Background. Procedural content generation (PCG) is a powerful tool used in manydifferent areas within game development. One of these areas are texturing where procedural generation have several advantages, including increased effectiveness, reducedstorage cost and unlimited texture resolution. Procedural texturing has long beenused in realistic games and the resulting textures can be indistinguishable from photographs, but when used in stylized games there is still a clear difference in aestheticbetween generated and traditionally painted textures. Objectives. By studying the visual properties of hand-painted stone tile textures,the different characteristic elements could be isolated. These elements can then beimplemented in procedural generation to recreate the iconic look. Methods. 37 different hand-painted textures were analyzed in accordance with aframework for objective art analysis used in art history. The elements identified inthe visual study were recreated in two different procedurally generated textures withthe use of Adobe Substance 3D Designer, a popular software for procedurally generating textures. Lastly a user study was conducted to investigate the impact of thedifferent elements. Results. The implementation resulted in 25 different versions which were rankedin the user study. 24 people in the ages 20-35 participated in the user study, andwhile one of the textures showed clear preference for certain elements over others,this pattern was not reflected in the second texture. Several different reasons for thisis discussed, as well as external factors that might have affected the outcome. Conclusions. The study successfully identified several elements commonly foundin hand-painted textures of stone tiles. However, the user study did not provide aclear answer to the impact of the different elements.

No description available.

MACHINABILITY ENHANCEMENT OF STAINLESS STEELS THROUGH CONTROL OF BUILT-UP EDGE FORMATION / Demand for parts made from stainless steel is rapidly increasing, especially in the oil and gas industries. Stainless steel provides a number of key advantages, such as high tensile strength, toughness, and excellent corrosion resistance. However, stainless steel cutting faces some serious difficulties. At low cutting speeds, workpiece material and the chips formed during machining tend to adhere to the cutting tool surface, forming a built-up edge (BUE). The BUE is an extremely deformed piece of material which intermittently sticks to the tool at the tool-chip interface throughout the cutting test, affecting tool life and surface integrity. Unstable BUE can cause tool failure and deterioration of the workpiece. However, stable BUE formation can protect the cutting tool from further wear, improving the productivity of stainless steel machining. This thesis presents an in-depth study of machining performance using different coated tools and various coolant conditions to examine the nature of the different tool wear mechanisms present during the turning of stainless steels. Then, different textures are generated on the tool rake face to control the stability of BUE and reduce friction during the machining process. Results show that the BUE can significantly improve the frictional conditions and workpiece surface integrity at low cutting speeds. Finally, square textures on tool rake face were found to control the stability of BUE and minimize the friction at the tool-chip interface. This reduces the average coefficient of friction by 20-24% and flank wear by 41-78% and increases surface finish by 54-68% in comparison to an untextured tool. / Thesis / Doctor of Philosophy (PhD) / Three main objectives are presented in this thesis. The first is a detailed investigation of the performance of stainless steel machining obtained by the use of different coated cutting tools and various cooling conditions. The goal of this research is to assess the reduction of tool service life, productivity, and part quality. The thesis also examines the causes of workpiece material adhesion to the cutting tool during the cutting test and to better explain its effects on tool wear and workpiece surface finish. This phenomenon is known as the "built-up edge" (BUE). Finally, different textures are applied on the cutting tool via a laser to stabilize the BUE formation on the cutting tool, thereby improving the quality of the part.

