Dissertationen zum Thema „Wear-in“

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.

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.

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.

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.

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.

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.

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.

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.

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.

The purpose of this thesis is to investigate tool wear monitoring using Fourier Series simulation of steady state cutting forces. These simulations show that mean and fundamental values are all that is required to accurately predict immersion and tool wear (high frequency terms are ignored). It is found that the ratio of the magnitude of the fundamental values of force over the quasi-mean resultant force are insensitive to wear, while the same ratio is found to change markedly with immersion. Due to the nature of wear and different cutting conditions, two different wear identification methods are proposed. The first type of wear is chipping of the primary edge; the ratio of quasi-mean resultant force over mean torque gives the necessary indication without being affected by normal wear. The second type of wear studied is the normal wear band, where the axial force, F[formula omitted], (which was modelled using equivalent chip thickness, h[formula omitted], and equivalent approach angle,[formula omitted]) is found to be useful in the identification of this type of wear. The mean value of F[formula omitted] over the mean value of torque gives information about the state of normal wear while being insensitive to chipping. Work on an insitu sensor is also reported. Preliminary investigation shows that a deposit comprising a hybrid resistor on the flank face of a throw-away insert has the potential to monitor wear due to the permanent increase in resistance of the deposit as cutting proceeds. A U.S. patent has been obtained for this idea.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

PETRÓLEO BRASILEIRO S. A.
Grande parte dos sistemas de bombeamento existentes em refinarias é do tipo centrífuga com rotor em balanço. Alguns desses sistemas, que foram fabricadas antes da década de 80, ainda estão sendo usadas em refinarias no Brasil. Tipicamente estes equipamentos possuem rotores muito flexíveis. Isto ocorre devido ao alto valor da razão entre a distância entre mancais e o diâmetro do eixo e também por causa da substituição de gaxetas, que oferecem rigidez, por selos mecânicos. Como consequência, a resposta dinâmica destes equipamentos é sensível à pequenas variações da folga entre os anéis de desgaste. O desgaste devido a erosão e ao contato entre as superfícies aumentam a folga, causando aumento da vibração e redução de eficiência, pois aumenta a vazão através dos anéis. Visando contribuir para a solução destes inconvenientes na operação de bombas centrífugas, o presente trabalho investigou a viabilidade de substituir o anel de desgaste estático por flutuante através de análise rotodinâmica com o auxílio dos softwares ROMAC e XLTRC2. A anel flutuante proporcionaria a redução da erosão e aumento da eficiência de bombeio, proporcionado pela montagem com folga reduzida. Outra vantagem é a redução da resposta ao desbalanceamento causado pelo aumento da rigidez e amortecimento. A desvantagem de usar anel flutuante é que este deve ser projetado para cada condição operacional.
A major pumping systems used in refineries is overhung centrifugal pump. Some of them, which were manufactured before 80 s, are still being used in refineries in Brazil. Usually theses equipments have flexible rotors since the ratio L/D is high and the packing, that offers stiffness, was replaced by mechanical seals in order to get more safety. As consequence, the dynamic response of these pumps is very sensitive to any variation of the wear ring clearance.Weariness due to erosion and surfaces in contact increase the diametral clearance of the wear ring, that increases the vibration and reduces the efficiency of the pump since the flow through the seals rises. So, in order to solve these two concerns (vibration and efficiency) this study investigated the feasibility of replacing the static ring by the floating wear ring through rotordynamic analyses using the following software: ROMAC and XLTRC2. Floating wear ring reduces the erosion and increases the efficiency of the pump since it permits to minimize the radial clearance. The disadvantage of using floating wear ring is that each one has to be designed for a specific operation condition.

Problem: Modeindustrin har varit omtalad under senare tid och eftersom konkurrensen på denna marknad är hög har det lett till en ökad medvetenhet bland konsumenter och speciellt bland manliga konsumenterna. En förundersökning utfärdad av författarna visade att skapandet av kundrelationer möjliggör för modeföretag att bibehålla en konkurrenskraftig position på marknaden. Undersökningen visade även att eftersom män har en tendens att förbli lojala kunder och tvivlar oftast på att köpa kläder från nya butiker är det viktigt för modeföretag att utveckla och bibehålla relationer med dessa kunder.

Syfte: Syftet med denna uppsats är att avgöra vad en relation mellan konsumenter och återförsäljare är i ett modeföretag för män och när den existerar för att kunna identifiera de viktigaste aspekterna för att utveckla och bibehålla dessa relationer.

