Tribology of Machine Elements

Tribology is a branch of science that deals with machine elements and their friction, wear, and lubrication. Tribology of Machine Elements - Fundamentals and Applications presents the fundamentals of tribology, with chapters on its applications in engines, metal forming, seals, blasting, sintering, laser texture, biomaterials, and grinding

Plasma spray deposition of polymer coatings

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This work investigates the feasibility of the use of plasma spray deposition as a method of producing high performance polymer coatings. The work concentrates on the understanding of the processing of the plasma spraying of polymers, the behaviour of polymeric materials during deposition, and the study of process-structure-properties relationships. Processing modelling for the three stages of the evolution of a polymer deposit (droplet-splat-coating) has been carried out using heat transfer theory. A theoretical model is proposed which consists of three parts: the first part predicts the temperature profile of in-flight particles within plasma jet, the second part predicts the cooling of isolated splats impacting on a substrate and the third part, the heat transfer through the coating thickness. The heat transfer analysis predicts that the development of large temperature gradients within the particle is a general characteristics of polymers during plasma spraying. This causes difficulties for polymer particles to be effectively molten within the plasma jet without decomposition. The theoretical calculations have predicted the effect of processing parameters on the temperature, the degree of melting and decomposition of in-flight polymer particles. With the aid of the model, the conditions for the preparation of high integrity thermoplastic deposits have been established by the control of the plasma arc power, plasma spraying distance, feedstock powder injection, torch traverse speed and feedstock particle size. The optimal deposition conditions are designed to produce effective particle melting in the plasma, extensive flow on impact, and minimal thermal degradation. The experimental work on optimizing processing parameters has confirmed the theoretical predictions. Examination of polymer coating structures reveals that the major defects are unmelted particles, cracks and pores. Five major categories of pores have been classified. It also revealed a significant loss in crystallinity and the presence of a minor metastable phase in the plasma deposited polyamide coatings due to rapid solidification. The study has indicated that the molecular weight of a polymer plays an important role on the splat flow and coating structure. Under non-optimal deposition condition, substantial thermal degradation occurred for which a chain scission mechanism is proposed for plasma deposited polyamide coatings. There are difficulties in achieving cross-linking during plasma spray deposition of thermosets. The theoretical calculations predict that adequate cross-linking is unlikely in a coating deposited under normal conditions, but preheating the substrate to above the cross-linking temperature improves the degree of cross-linking of the coatings substantially. In addition, the coating thickness has a major effect on the degree of cross-linking of thermosets. The calculations also predict that lowering the thermal conductivity by applying a thermal barrier undercoat and using a faster curing agent to reduce time required for the cross-linking reaction can improve the degree of cross-linking of thermoset deposits. The experimental results for the degree of cross-linking and wear resistance confirmed these predictions.EPSRC and Mo

Environmental degradation of structural glass systems: A review of experimental research and main influencing parameters

Several factors, including incentives associated with aesthetics, transparency, high chemical, and mechanical durability, and its excellent corrosion resistance, have rapidly accelerated the interest and use of glass as windows, façades, or load-bearing elements in structural applications. Nonetheless, the glass is chemically attacked when subjected to certain environmental conditions and its chemistry, structure, as well as its optical and mechanical properties, are altered by the different weathering processes throughout its service life. Several techniques exist for evaluating the performance of weathered glass. These include both natural and artificial ageing techniques. However, little correlation has been shown to exist between natural and artificial ageing, especially the comprehensive comparison between the naturally aged and artificially weathered glazing systems have yet to be examined. In this review paper, the weathering of structural glass systems when exposed to environmental conditions is presented. Emphasis in the literature has been placed chiefly on the different types of glazing in the construction industry and their resistance to three main weathering agents: humidity, temperature, and soiling. Main optical and mechanical tests reported in the literature are summarized, and the properties described in each of them are examined, providing evidence of current challenges, limitations, and insight on future prospects

Development of a machine-tooling-process integrated approach for abrasive flow machining (AFM) of difficult-to-machine materials with application to oil and gas exploration componenets

