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Orrling, Diana. "Towards Abatement of Selected Emissions from Metals Manufacturing". Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26107.
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Although the metallurgical industry has made great strides in the reduction of unwanted emissions to the atmosphere as a result of production processes, significant challenges still exist. From a global perspective, even large reductions in emissions per produced ton become immaterial when considering that the total world production of metals continues to increase. Two such particularly hazardous emissions are sulfur dioxide, primarily from copper ore roasting, and mercury, which has had increasing emissions from the steel industry in recent years. Both pollutants have severe consequences for the environment and also for human health. The primary motivations of this work have hence been: (1). to study sulfate formation on soot from sulfur dioxide emissions reacting with ozone and H2O in the vapor phase and (2). to study factors involving the behavior of mercury adsorption on metal surfaces involved in steelmaking, in order to further the understanding of select emissions from scrap-based steelmaking. Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on soot in the presence of ozone and water vapor. The sulfur dioxide oxidation into sulfate was quantified using a particle-into-liquid sampler coupled with ion chromatography to measure the sulfate formation at atmospheric pressure. Water vapor, ozone and sulfur dioxide concentrations were controlled. Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites were observed. The exposure also caused the soot to become hydrophilic, due to the sulfur dioxide adsorption and also likely the formation of carboxyl groups on the surface. No significant increase in sulfate formation was observed at ozone concentrations above 1000 ppm. The effects of common surface contaminants such as oxygen and chlorine were examined on the metal surfaces, as well as the impact of changes in temperature, with controlled conditions using thermal desorption auger electron spectroscopy. It was established that low temperatures (82 K through 111 K) were conducive to mercury adsorption, wherein physisorption and subsequent lateral mercury interactions in mercury adlayers occurred. Chlorine appeared to favor mercury uptake, as determined by the increased mercury coverage at low temperatures on polycrystalline iron, copper and zinc. Oxygen, however, was found to be an inhibitor of mercury, most notably at room temperature. It was surprising to establish that no mercury adsorbed on zinc surfaces at room temperature and only on polycrystalline samples at low temperature. The mercury signal intensity increased up to the limit of the melting temperature for iron systems, on the oxidized copper surface and the polycrystalline zinc surfaces, prior to desorption from the surfaces. It is suggested that this is due to a rearrangement of mercury atoms on the surface at increasing temperatures, whereas at 85 K, mercury adhered to its initial adsorption position. In other words, mercury wet these surfaces on annealing, transitioning from an islanded surface at low temperature to a smooth layer before desorption. Based on these results, it was concluded that the mercury bond to the oxidized surface was weakened compared to clean copper. Furthermore, it is proposed that a surface phase transition occurred on polycrystalline zinc prior to desorption. No such transition was observed on iron. Activation energies of desorption were calculated for the relevant metal surfaces. It was established that clean iron had the highest activation energy of desorption. The large bond strength between mercury and iron may account for the highest desorption temperature of the iron systems. Zinc and copper had similar activation energies and desorption temperatures, which were respectively lower than that of iron. X-Ray Photoelectron and Auger Electron Spectroscopy were used to ascertain common surface contamination, i.e. chlorine, oxygen and sulfur, which affected mercury adsorption. Laser Ablation Inductively Coupled Plasma Time of Flight Mass Spectrometry was used to determine the depth of mercury adsorption on the samples. The technique also showed that the samples contained mercury in the surface layers. Accompanied by the rising demand for metals is the increase in emissions from metals manufacturing. Moreover, it is critical to minimize sulfur dioxide emissions as particulates from soot continue to be released in the atmosphere. For scrap-based steelmaking, monolayer mercury adsorption on clean iron and copper at room temperature are significant results. With the rising use of electronic devices in vehicles, the sorting of scrap becomes increasingly important. Mercury not adsorbing on zinc at room temperature is also of relevance as it disproves the theory of increased mercury adsorption with the increased use of galvanized scrap in summer conditions. However, the low temperature studies showed multilayer adsorption of mercury on iron, zinc and copper, which has relevance for the reported temporal variations of mercury deposition in arctic regions. Keywords: mercury, iron, zinc, sulfur dioxide, adsorption, pollution, thermal desorption, polycrystalline, surfaces, spectroscopyQC 20120326
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Voisey, Kathleen Theresa O'Sullivan. "Laser drilling of metals and ceramics". Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272329.
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Fan, Zongyue. "A Lagrangian Meshfree Simulation Framework for Additive Manufacturing of Metals". Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1619737226226133.
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Shen, Ninggang. "Microstructure prediction of severe plastic deformation manufacturing processes for metals". Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6282.
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The objective of the research presented in this thesis has been to develop a physics-based dislocation density-based numerical framework to simulate microstructure evolution in severe plastic deformation (SPD) manufacturing processes for different materials. Different mechanisms of microstructure evolution in SPD manufacturing processes were investigated and summarized for different materials under dynamic or high strain rates over a wide temperature range. Thorough literature reviews were performed to clarify discrepancies of the mechanism responsible for the formation of nanocrystalline structure in the machined surface layer under both low-temperature and high-temperature conditions.
Under this framework, metallo-thermo-mechanically (MTM) coupled finite element (FE) models were developed to predict the microstructure evolution during different SPD manufacturing processes. Different material flow stress responses were modeled subject to responsible plastic deformation mechanisms. These MTM coupled FE models successfully captured the microstructure evolution process for various materials subjected to multiple mechanisms.