Metod: En hermeneutik och en abduktiv ansats har använts genom hela uppsatsen medan en fallstudie har tillämpats. För att kunna uppfylla uppsatsens syfte har författarna gjort fem semi-strukturerade intervjuer. Författarna intervjuade olika chefer med olika hierarkiska positioner och butikspersonal från det valda fallföretaget.

Teorier: De teoretiska områden som har använts i denna uppsats består av teorier angående Customer Relationship Management, Fashion management, relationer mellan konsumenter och återförsäljare, konsumentbeteende, kundtillfredställelse, kommunikation i mode m.m.

Slutsatser: Författarna har fastställt att de befintliga definitionerna på relationer inte definierar vad en relation mellan konsumenter och återförsäljare är, inom det studerade sammanhanget. Därför fann författarna det lämpligt att introducera en ny definition för relationer mellan konsumenter och återförsäljare i modeföretag för män, nämligen semi-intima relationer. Dessa är långvariga relationer som karaktäriseras av ständiga personliga interaktioner, utbyte av personlig information, ett gemensamt tankesätt, tvåsidig åtagande och ömsesidiga värderingar. Författarna drog även slutsatsen att en semi-intim relation existerar när kunden är inkluderad i företaget och interaktioner är på interpersonella nivåer. En semi-intim relation existerar inte genom en handlig utan utvecklas snarare från en rad handlingar. Författarna har även fastställt att en kundfokuserad kultur, förtroende, åtagande och lojalitet, de anställdas tillfredställelse, kund tillfredställelse, värde ökande förmåner och kommunicering av varumärket till de manliga kunderna är de viktigaste aspekterna för att utveckla och bibehålla semi-intima relationer med manliga kunder. Slutligen ansåg författarna att koncepten för relationsskapande verktyg är missledande i modeföretags sammanhang och introducerade därför nya implikationer för dessa verktyg. Butikspersonalen identifierades som det viktigaste relationsskapande verktyget i modeföretag som strävar efter att utveckla och bibehålla kundrelationer.

Problem: The Fashion industry is a highly discussed issue today, and as it is very competitive, the awareness among consumers, especially male consumers, has increased. Through a preliminary research conducted by the authors, it was evident that creating customer relationships enables Fashion companies to maintain a competitive position in the market. Also, it was believed that since men tend to stay loyal and are hesitant to purchase apparel from new stores, developing and maintaining relationships with them is crucial. Purpose: The aim of this thesis is to determine what a customer-supplier relationship in Fashion companies for men’s wear is and when it exists, in order to identify the most important aspects when developing and maintaining this relationship.

Method: A hermeneutic and an abductive approach have been used throughout this thesis, while a case study was performed. In order to fulfill the purpose of this thesis, five semistructured interviews were conducted with managers, at different hierarchical levels, and salesclerks of the chosen case company.

Theories: The theoretical areas that were used in this thesis consisted of theories regarding Customer Relationship Management, Fashion management, Customer-supplier relationships, Consumer behavior, Customer satisfaction, Communication in Fashion etc.

Conclusions: The authors came to the conclusion that the existing definitions of relationships do not identify a customer-supplier relationship in Fashion retailing. Therefore, the authors found it necessary to introduce a new definition for a customer-supplier relationship in Fashion companies for men’s wear, namely semi- intimate relationships. These relationships are long-term relationships that are characterized by frequent personal interactions, personal information exchange, a shared mode of thinking, two-way commitment and mutual values beyond monetary terms. Moreover, the authors concluded that a semiintimate relationship exists when the customers are included in the company and interactions are on interpersonal levels. Furthermore, a semi-intimate relationship does not exist through one action; it is rather developed through a series of actions. The authors also determined that a customer focused culture, trust, commitment and loyalty, employee satisfaction, customer satisfaction, adding value through benefits and communicating the brand to the male customer are the most important aspects when developing and maintaining semi-intimate relationships. Finally, the authors found the concept of relational tools misleading in the context of this thesis and therefore, new implications for relational tools were introduced, with the sales force being the most important one, when developing and maintaining semi-intimate relationships.

This study focuses on the wear of piston rings in a hydraulic radial piston motor. The piston ring has to satisfy increasing demands for reliability and longer service life. It has two contacting surfaces, the face and the flank, and operates under a boundary lubrication state.

This first part of the project aimed to detect and characterise piston ring wear. Measurement by weighing gives an overall value for wear defined as loss of mass. Two-dimensional form and surface roughness measurements show the distribution of wear on the piston ring face in contact with the cylinder bore and the piston ring flank in contact with the piston groove. Three-dimensional analyses, both quantitative and qualitative, allow the wear mechanisms to be identified.

