for creative activity and seek to move beyond traditional outlets of fashion. Each title becomes a project in itself. Together they form a collection of products in the widest sense that informs the logics of my practice and pose as a suggestion for an alternative approach to collection making as well as to what contemporary fashion design can incorporate.
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Nilsson, Rickard. "On wear in rolling/sliding contacts." Doctoral thesis, KTH, Machine Design (Div.), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122.
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The aim of this thesis is to increase the understanding of wear in rolling/sliding contacts such as the wheel-rail contact for railroads and the roller-washer contact for roller bearings.
The Stockholm commuter train network has been the subject of papers A and B in this thesis in which the wear and surface cracks on rails has been observed for a period of three years. By comparing the wear depth with the crack length, equilibrium between these two damage mechanisms was found for a lubricated rail. By using a lubricant with friction modifiers the stresses was low enough to prevent crack propagation; at the same time, the rail was hard enough to reduce the wear rate. This is probably the most favourable state in terms of rail maintenance cost.
Roller bearings subjected to lubricant borne particles have been the subject of papers C, D and E in this thesis. Particles in the lubricating oil can have a significant impact on the wear in lubricated contacts. Even at low concentration levels can self-generated particles cause significant wear. The here presented results shows that filtration during run-in can significantly reduce both the mass loss and the number of self generated particles. A series of experiments has been carried out to study the wear of roller bearings by ingested lubricant borne hard particles. The form of the worn profile and the length of wear scratches correspond closely to the sliding within the contact. A count of the number of wear scratches on the rolling element surface indicates that the contact concentrates particles. A novel wear model based on the observation of a single point on the contacting surface when a concentration of particles passes through it has been developed and the necessary data for the model has been determined from the experiments. Comparison of the simulation results with the experimental results shows good qualitative agreement for the form change of the washer surfaces.
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Flodin, Anders. "Wear of spur and helical gears." Doctoral thesis, KTH, Machine Design, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2986.
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Abachi, Siamak. "Wear Analysis Of Hot Forging Dies." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605706/index.pdf.
Full textAbstract:
WEAR ANALYSIS OF HOT FORGING DIES
ABACHI, Siamak
M. S., Department of Mechanical Engineering
Supervisor: Prof. Dr. Metin AKKÖK Co-Supervisor: Prof. Dr. Mustafa lhan GÖ
KLER December 2004, 94 pages The service lives of dies in forging processes are to a large extent limited by wear, fatigue fracture and plastic deformation, etc. In hot forging processes, wear is the predominant factor in the operating lives of dies. In this study, the wear analysis of a closed die at the final stage of a hot forging process has been realized. The preform geometry of the part to be forged was measured by Coordinate Measuring Machine (CMM), and the CAD model of the die and the worn die were provided by the particular forging company. The hot forging operation was carried out at a workpiece temperature of 1100°
C and die temperature of 300°
C for a batch of 678 on a 1600-ton mechanical press. The die and the workpiece materials were AISI L6 tool steel and DIN 1.4021, respectively. The simulation of forging process for the die and the workpiece was carried out by Finite Volume Method using MSC.SuperForge. The flow of the material in the die, die filling, contact pressure distribution, sliding velocities and temperature distribution of the die have been investigated. In a single stroke, the depth of wear was evaluated using Archard&rsquo
s wear equation with a constant wear coefficient of 1¥
10-12 Pa-1 as an initial value. The depth of wear on the die surface in every step has been evaluated using the Finite Volume simulation results and then the total depth of wear was determined. To be able to compare the wear analysis results with the experimental worn die, the surface measurement of the worn die has been done on CMM. By comparing the numerical results of the die wear analysis with the worn die measurement, the dimensional wear coefficient has been evaluated for different points of the die surface and finally a value of dimensional wear coefficient is suggested. As a result, the wear coefficient was evaluated as 6.5¥
10-13 Pa-1 and considered as a good approximation to obtain the wear depth and the die life in hot forging processes under similar conditions.