This thesis was submitted for the degree of Doctor of Engineering and awarded by Brunel UniversityAbrasive flow machining (AFM) is a non-traditional manufacturing technology used to expose a substrate to pressurised multiphase slurry, comprised of superabrasive grit suspended in a viscous, typically polymeric carrier. Extended exposure to the slurry causes material removal, where the quantity of removal is subject to complex interactions within over 40 variables. Flow is contained within boundary walls, complex in form, causing physical phenomena to alter the behaviour of the media. In setting factors and levels prior to this research, engineers had two options; embark upon a wasteful, inefficient and poor-capability trial and error process or they could attempt to relate the findings they achieve in simple geometry to complex geometry through a series of transformations, providing information that could be applied over and over. By condensing process variables into appropriate study groups, it becomes possible to quantify output while manipulating only a handful of variables. Those that remain un-manipulated are integral to the factors identified. Through factorial and response surface methodology experiment designs, data is obtained and interrogated, before feeding into a simulated replica of a simple system. Correlation with physical phenomena is sought, to identify flow conditions that drive material removal location and magnitude. This correlation is then applied to complex geometry with relative success. It is found that prediction of viscosity through computational fluid dynamics can be used to estimate as much as 94% of the edge-rounding effect on final complex geometry. Surface finish prediction is lower (~75%), but provides significant relationship to warrant further investigation. Original contributions made in this doctoral thesis include; 1) A method of utilising computational fluid dynamics (CFD) to derive a suitable process model for the productive and reproducible control of the AFM process, including identification of core physical phenomena responsible for driving erosion, 2) Comprehensive understanding of effects of B4C-loaded polydimethylsiloxane variants used to process Ti6Al4V in the AFM process, including prediction equations containing numerically-verified second order interactions (factors for grit size, grain fraction and modifier concentration), 3) Equivalent understanding of machine factors providing energy input, studying velocity, temperature and quantity. Verified predictions are made from data collected in Ti6Al4V substrate material using response surface methodology, 4) Holistic method to translating process data in control-geometry to an arbitrary geometry for industrial gain, extending to a framework for collecting new data and integrating into current knowledge, and 5) Application of methodology using research-derived CFD, applied to complex geometry proven by measured process output. As a result of this project, four publications have been made to-date – two peer-reviewed journal papers and two peer-reviewed international conference papers. Further publications will be made from June 2014 onwards.Engineering and Physical Sciences Research Council (EPSRC) and the Technology Strategy Board (TSB

Rapid Prototyping of Microfluidic Devices:Realization of Magnetic Micropumps, Fuel Cells and Protein Preconcentrators

With the growing importance of miniaturized energy applications and the development of micro Total Analysis Systems (μTAS), we have realized microfluidic devices, namely, magnetic micropumps, microfluidic fuel cells and membrane-based protein preconcentrators, all having high application potential in future. The choice of rapid prototyping microfabrication technologies and the selection of affordable materials are important aspects, when thinking of commercialization. Thus, we have employed powder blasting, polymer molding and assembly technologies during devices fabrication throughout the thesis. The first type of microfluidic device that we present is a poly(methyl methacrylate) (PMMA) ball-valve micropump with two different designs of the electromagnetic actuator, as optimized by the finite element method. The integration of a permanent magnet in a flexible polydimethylsiloxane (PDMS) membrane, which is clamped into PMMA structure, is proposed for providing a large stroke of the pumping membrane, making the micropump bubble-tolerant and self-priming Focusing on low power consumption for μTAS integration, another type of magnetic micropump with active valves is realized. It consists of a microfluidic chamber structure in glass that is assembled with a PDMS sheet, which comprises two valving membranes and a central actuation membrane, having each an integrated permanent magnet that is peristaltically actuated by a rotating arc-shaped permanent magnets assembly. A lumped circuit model is developed to predict and describe the frequency-dependent flow rate behavior for this type of pump. Powder blasting and PDMS molding rapid prototyping technologies are employed for realization of these two types of micropumps. Fuel cells with fluid delivery and removal options, having chemical reaction sites and electrode structures that can be realized in a microfluidic format, have high potential for applications. Therefore, microfluidic direct methanol fuel cells with embedded ion- permselective medium are studied and such type of fuel cell is realized by integrating a narrow Nafion strip in a molded elastomeric structure. A mechanical clamping assembly technology enables leakage-free operation and stable performance. The characterization reveals its output power density, using H2O2-based oxidant, is among the high-performance direct methanol fuel cells in microscale. Re-using the technology of the fuel cell chip, with its particular ion-permselective Nafion membrane and assembly method, we also have developed a protein preconcentrator with high purification performance. Our device can preconcentrate negatively charged biomolecules located at the anodic compartment side of the Nafion strip within only a few minutes with a high preconcentration factor. Moreover, a complex microfluidic finite element model is proposed to study and understand the physics of the preconcentration effect. Finally, we conclude the thesis with an outlook on future developments based on our work of the project and on the assembly technologies for microfluidic device integration