The wear of piston rings from an actual hydraulic motor was characterised. As well, rig testing was performed in two different test rig set-ups, one simulating the sliding movement of the piston ring and the other the tilting movement at the end of the strokes. Wear during the running-in period was investigated, and the findings indicate that the period when this takes place is of short duration. In the long term, mild wear makes the surfaces smoother than they were when new, resulting in a very low wear coefficient. Significant levels of wear were measured on both contacting surfaces of the piston ring. In cases in which the flank exhibits more wear than the face, the wear on the flank can be reduced by proper design of the piston groove.

The second part of the project aimed to evaluate use of a textured surface for the cylinder bore counter surface and a coated surface for the piston ring. Three modelling experiments were performed to characterise the friction and wear properties under lean boundary lubrication conditions. Under such conditions, textured surfaces have the advantage of retaining more lubricant and supplying it over a longer time. Stable friction was also a distinctive feature of the textured surface. Use of a coating could also possibly reduce the amount of wear. Though a smooth surface, like a polished one, is hard to beat for a working texture, a coated surface is far ahead of a smooth uncoated one. Different manufactured and commonly used cylinder bore surfaces, including textured ones, were evaluated in the sliding movement test rig. That allowed favourable wear properties, such as lowest wear coefficient, to be determined with the use of a roller burnished surface.

A final part of the research involved simulating wear on the piston ring face throughout the entire service life of a hydraulic motor. This allowed us to determine the roles of surface roughness and coating in prolonging service life and achieving acceptable and secure piston ring operation. The model is simple and realistic, but still needs to be refined so as to correspond even better to reality.

As abundant and widespread apex predators, elasmobranchs play influential roles in the food-web dynamics of marine communities. This has obvious implications for fisheries management and marine conservation. For successful conservation, the ecology of a species must be known. An understanding of extinct species ecology is also useful. Unfortunately, diet a key component of a species’ ecology, is relatively understudied in elasmobranchs. For a majority of elasmobranch species, little or no quantitative dietary data exists. This reflects the limitations of current dietary defining methods. This thesis presents two alternative methods that can be used to determine the diet of extinct and extant elasmobranchs: meso-style wear analysis and 3D tooth microtextural analysis. These wear techniques can be applied to small sample sizes, and sampled animals with no stomach contents, thus reducing the impact of study on wild elasmobranch populations. The techniques can also be applied to dried and fossil samples, further reducing the impact of study on wild populations and providing a means for the study of extinct species. Furthermore, these wear techniques provide additional advantages over the traditional methods of stomach contents analysis and observation. The wear, measured through the methods outlined in this thesis, accumulates over a longer timescale. The “snapshot bias” associated with traditional methods is thus overcome when analysing diet via meso-style analyses or 3D microtextural analyses. This thesis also investigates the impact of sediment abrasion to 3D tooth microtextures. Results show that care needs to be taken when comparing fossil specimens originating from deposits with differing sediment compositions. These findings are applicable to any study using 3D microtextural techniques on fossil specimens of any species, as all have been exposed to sediment abrasion before fossilisation. This is the first time that these alternative wear methods have been applied to elasmobranchs. They have displayed the potential to be a powerful tool for the dietary analysis of living and extinct elasmobranchs in the future.

Bibliography: pages 133-136.
A survey has been made of the quality and type of materials used for tillage tools in South Africa. Conclusions have been drawn regarding the inadequacy of the manufacturing processes used and the resultant quality of the tool material. A rig has been designed for the abrasion testing of materials in soil. The reproducibility of the method has been shown to be high and an evaluation has been made of the relative wear resistance of a series of ·heat treated steels. A medium carbon boron steel has been shown to have great promise as a tillage tool material because of its high wear resistance and toughness. The deformed surface layers and the mechanisms of wear of steels subjected to field and laboratory abrasive testing has been examined. The removal of material through predominantly ploughing or cutting mechanisms has been shown to be dependent on the heat treatment and composition of the steels together with the nature of the abrasive. White surface layers have been observed to form on medium and high carbon steels subjected to soil abrasion. Suggestions have been advanced for their formation. Attempts have been made to assess the transferability of data between field and laboratory testing.