Yes / Inspired from the low wetting properties of Lotus leaves, the fabrication of dual micro/nano-scale topographies is of interest to many applications. In this research, superhydrophobic surfaces are fabricated by a process chain combining ultrashort pulsed laser texturing of steel inserts and injection moulding to produce textured polypropylene parts. This manufacturing route is very promising and could be economically viable for mass production of polymeric parts with superhydrophobic properties. However, surface damages, such as wear and abrasion phenomena, can be detrimental to the attractive wetting properties of replicated textured surfaces. Therefore, the final product lifespan is investigated by employing mechanical cleaning of textured polypropylene surfaces with multipurpose cloths following the ASTM D3450 standard. Secondly, the surface damage of replication masters after 350 injection moulding cycles with glass-fiber reinforced polypropylene, especially to intensify mould wear, was investigated. In both cases, the degradation of the dual-scale surface textures had a clear impact on surface topography of the replicas and thus on their wetting properties, too. / Europe Union H2020 research and innovation programme.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Surface texturing can be used to improve the tribological performance of mechanical contacts, in particular in the case of lubricated systems. The purpose of this work is to improve an alternative method for surface texturing based on electrochemical machining. Electrochemical dissolution combines high speed, good reproducibility and high cost-benefit ratio, which are important factors when an industrial application of surface texturing is pursued. Since the area to be textured is not required to be masked, the technique is optimized, without the need of a pre or post treatment of each surface. Another nonconventional machining technique, Electrical Discharge Machining (EDM), was used to drill microholes in the cover of the tool that will be used in the microtexturing operations. The pattern of microholes in the tool is copied onto the workpiece through the action of electrochemical dissolution. The improvement of the electrochemical texturing technique was achieved with the design of an electronic circuit with a data acquisition system and of an electrochemical cell and with the specification of the electrolyte pumping system, which improved the surface finish of the textured workpiece, as well as with the development of tools that made possible the confection of different microtexture patterns. In the electrochemical cell, the tool material was AISI 230 ferritic stainless steel and the workpiece material was carbon steel AISI 1010o. Sodium Chloride was chosen as the electrolyte tool makes the electrical contact between the electrodes. During the electrochemical texturing tests, the effect of important parameters such as the gap between electrodes, the applied voltage and the total texturing time were evaluated, and the best values found were a gap of 100 mm, a voltage between 30V and 40V and a texturing time between 20s and 60s. Different texturing patterns were obtained with good results, including dots, trace-dots and chevrons. A tribological test showed a reduction in friction and wear of a textured surface lubricated with MoS2, when compared with a smooth surface. / A texturização superficial pode ser utilizada para melhorar o desempenho tribológico de contatos mecânicos, em particular em regimes lubrificados. O presente trabalho tem o objetivo de aprimorar uma metodologia alternativa para a texturização de superfícies baseada em princípios de usinagem eletroquímica. A dissolução eletroquímica alia rapidez, reprodutibilidade e elevado custo-benefício, que são extremamente importantes quando se visa a aplicação da microtexturização em escala industrial. O não mascaramento da área a ser texturizada otimiza a técnica, dispensando um tratamento prévio e posterior de cada superfície. Uma técnica também não convencional de usinagem, a eletroerosão, foi utilizada para a microfuração da tampa da ferramenta a ser usada na microtexturização. O padrão de microfuração da ferramenta é copiado à peça pela ação da dissolução eletroquímica. O aprimoramento da técnica de texturização eletroquímica foi acompanhado pelo projeto de um circuito eletrônico com sistema de aquisição de dados, de uma célula eletroquímica e pelo dimensionamento de um sistema para bombeamento e fluxo de eletrólito, que permitiram uma melhora no acabamento superficial das peças microtexturizadas, além do desenvolvimento de ferramentas que viabilizaram a confecção de diferentes padrões de microtexturização. Na célula de texturização eletroquímica, o material da ferramenta foi o aço inoxidável ferrítico AISI 430 e o da peça foi o aço carbono 1010. O eletrólito escolhido para promover o contato elétrico entre os eletrodos foi o NaCl. Durante a texturização eletroquímica foram avaliados parâmetros importantes como o distanciamento entre eletrodos, a tensão aplicada e o tempo total de texturização, sendo que os melhores resultados foram obtidos para um distanciamento de 100 mm, uma tensão de 30 a 40 V e um tempo de texturização entre 20 e 60 s. Foram texturizados ainda padrões com formatos de ponto, traço-ponto e V , obtendo-se bons resultados. Um teste tribológico mostrou uma redução do atrito e uma diminuição do desgaste de uma superfície texturizada lubrificada com MoS2, quando comparada com uma superfície lisa. / Mestre em Engenharia Mecânica