Cellular automaton models were developed for SPD manufacturing processes under intermediate to high strain rates for the first time to simulate the microstructure evolution subjected to discontinuous dynamic recrystallization and thermally driven grain growth. The cellular automaton simulations revealed that the recrystallization process usually cannot be completed by the end of the plastic deformation under intermediate to high strain rates. The completion of the recrystallization process during the cooling stage after the plastic deformation process was modeled for the first time for SPD manufacturing processes at elevated temperatures.
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Holt, Linda Ann. "A Cross-Regional Comparison of Fabricated Metals' Manufacturing Sector Resiliency". ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/1704.
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Fabricated metals' manufacturing sector employment in the United States declined following the onset of the 2008 recession. Premium compensation and benefits afforded to employees within the manufacturing sector amplified the negative effects of recessionary job losses. Using the regional macroeconomic complex adaptive systems (CAS) framework, the purpose of this study was to examine the geographic distribution of job losses, recovery rates, and adaptive behavior after the recession for the fabricated metals manufacturing sector by measuring and comparing effects in 50 East North Central division MSAs and 50 South Atlantic division MSAs in the United States. Independent sample t tests compared average job level change rates for the tested regions. Significant differences in mean job loss rates for the two divisions occurred between 2008 and 2010 and in mean job recovery rates between 2010 and 2012. A multiple regression model analyzed the relationship of the dependent variable post-recession employment level changes with the independent variables defined as workforce demographic changes and establishment level changes as indicators of adaptive behavior. Results revealed a significant relationship between the dependent variable and shifts in the workforce demographic profile but did not reveal a significant relationship between the dependent variable and changes in the number of firms engaged in this sector. This study forms the genesis of background data for measuring cross-regional performance in the presence of external shocks and serves as a foundation for developing incentive models based on thriving sectors and regions for individuals, organizational groups, and society as a whole in engendering economic growth and well-being.
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Jefferson, Bea A. "Clusters and cluster policy : advanced manufacturing and metals industries in South Yorkshire". Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412792.
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Berglund, Lina, Filip Ivarsson i Marcus Rostmark. "Crucial Parameters for Additive Manufacturing of Metals : A Study in Quality Improvement". Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254785.
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Production by Additive Manufacturing creates opportunities to make customized products in small batches with less material than in traditional manufacturing. It is more sustainable and suitable for niche products, but entails new production demands to ensure quality. The goal of this study is to define the most crucial parameters when creating Additive Manufactured products in metal and suggest tools for quality improvement. This is done by analysing earlier studies and evaluating the standard production procedures for manufacturing by Selective Laser Melting. The results from this study stated that porosity and insufficiencies in shape are the most common factors leading to deviation in quality. To avoid it, the most crucial parameters to consider are; The laser freeform fabrication-system related parameters, hatch distance, laser power, layer thickness, fscanning pattern, scan speed and flowability of the powder. Concluded is also that crucial parameters within additive manufacturing are very dependent on the definition of quality for a certain product and can therefore vary. By continuous collection and analysis of data, the task of improving quality will be simplified.Produktion genom Additiv Tillverkning möjliggör tillverkande av skräddarsydda produkter i små batcher och med mindre material än vid traditionell tillverkning. Det är ett mer hållbart tillverkningssätt och mer passande för nischprodukter, men innebär nya produktionskrav för att säkerhetsställa bra kvalitet. Målet med denna studie är att definiera de viktigaste parametrarna vid Additiv Tillverkning av produkter i metall och föreslå verktyg för att förbättra dem. Detta genom analys av tidigare studier och utvärdering av klassiska produktionsrutiner för Selective Laser Melting. Resultaten från denna studie visar att porositet och formfel är de vanligaste faktorerna som leder till bristande kvalitet. För att undvika detta är de viktigaste parametrarna att ta i beaktande; parametrar kopplade till "laser freeform fabrication"-system, distans mellan laserstrålar, kraft på lasern, lagertjocklek, skanningsmönster, fart på skanningen och flytbarhet på pulvret. Slutsatsen pekar även på att avgörande parametrar inom Additiv Tillverkning beror på definitionen av kvalitet för en speciell produkt och kan därför variera. Genom kontinuerlig insamling och analys av data kommer förbättringen av kvalitet förenklas markant.
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Moseley, Steven Glyn. "The diffusion bonding of ceramics to metals by hot isostatic pressing". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364380.
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Davis, Trevor. "Formability and strength of sheet metals subjected to complex strain paths". Thesis, Aston University, 1985. http://publications.aston.ac.uk/11872/.
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PAKKANEN, JUKKA ANTERO. "Designing for Additive Manufacturing - Product and Process Driven Design for Metals and Polymers". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2714732.
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Additive Manufacturing (AM) has broken through to common awareness and to
wider industrial utilization in the past decade. The advance of this young
technology is still rapid. In spoken language additive manufacturing is referred as
3D printing for plastic material and additive manufacturing is left as an umbrella
term for other materials i.e. metallic materials and ceramics. As the utilization of
AM becomes more widespread, the design for additive manufacturing becomes
more crucial as well as its standardization.
Additive manufacturing provides new set of rules with different design
freedom in comparison with subtractive manufacturing methods. This is thought
to empower product driven designs. However, in the AM methods there are
process driven variables that limit the designs functions to what could be
manufactured. There are often extra steps after production to finalize the design.
Topology optimization utilizes product driven design where material is only
where it is needed to be. The design is computed without taking into account any
manufacturing constrains and only the design in the final application stage is
achieved. Topology optimization algorithm is explored in detail for two
algorithms. Then these algorithms are compared in case study I to gain better
understanding of the algorithms functions. Case study I consists of 2D and 3D
algorithms where a 3D level set method algorithm was written for this purpose.