Wear transitions in the wheel–rail contact are of increasing interest since the general trend in railway traffic is toward increased velocities and axle loads. Curving increases the risk of flanging, causing the contact to change from an almost pure rolling wheel tread–rail head contact to more of a sliding wheel flange–rail gauge contact on the high rail in curves. Under wheel flange–rail gauge contact conditions, wear transitions to severe or catastrophic wear will occur if the contact is improperly lubricated. Such a transition is the most undesirable transition in the wheel–rail contact, as it represents a very expensive operating condition for railway companies. The contact conditions responsible for this transition are very severe as regards sliding velocity and contact pressure, and thus place high demands on both the lubricant and the wheel and rail materials. The focus of this thesis is on the transitions between different wear regimes in a wheel–rail contact. Wear is discussed both in traditional tribological terms and in terms of the categories used in the railway business, namely mild, severe and catastrophic wear. Most of the work was experimental and was performed at the Royal Institute of Technology (KTH), Department of Machine Design. The effects of contact pressure, sliding velocity, and type of lubricant have been investigated, producing results that resemble those of other studies presented in the literature. The absence of research relating to the wheel flange–rail gauge contact is addressed, and it is concluded that a lubricant film must be present on rails in curves to prevent severe or catastrophic wear. The formulation of this lubricant can further increase its wear- and seizure-preventing properties. To obtain a deeper understanding of wear transitions, methods such as airborne particle measurement and electron microscopy have been used. Paper A presents the test methodology used to detect seizure and discusses the wear-reducing influence of free carbon in highly loaded contacts. Paper B presents the testing of seizure-initiating conditions for a range of environmentally adapted lubricants applied to wheel and rail materials; a transient pin-on-disc test methodology was used for the testing. Paper C presents the use of pin-on-disc methodology to study the wear-reducing effects of a wide range of lubricants. The best performing lubricant was a mineral oil containing EP and AW additives. Paper D relates wear rates and transitions to airborne particles generated by an experimentally simulated wheel–rail contact. The airborne particles generated varied in size distribution and amount with wear rate and mechanism. Paper E relates additional analysis techniques, such as FIB sectioning, ESCA analysis, airborne particle measurements, and SEM imaging of airborne wear particles, to the contact temperature.
QC 20100721
Samba 6

In several large cities in Norway the traffic volume is high. The use of studded tires and other friction enhancing measures during winter leads to significant pavement wear, which in turn leads to an increase in the amount of airborne particulate matter, often exceeding the limits set in the ambient air regulation. This represents a nuisance or health risk for people being exposed to the pollution. According to regulations set by the European Union particulate matter is measured and regulated through mass concentration of particles less than 10 μm in diameter (PM10). However, studies of health effects related to exposure to particulate matter have shown that particle properties like morphology and composition are essential regarding toxicity and in considering risk of developing disease. There seems to be a more complex relationship between dust pollution and health effects, which cannot be explained with just the mass concentration alone. This makes it necessary to characterize the physical and chemical properties of the road dust. Characterization of road dust particles is important to provide basis for a better understanding of the pavement wear and production of road dust and its influence on human health in urban areas. The overall purpose of this study has been to characterize particles generated from pavement wear qualitatively and quantitatively.

Five papers are included in the thesis. Paper I and II present field investigations of road dust sampled in the vertical direction close to an urban road in Trondheim, Norway. In Paper III different laboratory methods have been used for simulation of pavement wear and road dust generation by studded tires. Paper IV and V describe how aggregate size, driving speeds and vehicle tires affect pavement wear and particle properties.

The main conclusions from the study are:

Studded tires used in the winter season in Norway are the main cause for generation of road dust from pavement wear. If studded tires were not used, there would be much less suspended particulate matter originating from wear of pavements in urban air. Studded tires produce much more dust particles from wear of pavements compared to nonstudded tires. For instance, at 60 km/h studded tires produce 30-40 times more TSP compared to non-studded tires on an SMA 8 pavement measured in an indoor test facility. The airborne road dust is composed of almost 90 % by weight of mineral particles under winter conditions, and approximately 50 % of the particles have size smaller than 25 μm (D50). Based on all samples analyzed, D10 is 3 μm and D90 is 60 μm. However, agglomeration of particles seems to make the measured particle size distribution coarser than it really is. Studded tires generate dust with finer particle size distribution than non-studded tires. The main fraction of the particles can be described as rounded particles, with average roundness value around 0.6. The specific surface area of the sample is dependent on the amount of organic material present in the sample and the particle size distribution. In general, field samples have higher specific surface area than dust particles generated in laboratory because of higher organic content. However, finely ground particles produced in laboratory may exhibit even higher surface area than field samples of road dust because of finer particle size distribution. Surface area is an important factor in health considerations since the reactivity of particles increase with increasing surface area.