L’appauvrissement en lubrifiant d’un contact élasto-hydrodynamique peut menacer la pérennité du film interfacial séparant les surfaces, entraîner l’augmentation des forces de frottement et l’endommagement rapide du tribosystème. Industriellement, la volonté de réduire les quantités de lubrifiant embarquées et de limiter les opérations de maintenance favorisent la sous-alimentation. L’objectif de cette thèse est de contrôler l’alimentation d’un contact EHD sous-alimenté par une texturation de surface multi-échelle, afin d’assurer une lubrification minimale à l’interface. Une démarche scientifique s’appuyant sur la dissociation des échelles spatiales, temporelles ainsi que sur l’analyse des contributions des écoulements dans les différentes zones du contact a été mise en oeuvre. La compréhension de l’interaction laser/matière en irradiation ultra-brève a permis de générer des texturations nanométriques (ripples) et micrométriques (ondulations et réseaux de cavités) à l’aide d’un laser femtoseconde. La contribution de chaque échelle topographique sur la lubrification d’un contact a été étudiée. Lorsque les forces hydrodynamiques sont faibles (contact statique), l’alimentation d’un contact résulte d’une compétition entre une contribution capillaire et une contribution visqueuse. La macro géométrie des solides déformés ainsi que la viscosité pilotent au premier ordre la propagation du lubrifiant à l’extérieur de la zone haute pression. L’imbibition de la zone de Hertz n’est possible qu’avec l’introduction d’une surface nanotexturée et sa cinétique dépend de l’orientation et de l’amplitude des ripples. Pour des nombres capillaires élevés (contact dynamique), un critère de prédiction de l’apparition de la sous-alimentation a été établi. En présence de réseaux de cavités et sous l’action d’un cisaillement interfacial, les surfaces texturées possédant une capacité de rétention élevée réalimentent la zone de haute pression. Le volume piégé envahit alors le contact puis crée une surépaisseur de lubrifiant qui protège les solides de l’endommagement tout en limitant l’augmentation du frottement. Les texturations nanométriques (ripples) et micrométriques, anisotropes et périodiques, modifient l’équilibre entre les débits de réalimentation et les débits de fuite. Une orientation adaptée des motifs peut contenir le drainage du lubrifiant dans le contact et ainsi empêcher ou retarder l’apparition d’un régime de sous-alimentation totale. Au final, chaque échelle topographique contribue à la réalimentation d’un contact sousalimenté, soit en favorisant l’expansion des réservoirs latéraux, soit en apportant localement du lubrifiant, ou en maintenant un film fluide résiduel sur les surfaces. / The lubricant depletion of an elasto-hydrodynamic contact may threaten the sustainability of the interfacial film separating the surfaces, can result in the increase of frictional forces and a rapid damage of the tribosystem. Industrially, the trend to reduce the amount of initial lubricant and to limit maintenance promotes starvation of the lubricated contact. The aim of this work is to control the lubricant feeding of a starved EHL contact by a multi-scale surface texturing, in order to ensure minimal lubrication at the interface. A scientific approach based on the separation of spatial and temporal scales, as well as the analysis of the flow contributions in different zones of the contact has been implemented.The understanding of the laser/matter interaction in ultra-short irradation has helped us to generate both nanoscale texturing (ripples) and microscale texturing such as microwaves and networks of micrometric cavities, using a femtosecond laser. The contribution of each topographic scale on the contact lubrication has been analysed. When the hydrodynamic forces are low (static contact), the feeding of the contact results from a competition between capillary and viscous contributions. The macro geometry of the deformed solids and the lubricant viscosity mainly control the lubricant spread around the high-pressure zone. The imbibition of the Hertz contact area is only possible with the introduction of a nanotextured surface. The imbibition kinetics depends on the orientation and amplitude of the ripples. For high capillary numbers (dynamic contact), a criterion has been established in order to predict the occurrence of starvation. Using a network of micro cavities and the action of an interfacial shear, the high retention capacity textured surfaces brings lubricant to the high-pressure zone. The trapped volume propagates inside the contact and creates a film thickness that protects the solids from damages while limiting the increase in friction. Anisotropic and periodic nanoscale and microscale texturing, like ripples, influences the balance between re-feeding and leakage flow rates. A suitable orientation of the geometries may prevent the lubricant from drainage and thus delay the onset of a starved lubrication regime. In conclusion, each topographic scale contributes to re-feed a starved contact, by promoting lateral reservoir extension, by providing lubricant locally where it is needed, or maintaining a residual fluid film on surfaces.