The concept of designing for additive manufacturing is examined for
polymeric materials in case study II with a help of topology optimization design
software tailored for additive manufacturing market. The parts are manufactured
with different AM methods, examined and results are explained. The results show
an interesting effect of anisotropy and the manufacture methods effect in the part
mechanical properties.
On the other hand, process driven design and its concepts important as the
manufacturing method dictates, what can and should be done economically. Metal
AM process constraints are explored in case study III through accuracy studies in
metal additive manufacturing at laser powder bed fusion (LPBF) technology.
Accuracy and surface studies are concluded to gain a better understanding of the
process and manufacturability of metal parts. The gain knowledge is explaned and
examples are shown how these are utilized to make metal parts with tailored
properties and with minimal post processing needs.
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Hurd, Trace Q. "Chemistry, Detection, and Control of Metals during Silicon Processing". Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4771/.
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This dissertation focuses on the chemistry, detection, and control of metals and metal contaminants during manufacturing of integrated circuits (ICs) on silicon wafers. Chapter 1 begins with an overview of IC manufacturing, including discussion of the common aqueous cleaning solutions, metallization processes, and analytical techniques that will be investigated in subsequent chapters. Chapter 2 covers initial investigations into the chemistry of the SC2 clean - a mixture of HCl, H2O2, and DI water - especially on the behavior of H2O2 in this solution and the impact of HCl concentration on metal removal from particle addition to silicon oxide surfaces. Chapter 3 includes a more generalized investigation of the chemistry of metal ions in solution and how they react with the silicon oxide surfaces they are brought into contact with, concluding with illumination of the fundamental chemical principles that govern their behavior. Chapter 4 shows how metal contaminants behave on silicon wafers when subjected to the high temperature (≥ 800 °C) thermal cycles that are encountered in IC manufacturing. It demonstrates that knowledge of some fundamental thermodynamic properties of the metals allow accurate prediction of what will happen to a metal during these processes. Chapter 5 covers a very different but related aspect of metal contamination control, which is the effectiveness of metal diffusion barriers (e.g. Ru) in holding a metal of interest, (e.g. Cu), where it is wanted while preventing it from migrating to places where it is not wanted on the silicon wafer. Chapter 6 concludes with an overview of the general chemical principles that have been found to govern the behavior of metals during IC manufacturing processes.
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Al-Dira'a, Ali Abood Essa. "An investigation into the friction welding of ceramics to metals and nimonic to nimonic". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357458.
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Juckem, John R. "Aligning Sheboygan Area School District's metals/manufacturing machine tool curriculum to meet local needs". Menomonie, WI : University of Wisconsin--Stout, 2005. http://www.uwstout.edu/lib/thesis/2005/2005juckemj.pdf.
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Mylett, Terri. "The intensification of labour market polarisation in metals manufacturing in Australia in the 1990s". Thesis, School of Management, Marketing and Employment Relations, 2003. https://ro.uow.edu.au/theses/2034.
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In Australia during the 1990s, jobs offered by employers had increasingly differentiated standards of wages, conditions and security. For some workers, this has meant experiencing wages and working conditions that challenge the Australian tradition that employment will be sufficient for avoiding poverty and securing the reproduction of labour. The trend of polarisation nationally was also evident in the Metals Manufacturing industry and in the lllawarra region. The two most significant developments in Metals Manufacturing in the 1990s were (i) the rise in casual employment (including labour hire); and (ii) the masculinisation of employment in the industry, including non-standard employment. These two developments occurred in the context of prolonged decline in total employment in Metals Manufacturing. Polarisation in Metals Manufacturing was most evident in wages, hours of work and by employment status. Studying polarisation in this industry revealed a dynamic relation between the degradation and polarisation of labour market standards. The disadvantages of casual employment relative to the advantages of permanent employment mean that its expansion contributed to polarisation. But employment decline and casualisation (particularly through labour hire and outsourcing) were found to have placed pressure on the standards and working conditions of permanent workers. So degradation was evident. Nevertheless, the declioe in employment and the casualisation of employment also made permanent work much more valuable because of its relative scarcity. This change in relativity between permanent and casual employment represents polarisation, regardless of the degradation in standards experienced by permanent workers. In keeping with labour market segmentation theory, it was found that labour market trends in the 1990s were constructed upon long-standing segmentation based on sex and language-background. However, segmentation in the Metals Manufacturing industry at the end of the 1990s is different from traditional labour market segmentation because labour market disadvantage is not limited to those workers traditionally considered to have secondary or marginal status because of their sex or language-background. The causes of polarisation were considered through the lens of labour market segmentation theory, which places most weight on the role of employers when explaining labour market advantage and disadvantage. Such an explanation was assessed relative to competing explanations provided by neo-classical labour economics and by Metals Manufacturing employers that gave market forces and the choices of individual employees most weight. Segmentation theory was shown to provide a much more plausible explanation of polarisation on empirical and ontological grounds. Extensive and intensive methods were used to reach this conclusion, with the research design guided by critical realism, geography and organisation theory as well as labour market segmentation theory. The research design was aimed at explaining the labour market in terms of causal relations at multiple levels, where levels were taken to be in an interconstitutive relation rather than separate (like the way that tiles can form a mosaic while retaining their own distinctiveness). The levels studied were: the nation, the region, the industry, the workplace and that of individual employees. The research design also depended on developing a more accurate and useful conception of the employer-labour market relation. Segmentation theorists have retained the internal labour market concept from neo-classical labour economics that impedes analysis of the way that actions of one employer can influence the actions of another. A new approach to understanding the employer-labour market relation that has more explanatory power is developed and applied in this thesis. It unpacks the employer-labour market relation by distinguishing employers singularly, employers singularly as an interactive group, and employers collectively. Considering the role of employers in this way provides deeper understanding of the contemporary spatial struggle in Metals Manufacturing between employers' preferences for an enterprise-level approach to industrial relations and trade unions' preferences for an industry-level approach, and the consequences of this struggle for industrial relations, gender equity and the management of labour.