Other factors affecting the generation of particles from pavement wear are the driving speed and type of rock material used in the pavement. Test results show that the PM10 concentration measured under laboratory conditions is reduced by 32-49 % when reducing the driving speed from 70 to 50 km/h, 52-83 % when reducing the driving speed from 50 to 30 km/h, and 76-89 % when reducing the driving speed from 70 to 30 km/h. The driving speed affects the particle size and the particle shape distributions. Increasing driving speed generate particles with finer particle size distribution and more irregular particles. The rock material used in the pavement affect the amount of dust generated, the composition, the particle size distribution, the shape distribution, and the specific surface area. Some mineral types are regarded harmful to health, for example quartz and asbestos which are classified as carcinogenic. The total amount of airborne dust (TSP) and PM10 can be very different; a high TSP does not necessarily lead to a high PM10 concentration and vice versa.

This study has shown that it is possible to produce dust comparable to studded tire wear by use of simple laboratory techniques. This has significance with regard to cost because it is not necessary to build expensive test sections when the purpose is to generate and characterize the dust from pavement wear. The small scale asphalt testing procedures, Prall and Tröger, are the methods best suited to give fine material which is comparable to particles generated from the Pavement testing machine (PTM). It also seems that one can test the aggregate alone to get reasonably good samples for analysis of dust from wear by studded tires. Among the aggregate testing procedures, the Los Angeles (LA) method gives the best correlation with the PTM. The dust produced by Tröger and Prall is more similar to the dust produced in the field because the dust is generated from asphalt mixtures, while the dust produced by LA, Nordic ball mill (KM) and micro-Deval (MD) comes from the aggregate only. However, none of these methods include/simulate the effect of the car tire, only the studs.

The results have shown that apart from the use of studded tires, the rock material used in the pavement has a significant influence on the airborne dust generated. It is therefore important to carefully select the rock materials for use in urban road pavements. The aggregate type affects both the amount of dust generated and the particle properties. Existing knowledge shows that the finer the particles, the greater will be their potential effects on health. Since driving speed influences both the amounts of road dust generated and the particle size distribution, one may have to consider the use of speed restrictions in urban areas in winter time to reduce the potentially hazardous effects of road dust. However, this has to be balanced against other traffic conditions such as congestion.

Thesis (MScEng)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Fretting wear results in the loss of fit and tolerance at contact interfaces. The aerospace and aircraft industry is severely impacted by fretting wear and fretting fatigue that frequently occurs in turbo machinery and riveted structural connections. There have been numerous studies, investigating the fretting phenomenon for these aerospace applications. Literature available in regard to fretting wear encountered in these aerospace applications is limited. This study is therefore aimed at investigating the fretting wear encountered in aerospace application. An in-house fretting test apparatus was specially designed and developed in order to perform the fretting wear experiments. Ti-6Al-4V and Al7075-T6 are the two aerospace materials that were tested using the fretting test apparatus. An extensive experimental study was conducted in order to investigate the effect of the normal force on the fretting wear and friction behaviour of the two aerospace materials. The most severe of these experiments were identified and then repeated for up to 106 fretting cycles. Additional fretting wear experiments were also conducted between the two aerospace materials and cemented carbides, since the carbides are currently being utilized as coatings in some aerospace contacts that are prone to fretting induced damage. The experimental study revealed that a decrease in the normal force resulted in an increase in the severity of the fretting wear of both aerospace materials. The additional fretting wear experiments involving carbide-metal contact couples found that Ti-6Al-4V and Al7075-T6 were prone to adhesive wear.
AFRIKAANSE OPSOMMING: Knaagslytasie veroorsaak materiaalverlies by die kontakoppervlakke. Die lugvaart industrie is erg geraak deur knaagslytasie en knaaguitputting wat dikwels voorkom in turbo-enjin toepassings en strukturele verbindings. Daar was al talle studies gedoen oor die effek van knaag op lugvaart toepassings. Literatuur met betrekking tot knaagslytasie in lugvaart toepassings is egter beperk. Hierdie studie was dus gemik daarop om knaagslytasie in sekere lugvaart toepassings te ondersoek. Tydens die studie is ʼn toetsopstelling ontwerp en ontwikkel om knaagslytasie eksperimente uit te voer. Ti-6Al-4V en Al7075-T6 is die twee lugvaartmateriale wat ondersoek is met behulp van die toetsopstelling. ʼn Omvattende eksperimentele studie is gedoen om die effek van die normaal krag op knaagslytasie en die wrywings gedrag van die lugvaartmateriale te ondersoek. Die eksperimente wat die ergste slytasie en hoogste wrywing getoon het, is herhaal vir 106 siklusse. Bykomende knaag eksperimente was ook tussen die twee lugvaartmateriale en sekere karbiede gedoen, aangesien karbiede tans as deklae in sommige lugvaart kontakte gebruik word. Die eksperimentele studie het getoon dat 'n afname in die normale krag gelei het tot 'n toename in wrywing vir beide lugvaartmateriale. Die bykomende knaagslytasie eksperimente op karbied metaal pare het getoon dat Ti-6Al-4V en Al7075-T6twee lugvaart materiale nie in staat was om enige van die karbide te beskadig nie. Die lug-en Ruimte-materiaal aan die ander kant ervaar het kwaadaardige dra.