The communicative theory of Terminology (CTT) applied to the development of a corpus-based specialised dictionary of the ceramics industry

Esta tesis es el resultado de un proyecto destinado a la creación de un diccionario activo, bilingüe (español-inglés; inglés-español) y especializado de la industria cerámica y azulejera con la Teoría Comunicativa de la Terminología como su pilar teórico principal. Debido al posicionamiento teórico adoptado, la investigación aquí presentada ha partido de un estudio de corpus (compilado ad hoc) en el que los términos han sido analizados in vivo y caracterizados de acuerdo al ¿habitat¿ en el que se hallan en el texto especializado. Así pues, la aproximación hecha al estudio de la terminología industrial cerámica hace pertinente el uso de la etiqueta ¿lexicografía especializada¿ a la hora de referirnos a un trabajo como éste en el que se ha tratado de ir más allá de la práctica terminográfica para dar lugar a un estudio en el que se prima el contexto, las asociaciones naturales de los términos (colocaciones) y la naturaleza comunicativa de la terminología. De este modo, en esta tesis se ha presentado de manera progresiva, además de un marco teórico detallado y coherente con el fin último de la investigación, la metodología utilizada para la elaboración del diccionario en curso, ampliamente basada en el uso de programas informáticos tanto para la explotación del corpus (WordSmith Tools 4.0), como para la creación de la base de datos terminológica (TermStar XV) y la generación de entradas finales (GENDIC).Así pues, esta tesis presenta de manera progresiva los resultados obtenidos en cada etapa del método de trabajo y 4,000 entradas finales (en este caso del inglés al español) correspondientes a las letras A, B, N, O, U y V del diccionario.This PhD dissertation is the result of an ongoing process aimed at the creation of a bilingual corpus-based specialised active dictionary of the ceramic industry, with the Communicative Theory of Terminology (CTT) as its mainstay. According to the grounding principles of the CTT, this research has departed form a corpus-based approach in which terms have been analysed in vivo and characterised from the natural habitat in which they are given in specialised communication/discourse. In this light, it has been put forward how the study of terms – made possible thanks to the activity of compiling and describing them, called terminography – may be complemented by the wider projection of specialised lexicography for the compilation and elaboration of LSP, user-oriented and user-friendly quality products in the form of dictionaries. This specialised lexicographical dimension of the work has necessarily implied the need to renew the concept of speciality language dictionaries applied to the ceramic industry and has given way to the creation of a (prospective) active dictionary in this field with a marked emphasis on context. Accordingly, the importance of pragmatic aspects in a work of this sort, has made it necessary to undertake an in-depth revision and analysis of the socio-economic context for the research in order be able to establish and solve the specific terminological needs that the ceramic industrial discourse community may find. On the basis of this theoretical framework, the method of study followed for the development of the prospective dictionary has comprised 8 broad stages: the stage of work preparation and corpus compilation, the elaboration of the field diagram, the stage of documentary corpus management, term extraction, data processing, revision and normalisation and finally, the edition stage. Two main types of results have been presented: those obtained through work in progress in the different stages of the method and final ones strictly speaking, that is, 4,000 English-Spanish entries in their final format (as they will appear in the prospective dictionary) belonging to the letters A, B, N, O, U and V of a complete dictionary which will include a total of 26,000 entries