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Dimitrov, D., P. A. Hugo i B. Deez. "Suitability of layer manufacturing technologies for rapid tooling development in investment casting of light metals". Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/558.
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Published ArticleRapid tooling (RT) in the context of this research presents the possibility of improving the traditional investment casting process by shortening lead times while still maintaining affordable costs and required quality. Various rapid prototyping processes are available that can be used to create direct metal, polymer or wooden dies for this casting technology. This paper presents results gained in an AMTS project, focusing on RT development for investment casting of light metals. One of the most widely used layer manufacturing processes available in South Africa is selective laser sintering. A machine produced by the German manufacturer EOS (process known as laser sintering) utilising this technology was selected for the study. Two of the materials that are suitable for rapid die making are used, which in tum reflects different mechanical properties and process economics. A standard benchmark part was used as a study base. Two dies were built, one in alumide and one in polyamide. A comprehensive measurement programme was conducted, followed by an appropriate statistical analysis and evaluation regarding accuracy and surface finish. A number of wax patterns were produced. The best wax patterns from each die were selected and evaluated. The subsequently produced castings in AI, Mg and TI were further examined and evaluated. Various issues concerning the reinforcement, wax injection, pattern removal, accuracy and surface finish of the dies are discussed in the paper. The research concludes that rapid tooling techniques can be successfully used for creating accurate dies in order to shorten lead times in the investment casting process chain.
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Mun, Jiwon. "Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting". Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822758/.
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There is a wide range of applications for 3D printing technology with an additive manufacturing such as aerospace, automotive, marine and oil/gas, medical, consumer, electronics, building construction, and many others. There have been many pros and cons for 3D additive manufacturing. Even though 3D printing technology has many advantages: freedom to design and innovate without penalties, rapid iteration through design permutations, excellence mass customization, elimination of tolling, green manufacturing, minimal material wastes, energy efficiency, an enablement of personalized manufacturing. 3D additive manufacturing still has many disadvantages: unexpected pre- and post-processing requirement, high-end manufacturing, low speed for mass production, high thermal residual stress, and poor surface finish and dimensional accuracy, and many others. Especially, the issues for 3D additive manufacturing are on high cost for process and equipment for high-end manufacturing, low speed for mass production, high thermal residual stress, and poor surface finish and dimensional accuracy. In particular, it is relatively challenging to produce casting products with lattice or honeycomb shapes having sophisticated geometries. In spite of the scalable potential of periodic cellular metals to structural applications, the manufacturing methods of I∙AM Casting have been not actively explored nor fully understood. A few qualitative studies of I∙AM Casting has been reported. Recently, a sand casting of cellular structures was attempted, resulting in casting porosity and the sharp corners in the lattice structure of the cellular structural molds, a sharpness which prevent fluid-flow and causes undesired solidification, resulting in misrun casting defects. Research on the indirect AM methods has not been aggressively conducted due to the highly complex and multidisciplinary problems across the process – continuum modeling (thermal stress, flow, heat transfer, and water diffusion) with multiple materials (polymer, metals, and ceramic) for multiphase simulations – solid, liquid, and gas. As an initial step to fully understand the processing of I∙AM Casting, a quantitative study on I∙AM Casting is conducted in this work.
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Kasonde, Maweja. "Optimising the mechanical properties and microstructure of armoured steel plate in the quenched and tempered condition". Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-11022006-192139.
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Griffiths, Robert Joseph. "Dynamic and Post-Dynamic Microstructure Evolution in Additive Friction Stir Deposition". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104664.
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Metal additive manufacturing stands poised to disrupt multiple industries with high material use efficiency and complex part production capabilities, however many technologies deposit material with sub-optimal properties, limiting their use. This decrease in performance largely stems from porosity laden parts, and asymmetric solidification-based microstructures. Solid-state additive manufacturing techniques bypass these flaws, using deformation and diffusion phenomena to bond material together layer by layer. Among these techniques, Additive Friction Stir Deposition (AFSD), stands out as unique for its freeform nature, and thermomechanical conditions during material processing. Leveraging its solid-state behavior, optimized microstructures produced by AFSD can reach performance levels near, at, or even above traditionally prepared metals. A strong understanding of the material conditions during AFSD and the phenomena responsible for microstructure evolution. Here we discuss two works aimed at improving the state of knowledge surrounding AFSD, promoting future microstructure optimization. First, a parametric study is performed, finding a wide array of producible microstructures across two material systems. In the second work, a stop-action type experiment is employed to observe the dynamic microstructure evolution across the AFSD material flow pathway, finding specific thermomechanical regimes that occur within. Finally, multiple conventional alloy systems are discussed as their microstructure evolution pertains to AFSD, as well as some more unique systems previously limited to small lab scale techniques, but now producible in bulk due to the additive nature of AFSD.Doctor of Philosophy
The microstructure of a material describes the atomic behavior at multiple length scales. In metals this microstructure generally revolves around the behavior of millions of individual crystals of metal combined to form the bulk material. The state and behavior of these crystals and the atoms that make them up influence the strength and usability of the material and can be observed using various high fidelity characterization techniques. In metal additive manufacturing (i.e. 3D printing) the microstructure experiences rapid and severe changes which can alter the final properties of the material, typical to a detrimental effect. Given the other benefits of additive manufacturing such as reduced costs and complex part creation, there is desire to predict and control the microstructure evolution to maximize the usability of printed material. Here, the microstructure evolution in a solid-state metal additive manufacturing, Additive Friction Stir Deposition (AFSD), is investigated for different metal material systems. The solid-state nature of AFSD means no melting of the metal occurs during processing, with deformation forcing material together layer by layer. The conditions experienced by the material during printing are in a thermomechanical regime, with both heating and deformation applied, akin to common blacksmithing. In this work specific microstructure evolution phenomena are discussed for multiple materials, highlighting how AFSD processing can be adjusted to change the resulting microstructure and properties. Additionally, specific AFSD process interactions are studied and described to provide better insight into cumulative microstructure evolution throughout the process. This work provides the groundwork for investigating microstructure evolution in AFSD, as well as evidence and results for a number of popular metal systems.