The ‘Dynarat’ computer simulation of ratcheting wear and failure of rail steel has been developed at Newcastle University over the past decade based on laboratory tests and analysis of British normal grade (R220) rail steel. The aim of this thesis is to develop material models for Dynarat that can be used to predict wear and rail life for R260 rail steel, which is used widely in Europe and increasingly in Britain, and also for newer premium grade pearlitic rail steels. Laboratory twin-disc testing and metallurgical material analysis were used to obtain data for characterising and modelling material response to repeated loading. The relationship between material hardness and plastic shear strain is central to the material model used in the Dynarat simulation, and is determined for the materials tested here by studying the measured hardness and plastic strain. Additional calibration of the wear rate was achieved by performing Dynarat simulations that closely matched the laboratory tests. In addition to the material model development, the contact stress model used by Dynarat for modelling wheel-rail contact is improved. Previously the driving stress for plastic strain accumulation was the orthogonal shear stress in the plane of the simulation. In the new model, plastic strain accumulation is now made directional, with components in the x and y directions. Partial slip is now implemented in the 3D simulation, to approximate the real wheel-rail contact, with both contact region and adhesive zone modelled as ellipses. Two types of high-speed train at two curves on the UK’s East Coast Main Line have been simulated with the new computer model to study the effects of traffic mixtures. Wear rates and time until crack initiation are obtained. The new model provides a tool to help rail/wheel manufacturers to choose the best steel, and for maintenance personnel to predict rail wear and cracks, and thus to help plan grinding schedules in order to optimise rail life and safety.

This dissertation investigates the friction and wear behaviour of the predominant materials used in lower limb prostheses. plastic debris is common as a result of articulation at heavily loaded joint surfaces but metal debris can also be generated at the soft-tissue interface where the contact forees are much lower. The resultant tissue staining, and the wear products in general, are a matter of great concern: the plastic particles migrate between the bone-implant interface and have been implicated in the process of bone resorption with subsequent loosening of the implant and there is some evidence that release of corrosion and wear particles from permanent metal prostheses could constitute a carcinogenic hazard. The hypothesis for the phenomenon of soft-tissue wear of the body of massive prostheses was that there were particular combinations of physical contact conditions which led to high metal wear rates. Part of the experimental programme was an attempt to reproduce this wear phenomenon in the laboratory and to determine the conditions which influence soft-tissue wear. The conditions governing the wear of titanium by soft-tissue have not hitherto been investigated. The findings from the investigation were surprising and non intuitive in that metal was severely damaged by soft-tissue attrition. The findings contribute to the understanding of the causes of this type of wear. There is evidence that the hypothesis suggesting low contact loads create higher coefficients of dynamic friction, and subsequent wear, than that occurring with high contact loads was demonstrated and explained by reference to the phenomenon of a stick-slip mechanism. This would offer an explanation of why the explanted prostheses of elderly, low body weight patients, with reduced activity levels, often exhibit more severe wear from the shaft of prostheses than younger, heavier, and more active patients. The experimental findings could also help explain the reasons for patients with apparently similar sets ofin vivo biochemical conditions exhibiting extreme differences in debris production and tissue staining. Laboratory studies have also been carried out which investigate some of the predominant parameters which influence wear in prostheses such as material quality, conformity, thickness, temperature distribution, and the relative effects of sliding and twisting in the knee. The objective here was to effectively simulate the wear observed on retrieved plastic tibial components. Emphasis has been given to the development of wear test methodology and strict protocols for in vitro testing have been proposed and employed in an attempt to identify the causes of wear and aetiology of failure. Pin-on-disc, pin¬on-plate, and simulators have been used to reproduce the conditions associated with knee joint replacements. The experimental work examines the factors that cause damage and evaluates the relative merits of various materials, surface coatings, and surface treatments which could be used to reduce surface degradation and wear of prostheses at both the articulating surface and at the soft-tissue interface. The precise wear rate of titanium by soft-tissue has been determined and the work offers an increased understanding of this wear phenomenon. Minimising the rate of production of debris will reduce adverse cellular response and the potential revision of the implant. The investigation demonstrated that inherent defects in polyethylene lead to enhanced wear and quantifies the benefit offered by treatments to both plastic and metal components for in vivo applications. It is recommended that the metal faee of the femorotibial joint is nitrogen ion-implanted and that the titanium shaft of massive endoprostheses are diamond-like carbon coated. This research results in a better understanding of some of the significant causes and mechanisms of wear in lower limb endoprostheses and offers some proposals for reducing this wear.