Internal combustion (IC) engines used in road transport applications employ pistons to convert gas pressure into mechanical work. Frictional losses abound within IC engines, where only 38- 51% of available fuel energy results in useful mechanical work. Piston-bore and ring-bore conjunctions are fairly equally responsible for circa 30% of all engine friction - equivalent to 1.6% of the input fuel each. Therefore, reduction in piston assembly friction would have a direct impact on specific performance and / or fuel consumption. In motorsport, power outputs and duty cycles greatly exceed road applications. Consequently, these engines have a shorter useful life and a high premium is placed on measures which would increase the output power without further reducing engine life. Reduction of friction offers such an opportunity, which may be achieved by improved tribological design in terms of reduced contact area or enhanced lubrication or both. However, the developments in the motorsport sector are typically reactive due to a lack of relative performance or an ad-hoc reliance, based upon a limited number of actual engine tests in order to determine if any improvement can be achieved as the result of some predetermined action. A representative scientific model generally does not exist and as such, investigated parameters are often driven by the supply chain with the promise of improvement. In cylinder investigations are usually limited to bore surface finish, bore and piston geometrical form, piston skirt coatings and the lubricant employed. Of these investigated areas newly emerging surface coatings are arguably seen as predominate. This thesis highlights a scientific approach which has been developed to optimise piston-bore performance. Pre-existing methods of screening and benchmarking alterations have been retained such as engine testing. However, this has been placed in the context of validation of scientifically driven development. A multi-physics numerical model is developed, which combines piston inertial dynamics, as well as thermo-structural strains within a thermoelastohydrodynamic tribological framework. Experimental tests were performed to validate the findings of numerical models. These tests include film thickness measurement and incylinder friction measurement, as well as the numerically-indicated beneficial surface modifications. Experimental testing was performed on an in-house motored engine at Capricorn Automotive, a dynamometer mounted single-cylinder 'fired' engine at Loughborough University, as well as on other engines belonging to third party clients of Capricorn. The diversity of tests was to ascertain the generic nature of any findings. The multi-physics multi-scale combined numerical-experimental investigation is the main contribution of this thesis to knowledge. One major finding of the thesis is the significant role that bulk thermo-structural deformation makes on the contact conformity of piston skirt to cylinder liner contact, thus advising piston skirt design. Another key finding is the beneficial role of textured surfaces in the retention of reservoirs of lubricant, thus reducing friction.

A thorough investigation on the existing hydrodynamic lubrication theories and the reverse pumping theories for the conventional lip seal is conducted. On that basis, the algorithms and the methods used in the numerical modeling of the conventional lip seal are modified and applied to the study of the lip seal running against surface textured shafts. For each step of the study, the numerical model is benchmarked against the experimental results. Important physical mechanisms which explain the reverse pumping ability of the triangular surface structures are revealed. Meanwhile, the accuracy of the numerical model is tested. In general, the numerical simulation results match the experimental observation well. However, there are several important discrepancies. For each discrepancy the possible causes are discussed, which benefits the further attempts of the modeling work on the lip seal running against surface textured shafts. The conclusions of this study themselves can be used as a guidance to the design of the surface textured shafts for the lip seal applications. Finally the limitation of the current theories and the modeling methods are discussed and reasonable improvements which can be done are proposed for the future work.

Les récentes séverisations des normes d’émission a indirectement conduit le groupe RENAULT à durcir et optimiser les spécifications appliquées aux surfaces en contact. Les portées de vilebrequins sont particulièrement concernées. A l’instar des développements produit/process liés au rodage des fûts de cylindre, il est envisagé depuis peu d’appliquer une texturation antifriction sur les tourillons et manetons. Ces portées de paliers sont actuellement superfinies par toilage, un procédé d’abrasion à la fois robuste et économique. Malheureusement, le toilage produit, en usine du moins, une unique morphologie de surface, à savoir, une striation circonférentielle intégrale. Il apparaît, en ce sens, très limité. La présente étude a pour objectif d’investiguer plus finement les capacités de texturation du toilage. Elle propose un ensemble d’analyses expérimentales visant à comprendre les limites texturales observées en production série et offre des solutions innovantes afin d’accroître très sensiblement le potentiel texturant du procédé. S’articulant autour du triptyque Procédé/Texture/Fonctionnalité, ce travail se positionne également dans une démarche globale en s’intéressant à la fois à la texturation laser, la caractérisation des surfaces texturées et à l’influence des textures sur la fonctionnalité statique et dynamique des paliers. Les résultats montrent en particulier que le procédé de toilage est capable de produire, de manière robuste, une véritable diversité de textures. Ils montrent également que la recherche de « poli miroir » pourraient être à prioriser sur les portées de vilebrequins. / The recent introduction of tougher emissions standards has indirectly led the RENAULT group to tighten up and optimize specifications applied to surfaces in contact. Crankshafts journals are particularly concerned. Like product/process developments linked to the honing of cylinder liners, there have been recent plans to apply anti-friction texturing to crankshaft journals and crank pins. These bearing surfaces are currently super-finished by belt-grinding, an abrasion procedure that is both robust and economical. Unfortunately, belt-grinding produces a unique surface morphology, in the factory at least, i.e. integral circumferential striation. In this sense it appears very limited. The purpose of this study is to investigate in more detail the texturing capacities of belt-grinding. It provides a set of experimental analyses aiming to understand the textural limits observed in the factory and offer innovative solutions to significantly improve the texturing potential of the procedure. Focusing on the three-pronged Process/Texture/Functionality approach, this work is also part of a global process by looking both at laser texturing, characterization of the textured surfaces and the influence of textures on the static and dynamic function of the bearings. The results show in particular that the belt-grinding procedure is capable of robustly producing a real diversity of textures. They also show that striving to achieve a « mirror-polish » finish may be something to prioritize for crankshafts journals.