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Liou, Jiann-Haw. "Study of stress developments in axi-symmetric products fabricated by forging and machining /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9737869.
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Wolcott, Paul Joseph. "Ultrasonic Additive Manufacturing: Weld Optimization for Aluminum 6061, Development of Scarf Joints for Aluminum Sheet Metal, and Joining of High Strength Metals". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449162671.
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Lindén, Marcus. "Merging Electrohydrodynamic Printing and Electrochemistry : Sub-micronscale 3D-printing of Metals". Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-330958.
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Additive manufacturing (AM) is currently on the verge of redefining the way we produce and manufacture things. AM encompasses many technologies and subsets, which are all joint by a common denominator; they build three dimensional (3D) objects by adding materials layer-upon-layer. This family of methods can do so, whether the material is plastic, concrete, metallic or living cells which can function as organs. AM manufacturing at the micro scale introduces new capabilities for the AM family that has been proven difficult to achieve with established AM methods at the macro scale. Electrohydrodynamic jet (E-jet or EHD jet) printing is a micro AM technique which has the ability to print at high resolution and speed by exploiting physical phenomena to generate droplets using the means of an electric field. However, when printing metallic materials, this method requires nanoparticles for deposition. To obtain a stable structure the material needs to be sintered, after which the deposited material is left with a porous structure. In contrary, electrochemical methods using the well-known deposition mechanism of electroplating, can deposit dense and pure structures with the downside of slow deposition. In this thesis, a new method is proposed to micro additive manufacturing by merging an already existing technology EHD with simple electrochemistry. By doing so, we demonstrate that it is possible to print metallic structures at the micro- and nanoscale with high speeds, without the need for presynthesized nanoparticles. To achieve this, a printing setup was designed and built. Using a sacrificial wire and the solvent acetonitrile, metallic building blocks such as lines, pillars and other geometric features could be printed in copper, silver, and gold with a minimum feature size of 200 nm. A voltage dependence was found for porosity, where the densest pillars were printed at 135-150 V and the most porous at 260 V. The maximum experimental deposition speed measured up to 4.1 µm · s−1 at 220 V. Faraday’s law of electrolysis could be used to predict the experimental deposition speed at a potential of 190 V with vexp = 1.8 µm · s−1 and vtheory = 0.8 µm · s−1. The microstructure of the pillars could be improved through lowering the applied voltage. In addition, given that Faraday’s law of electrolysis could predict experimental depositions speeds well, it gives further proof to reduction being the mechanism of deposition.
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Johnston, Andrew. "Knowledge spillovers among small firms : a case study of South Yorkshire's advanced manufacturing and metals cluster". Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421131.
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Khan, Abdullah. "An investigation into improving the functioning of manufacturing executions system at the Impala base metals refinery". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/6408.
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Tonelli, Lavinia <1987>. "Additive Manufacturing by LPBF and WAAM of metals: correlation between production process, microstructure and mechanical properties". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9629/1/LaviniaTonelli_PhDThesis.pdf.
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In the most recent years, Additive Manufacturing (AM) has drawn the attention of both academic research and industry, as it might deeply change and improve several industrial sectors. From the material point of view, AM results in a peculiar microstructure that strictly depends on the conditions of the additive process and directly affects mechanical properties. The present PhD research project aimed at investigating the process-microstructure-properties relationship of additively manufactured metal components. Two technologies belonging to the AM family were considered: Laser-based Powder Bed Fusion (LPBF) and Wire-and-Arc Additive Manufacturing (WAAM). The experimental activity was carried out on different metals of industrial interest: a CoCrMo biomedical alloy and an AlSi7Mg0.6 alloy processed by LPBF, an AlMg4.5Mn alloy and an AISI 304L austenitic stainless steel processed by WAAM. In case of LPBF, great attention was paid to the influence that feedstock material and process parameters exert on hardness, morphological and microstructural features of the produced samples. The analyses, targeted at minimizing microstructural defects, lead to process optimization. For heat-treatable LPBF alloys, innovative post-process heat treatments, tailored on the peculiar hierarchical microstructure induced by LPBF, were developed and deeply investigated. Main mechanical properties of as-built and heat-treated alloys were assessed and they were well-correlated to the specific LPBF microstructure. Results showed that, if properly optimized, samples exhibit a good trade-off between strength and ductility yet in the as-built condition. However, tailored heat treatments succeeded in improving the overall performance of the LPBF alloys. Characterization of WAAM alloys, instead, evidenced the microstructural and mechanical anisotropy typical of AM metals. Experiments revealed also an outstanding anisotropy in the elastic modulus of the austenitic stainless-steel that, along with other mechanical properties, was explained on the basis of microstructural analyses.
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Promoppatum, Patcharapit. "Numerical Modeling of Thermal and Mechanical Behaviors in the Selective Laser Sintering of Metals". Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1181.