Objective: The purpose of this study was to develop a method of accurately quantifying the wear facet, and relating the wear facet size to the forces applied by the Iowa Tooth Wear Machine. Methods: Ten un-erupted third molars were used for this study. The teeth were mounted in the Iowa Tooth Wear Machine with opposing proximal surfaces. Samples were run with a 0.250mm stroke length for 645,120 cycles under 5 pounds of weight. An optical scanner was used to digitize the initial and final interproximal wear facets. AnSur© software (Regents, University of Minnesota) was used to process and analyze the interproximal surfaces in terms of area (mm2), volume (mm³), and depth (µm). Results: All samples were subject to identical magnitude and frequency of forces. The results show that there was considerable variation in volume loss between the samples. Results show similar amounts of volume loss in samples 3, 4, 6, 7, 8, 9, and 10 with 1, 2, and 5 showing a considerably greater amount of wear. Conclusions: The results suggest that there may be other compounding factors involved with facet formation, and the force magnitude and frequency alone does not determine the volume of enamel loss.

The purpose of this pilot study was to develop a method to quantify the surface area of interproximal wear facets present in the human dentition. Another aim was to investigate the reliability of this method and possible correlations between the amount of interproximal tooth wear and vertical craniofacial morphology. The study was carried out on 24 adolescent individuals immediately prior to orthodontic treatment. Following interproximal contact separation of one week, interproximal impressions were taken with polyvinyl siloxane and a positive stone model was fabricated with type IV dental stone. The model of the wear facet was imaged using a computer-operated optical scanner and the border of the wear facet was digitally traced. From the digital tracing, the surface area of the wear facet was calculated. The intra-observer reliability of this method showed a strong agreement in repeated measurements, however the inter-observer reliability revealed some statistically significant differences between two examiners. The limited sample size could not reveal a significant relationship between interproximal tooth wear and vertical craniofacial morphology. This study serves as a proof of concept study from which further in vitro and in vivo research can be conducted to better understand the relationship between masticatory input (as measured by interproximal wear) and craniofacial morphology.

Bibliography: leaves 60-68.
The hydraulic transportation of particulate solids through pipelines results in wear of the pipeline walls. The lifetime of the pipeline is determined by this rate of material loss and is therefore critical to the designer. Due to the small amounts of material lost in in-situ tests, requiring in many cases in excess of 1000 hours testing, an accelerated test procedure is necessary. This work introduces an accelerated method of evaluating materials under simulated pipeline wear conditions. The solids in the slurry and the materials were closely monitored to attain an understanding of their interaction. The wear rate of the materials tested was found to decrease with a decrease in the average rounding of the particles. These changes in particle characteristics occur with time due to comminution within the pump and pipeline. The mechanical properties and wear rates of the materials evaluated were examined to determine whether any relationships existed.

Includes bibliographical references.
The abrasive nature of fly ash handled in large coal-fired power stations results in unacceptable material and maintenance costs in ash-water mixing plant. Wear testing has been carried out in situ using a variety of generic materials. A ranking order of wear performance has been established both as a function of material and operating costs, and it has been demonstrated that impressive cost savings can be effected by the use of ceramic-coated steel mixing blades. The performance of such composites has been found to be sensitive to the design and method of application. To optimise materials selection, a family of tungsten carbide-cobalt cermets together with a number of structural ceramics were tested in situ. The modes of wear can be related to material constitution. By ranking the performance of these candidate materials, value based materials selection and design for use can be applied.