A propriedade volume do fio texturizado é importante por questões estéticas e funcionais. O volume do fio pode garantir que um produto tenha bom desempenho mecânico tanto na produção dos artigos (como na tecelagem, malharia e acabamento) quanto para as aplicações finais dos produtos (produtos com alto fator de cobertura, com elasticidade, isolamento térmico etc.). A texturização por falsa torção fixada é um importante processo industrial que possui dentre os principais objetivos o aumento de volume. A etapa de fixação consiste em um tratamento térmico do fio ao final do processo, por meio da passagem do fio texturizado em um forno, conhecido como forno de fixação ou segundo forno. No presente estudo foi analisada a interação entre as variáveis temperatura do forno de fixação e sobrealimentação do fio dentro do forno de fixação. A propriedade volume dos fios texturizados é comumente tratada nas literaturas como encrespamento, termo que será utilizado no presente trabalho. Para a análise do volume do fio definiu-se três propriedades mecânicas: contração do encrespamento, módulo do encrespamento e estabilidade do encrespamento. Com a utilização da ferramenta estatística planejamento do desenvolvimento definiu-se que o estudo seria realizado com dois fatores (temperatura do forno e sobre alimentação do fio); dois diferentes níveis (mínimo e máximo para cada fator) e um ponto central. Para cada proposta de teste foram feitas 10 replicações e 50 ensaios foram realizados. Com as amostras dos fios texturizados foram realizados os ensaios para a determinação das propriedades: contração, módulo e estabilidade do encrespamento; com o equipamento Texturmat da Textechno. Com os dados, realizou-se a análise fatorial para a determinação da importância deles e a regressão linear, para a compreensão do comportamento desses dados em função dos ensaios realizados. As análises possibilitaram observar que a etapa de fixação é muito importante nas propriedades de volume do fio, sendo que a sobrealimentação do fio dentro do forno de fiação apresentou-se como a variável mais relevante para a definição desse parâmetro. / Crimp properties are important by functional and aesthetics issues. The crimp of a yarn can provide a good mechanical performance in the production (weaving, knitting and finishing) and also a good result in the final application (products with high covering factor, elasticity, thermal insulation etc). The False Twist texturing is an important industrial process that has the objective of apply bulk on the yarn. The heat setting stage consists of a thermal treatment on the yarn at the end of the process, by the passage of yarn thru a heater that is known as heat setting heater or second heater only. At this paper was analyzed the interaction between second heater temperature and yarn overfeed inside second heater. For crimp analysis were considered three mechanical properties: crimp contraction, crimp module and crimp stability. Using the statistical tool, Design of Experiments, it was defined that would be used two factors (second heater temperature and yarn overfeed inside second heater); two different levels (minimum and maximum for each factor) and a center point. For each test proposal were realized 10 replications, resulting on 50 trials. With Texturmat, from Textechno, tests were realized on the samples (textured yarn) to verify the crimp properties (contraction, modulus and stability). A factor analysis was realized with data from Texturmat to verify the importance of each factor. A linear regression for each property was calculated to better understand the data in terms of the tests. In general it was possible to see the importance of heating set stage on crimp properties of textured yarns and the yarn overfeed inside second heater is the most important variable to define this parameter.