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The selective laser sintering (SLS) process or the additive manufacturing (AM) enables the construction of a three-dimensional object through melting and solidification of metal powder. The primary advantage of AM over the conventional process is providing the manufacturing flexibility, especially for highly complicated products. The quality of AM products depends upon various processing parameters such as laser power, laser scanning velocity, laser scanning pattern, layer thickness, and hatch spacing. The improper selection of these parameters would lead to parts with defects, severe distortion, and even cracking. I herein perform the numerical and experimental analysis to investigate the interplay between processing parameters and the defect generation. The analysis aims to resolve issues at two different scales, micro-scale and product-scale. At the micro-scale, while the numerical model is developed to investigate the interaction of the laser and materials in the AM process, its advantages and disadvantages compared to an analytical approach (Rosenthal’s equation), which provides a quicker thermal solution, are thoroughly studied. Additionally, numerical results have been verified by series of experiments. Based on the analysis, it is found that the simultaneous consideration of multiple processing parameters could be achieved using the energy density. Moreover, together with existing criteria, a processing window is numerically developed as a guideline for AM users to avoid common defects at this scale including the lack of fusion, balling effect, and over-melting. Thermal results at a micro-scale are extended as an input to determine the residual stress initiation in AM products. The effect of energy density and substrate temperature on a residual stress magnitude is explored. Results show that the stress magnitude within a layer is a strong function of the substrate temperature, where a higher substrate temperature results in a lower stress. Moreover, the stress formation due to a layer’s addition is studied, in which the stress relaxation at locations away from a top surface is observed. Nevertheless, even though the micro-scale analysis can resolve some common defects in AM, it is not capable of predicting product-scale responses such as residual stress development and entire product’s distortion. As a result, the multiscale modeling platform is developed for the numerical investigation at the product level. Three thermal models at various scales are interactively used to yield an effective thermal development calculation at a product-scale. In addition, the influence of the multiple layers, energy densities and scanning patterns on the residual stress formation has been addressed, which leads to the prediction of the residual stress development during the fabrication. The distortion of products due to the residual stress can be described by the product-scale model. Furthermore, among many processing parameters, the energy input and the scanning length are found to be important factors, which could be controlled to achieve the residual stress reduction in AM products. An optimal choice of a scanning length and energy input can reduce an as-built residual stress magnitude by almost half of typically encountered values. Ultimately, the present work aims to illustrate the integration of the computational method as tools to provide manufacturing qualification for part production by the AM process.
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Moneghan, Matthew John. "Microstructural Deformation Mechanisms and Optimization of Selectively Laser Melted 316L Steel". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104170.
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In this paper, a novel approach is utilized to investigate the deformation mechanisms at the microstructural level in 3D printed alloys. The complex in-situ heat treatments during 3D printing leaves a unique and complicated microstructure in the as-built 3D printed metals, particularly alloys. The microstructure is made of a hierarchical stacking of some interconnected geometrical shapes, namely meltpools, grains, and cells. These are connected to each other by boundaries that might have different element compositions, and consequently, material properties, compared to the interior region of each geometrical unit. Deformation mechanisms in this microstructure are still highly unexplored, mainly because of the challenges on the way of performing experiments at the micrometer length scale. In this work, we establish an image processing framework that directly converts the SEM images taken from the microstructure of 3D printed 316L stainless steel alloys into CAD models. The model of the complicated microstructure is then scaled up, and the scaled model is 3D printed using polymeric materials. For 3D printing these samples, two polymers with contrasting mechanical properties are used. Distribution of these two polymers mimics the arrangement of soft and stiff regions in the microstructure of 3D printed alloys. These representative samples are subjected to mechanical loads and digital image correlation is utilized to investigate the deformation mechanisms, particularly the delocalization of stress concentration and also the crack propagation, at the microstructural level of 3D printed metals. Besides experiments, computational modeling using finite element method is also performed to study the same deformation mechanisms at the microstructure of 3D printed 316L stainless steel. Our results show that the hierarchical arrangement of stiff and soft phases in 3D printed alloys delocalizes the stress concentration and has the potential to make microstructures with significantly improved damage tolerance capabilities.Master of Science
Many researchers have studied the impacts of laser parameters on the bulk material properties of SLM printed parts; few if any have studied how these parts break at a microstructural level. In this work we show how SLM printed parts with complex microstructures including grains, meltpools, and cells, deform and break. The cellular network that occurs in some SLM printed parts leads to a multi-material hierarchical structure, with a stiff network of thin boundaries, and a bulk "matrix" of soft cell material. This leads to similar properties as some composites, whereby the stiff network of cell boundaries leads to increased damage tolerance. We show both computationally through finite element analysis, and experimentally through multi-material 3D fabrication, that the microstructure leads to increased crack length in failure, as well as lower toughness loss and strength loss in the event of a crack. Essentially, the complex nature of the formation of these parts (high heating and cooling rates from laser melting) leads to a beneficial microstructure for damage tolerance that has not been studied from this perspective before.
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Palanivel, Sivanesh. "Thermomechanical Processing, Additive Manufacturing and Alloy Design of High Strength Mg Alloys". Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849628/.
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The recent emphasis on magnesium alloys can be appreciated by following the research push from several agencies, universities and editorial efforts. With a density equal to two-thirds of Al and one-thirds of steel, Mg provides the best opportunity for lightweighting of metallic components. However, one key bottleneck restricting its insertion into industrial applications is low strength values. In this respect, Mg-Y-Nd alloys have been promising due to their ability to form strengthening precipitates on the prismatic plane. However, if the strength is compared to Al alloys, these alloys are not attractive. The primary reason for low structural performance in Mg is related to low alloying and microstructural efficiency. In this dissertation, these terminologies are discussed in detail. A simple calculation showed that the microstructural efficiency in Mg-4Y-3Nd alloy is 30% of its maximum potential. Guided by the definitions of alloying and microstructural efficiency, the two prime objectives of this thesis were to: (i) to use thermomechanical processing routes to tailor the microstructure and achieve high strength in an Mg-4Y-3Nd alloy, and (ii) optimize the alloy chemistry of the Mg-rare earth alloy and design a novel rare—earth free Mg alloy by Calphad approach to achieve a strength of 500 MPa.