A vertical pin on horizontal disc machine has been used to conduct a series of experiments in air under dry and lubricating sliding conditions. For dry sliding low load and speed combinations were chosen to correspond to the mild wear region below the Welsh T1 transition. Lubricated tests were conducted under flooded conditions using Esso Technical White Oil alone and with a 0.1% stearic acid additive, for load and speed ranges that produced substantial amounts of asperity contact and thus a boundary lubricated regime of wear. The test material in all cases was AISI 52100 steel, for unlubricated sliding subjected to loads from 5 to 50 N and a range of speeds from 10-3 to 1.0 ms-1, and for lubricated sliding loads of 50 to 123 N and for speeds of 10-2 to 1.0 ms-1. Unlubricated wear debris was found to be a mixture of -Fe_2O_3 and -Fe. Unlubricated wear was found to occur via a thin film logarithmic oxide growth followed by agglomeration into thicker oxide plateaux 2 to 10 m in thickness. Lubricated wear occurred via thick film diffusion controlled oxide growth producing homogeneous oxide plateaux 0.1 to 0.2 m in thickness. X-ray photoelectron spectroscopy identified the presence of a surface film on pins worn in White Oil with stearic acid, which is thought to be iron stearate. A model has been developed for unlubricated wear based upon the postulated growth of thin film oxides by a logarithmic rate law. The importance of sliding geometry and environment to the dominant wear mechanism has been illustrated.

In the automotive industry, press hardening is usually employed to produce safety orstructural components from advanced high–strength steels. This hot forming process, andthermomechanical forming processes in general, is highly dependent on friction betweentool and workpiece as friction affects and controls the deformation of the workpiece.However, friction is also directly associated with wear of the forming tools. Tool wear isa complex system response depending on contact conditions and is a serious issue whenit comes to process economy as it reduces the service life of the tool. Therefore, it isnecessary to enhance the durability of thermomechanical forming tools by studying theinfluence of parameters such as contact pressure, cyclic thermal loading, repetitive mech-anical loading and others on tool wear. Then, computational mechanics can be utilised tonumerically simulate and optimise the thermomechanical forming process by predictingwear of the tools.Dry sliding tests were carried out on a high temperature reciprocating friction andwear tester. The aim was to identify the occurring wear mechanisms and determine thetribological behaviour of prehardened hot work tool steel when sliding against 22MnB5boron steel. A normal load of 31 N, which corresponds to a contact pressure of 10 MPa, asliding speed of 0.2 ms −1 and temperatures ranging from 40◦Cto800◦ C were employed.It was found that the coefficient of friction and the specific wear rate decreased at elevatedtemperature because of the formation of compacted wear debris layers on the interactingsurfaces.Increasing material and energy expenses, rising demands for process flexibility andstability as well as requirements for minimal trial and error have led to a growing interestin numerical simulation of wear phenomena. Finite element simulations of a strip drawingtest were conducted to explore the possibility of predicting tool wear in press hardening.The focus laid on unveiling the contact conditions on the forming tools through numericalsimulation. The influence of high temperature on wear was studied and the results wereimplemented in Archard’s wear model to introduce temperature dependence. Further-more, another wear model used for warm forging was also considered. It was found thatthe extreme contact conditions occurred at tool radii and that the different wear modelsled to similar wear depth profiles on the radii but with different orders of magnitude.Standard high temperature tribometers allow fundamental tribological studies to becarried out in order to investigate the tribological behaviour of the materials in contact.However, the conditions prevalent during the interaction of the hot workpiece and toolsurfaces in thermomechanical forming are not adequately simulated in these tribometers.A novel high temperature tribometer has been employed in order to more closely simulatethe interaction between tool and workpiece at elevated temperatures during thermomech-anical forming. It was found that a higher load led to a lower and more stable coefficient
Godkänd; 2014; 20140919 (sermoz); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Sergej Mozgovoy Ämne: Maskinelement/Machine Elements Uppsats: High Temperature Friction and Wear in Press Hardening Examinator: Professor Braham Prakash, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Dr Manel Rodriguez Ripoll, AC2T research GmbH, Österrike Tid: Fredag den 21 november 2014 kl 10:00 Plats: E231, Luleå tekniska universitet

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics
This work project aims to: 1) Explore weather men in Portugal will wear make up in the future; 2) Analyze changes in male grooming from the beginning of the 1900´s until the present time. 3) Analyze how cosmetic brands are branding to men. In order to be able to answer the questions above, secondary data was collected in the form of consumer studies and research, newspaper articles and other literary material. Since this market is still in a developing stage. It was very difficult to obtain academic papers on the subject of male make up. Then, in order to obtain primary data, it was therefore essential to conduct exploratory research. This research is the essence of the work project as it enabled me to have a privileged and detailed outlook on male attitudes towards make-up and grooming products in general, regarding the Portuguese market. In order to do this, I carried out in depth interviews as part of my exploratory research and concluded that although men in Portugal have gone a long way in the grooming process, especially in the last few years they are still very negative towards the idea of wearing make-up. Considering this, cosmetic companies should therefore be alert to this potential market and analyze it thoroughly before introducing male make-up products in the Portuguese market.