Experimental, theoretical and computational approaches have been used to establish the process-structure-property relationships in an Mg-4Y-3Nd alloy. For example, increase in strength was observed after post aging of the friction stir processed/additive manufactured microstructure. This was attributed to the dissolution of Mg2Y particles which increased the alloying and microstructural efficiency. Further quantification by numerical modeling showed that the effective diffusivity during friction stir processing and friction stir welding is 60 times faster than in the absence of concurrent deformation leading to the dissolution of thermally stable particles. In addition, the investigation on the interaction between dislocations and strengthening precipitate revealed that, specific defects like the I1 fault aid in the accelerated precipitation of the strengthening precipitate in an Mg-4Y-3Nd alloy. Also, the effect of external field (ultrasonic waves) was studied in detail and showed accelerated age hardening response in Mg-4Y-3Nd alloy by a factor of 24.
As the bottleneck of low strength is addressed, the answers to the following questions are discussed in this dissertation: What are the fundamental micro-mechanisms governing second phase evolution in an Mg-4Y-3Nd alloy? What is the mechanical response of different microstructural states obtained by hot rolling, friction stir processing and friction stir additive manufacturing? Is defect engineering critical to achieve high strength Mg alloys? Can application of an external field influence the age hardening response in an Mg-4Y-3Nd alloy? Can a combination of innovative processing for tailoring microstructures and computational alloy design lead to new and effective paths for application of magnesium alloys?
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Schunemann, Esteban. "Paste deposition modelling : deconstructing the additive manufacturing process : development of novel multi-material tools and techniques for craft practitioners". Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/13803.
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A novel paste deposition process was developed to widen the range of possible materials and applications. This experimental process developed an increasingly complex series of additive manufacturing machines, resulting in new combinations of novel materials and deposition paths without sacrificing many of the design freedoms inherit in the craft process. The investigation made use of open-source software together with an approach to programming user originated infill geometries to form structural parts, differing from the somewhat automated processing by 'closed' commercial RP systems. A series of experimental trials were conducted to test a range of candidate materials and machines which might be suitable for the PDM process. The combination of process and materials were trailed and validated using a series of themed case studies including medical, food industry and jewellery. Some of the object created great interest and even, in the case of the jewellery items, won awards. Further evidence of the commercial validity was evidenced through a collaborative partnership resulting in the development of a commercial version of the experimental system called Newton3D. A number of exciting potential future directions having been opened up by this project including silicone fabrics, bio material deposition and inclusive software development for user originated infills and structures.
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Stephenson, Richard C. "Comparing the Feasibility of Cutting Thin-Walled Sections from Five Commonly Used Metals Utilizing Wire Electric Discharge Machining". Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1948.pdf.
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Squires, Lile P. "Friction Bit Joining of Dissimilar Combinations of Advanced High-Strength Steel and Aluminum Alloys". BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4104.
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Friction bit joining (FBJ) is a new method that enables lightweight metal to be joined to advanced high-strength steels. Weight reduction through the use of advanced high-strength materials is necessary in the automotive industry, as well as other markets, where weight savings are increasingly emphasized in pursuit of fuel efficiency. The purpose of this research is twofold: (1) to understand the influence that process parameters such as bit design, material type and machine commands have on the consistency and strength of friction bit joints in dissimilar metal alloys; and (2) to pioneer machine and bit configurations that would aid commercial, automated application of the system. Rotary broaching was established as an effective bit production method, pointing towards cold heading and other forming methods in commercial production. Bit hardness equal to the base material was found to be highly critical for strong welds. Bit geometry was found to contribute significantly as well, with weld strength increasing with larger bit shaft diameter. Solid bit heads are also desirable from both a metallurgical and industry standpoint. Cutting features are necessary for flat welds and allow multiple material types to be joined to advanced high-strength steel. Parameters for driving the bit were established and relationships identified. Greater surface area of contact between the bit and the driver was shown to aid in weld consistency. Microstructure changes resulting from the weld process were characterized and showed a transition zone between the bit head and the bit shaft where bit hardness was significantly increased. This zone is frequently the location of fracture modes. Fatigue testing showed the ability of FBJ to resist constant stress cycles, with the joined aluminum failing prior to the FBJ fusion bond in all cases. Corrosion testing established the use of adhesive to be an effective method for reducing galvanic corrosion and also for protecting the weld from oxidation reactions.
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Peterson, Rebecca Hilary. "Friction Bit Joining of Dissimilar Combinations of DP 980 Steel and AA 7075". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6030.
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Friction Bit Joining (FBJ) is a new technology that allows lightweight metals to be joined to advanced high-strength steels (AHSS). Joining of dissimilar metals is especially beneficial to the automotive industry because of the desire to use materials such as aluminum and AHSS in order to reduce weight and increase fuel efficiency. In this study, FBJ was used to join 7075 aluminum and DP980 ultra-high-strength steel. FBJ is a two-stage process using a consumable bit. In the first stage, the bit cuts through the top material (aluminum), and in the second stage the bit is friction welded to the base material (steel). The purpose of the research was to examine the impact a solid head bit design would have on joint strength, manufacturability, and ease of automation. The solid head design was driven externally. This design was compared to a previous internally driven head design. Joint strength was assessed according to an automotive standard established by Honda. Joints were mechanically tested in lap-shear tension, cross-tension, and peel configurations. Joints were also fatigue tested, cycling between loads of 100 N and 750 N. The failure modes that joints could experience during testing include: head, nugget, material, or interfacial failure. All tested specimens in this research experienced interfacial failure. Welds were also created and examined under a microscope in order to validate a simulation model of the FBJ process. The simulation model predicted a similar weld shape and bond length with 5 percent accuracy. Joints made with external bits demonstrated comparable joint strength to internal bits in lap-shear tension and cross-tension testing. Only external bits were tested after lap-shear tension, because it was determined that external bits would perform comparably to internal bits. Joints made with external bits also exceeded the standard for failure during fatigue testing. Peel tested specimens did not meet the required strength for the automotive standard. Examining specimens under a microscope revealed micro-cracks in the weld. These defects have been shown to decrease joint strength. Joint strength, especially during peel testing, could be increased by reducing the presence of micro-cracks. The external bit design is an improvement from the internal bits for manufacturability and ability to be automated, because of the less-expensive processes used to form the bit heads and the design that lends to ease of alignment.
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Martins, Marcelo Matos. "Análise da extrusão de metais pelo método dos volumes finitos". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264430.
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Orientadores: Sérgio Tonini Button, José Divo BressanTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-21T04:08:51Z (GMT). No. of bitstreams: 1 Martins_MarceloMatos_D.pdf: 11233728 bytes, checksum: 163e9bff5c80ef1c025e8c1083bed472 (MD5) Previous issue date: 2012
Resumo: A simulação numérica computacional é nos dia de hoje frequentemente aplicada na elaboração de projetos ou análise dos processos de conformação plástica dos metais. A extrusão de metais é um dos principais processos de conformação plástica e largamente aplicado na fabricação de produtos e peças na indústria metal-mecânica. Tradicionalmente, essas análises são feitas utilizando o Método dos Elementos Finitos. Entretanto, há um aumento no interesse dos pesquisadores na utilização do Método dos Volumes Finitos para este fim. A literatura sugere que o escoamento na extrusão de metais pode ser analisado pela formulação do escoamento plástico (flow Formulation). No qual, pode-se assumir como o escoamento de um fluido incompressível e viscoso. Essa hipótese pode ser assumida já que o processo de extrusão é um processo isocórico. O método MacCormack é geralmente aplicado para simular os escoamentos de fluidos compressíveis pelo Método do Volumes Finitos. No escoamento de um fluido incompressível ou no escoamento de metal não existe uma equação para a evolução da variável pressão, sendo necessário a utilização de um método de acoplamento entre a pressão e a velocidade. Este trabalho trata da apresentação de um novo esquema numérico para a determinação de informações sobre o escoamento de um fluido incompressível e viscoso e sobre o escoamento de metal em um processo de extrusão direta, ambos em regime permanente. As equações governantes foram discretizadas pelo Método dos Volume Finitos através do Método de MacCormack explícito para uma malha estruturada e co-localizada. O acoplamento entre a pressão e a velocidade foi feita pelo método SIMPLE. O novo esquema numérico foi aplicado em escoamentos incompressíveis e viscosos para a glicerina e em escoamento de metais em processos de extrusão direta para o chumbo e uma liga de alumínio. O escoamento da glicerina foi avaliado para o caso entre placas paralelas e em dutos circulares sob condição axissimétrica e obtiveram boa concordância em relação ao resultados analíticos. Os campos de velocidades obtidos para a extrusão de metal alcançaram rápida convergência, em torno de 20000 iterações, essa quantidade de iterações foi inferior a quantidade que a glicerina necessitou. Para todos os materiais analisados os resultados numéricos tiveram boa concordância em comparação com resultados analíticos e experimentais obtidas da literatura. O método MacCormack produziu resultados coerentes para o escoamento da glicerina e dos metais sem a necessidade da adição de viscosidade artificial, como sugere a sua definição. Portanto, os resultados numéricos sugerem que o método MacCormack com o SIMPLE pode ser aplicado na resolução de escoamentos de fluidos incompressíveis e na conformação de metais além da sua tradicional aplicação na resolução de escoamentos compressíveis
Abstract: Computational numerical simulation is nowadays largely applied in the design and analysis of metal forming process. Extrusion of metals is one main forming process largely applied in the manufacturing of metallic products or parts. Historically, the Finite Element Method has been applied for decades in extrusion analysis. However, recently in the academy, there is a trend to use Finite Volume Method: literature suggests that metal flow by extrusion can be analysed by the flow formulation. Thus, metal flow can be modelled such us an incompressible viscous fluid. This hypothesis can be assumed because extrusion process is an isochoric process. The MacCormack Method is commonly used to simulate compressible fluid flow by the finite volume method. However, metal extrusion and incompressible fluid flow do not present state equations for the evolution of pressure, and therefore, a velocity-pressure coupling method is necessary to obtain a consistent velocity and pressure fields. Present work proposes a new numerical scheme to obtain information about both incompressible viscous fluid flow and metal flow in the extrusion process, in steady state. The governing equations were discretized by Finite Volume Method, using the Explicit MacCormack Method to structured and collocated mesh. The SIMPLE Method was applied to attain pressure-velocity coupling. These new numerical scheme was applied to incompressible viscous fluid flow of glycerine and forward extrusion process of lead and an aluminium alloy. The numerical results for glicerine fluid flow for parallel plates and axisymmetric flow in circular tube cases had quite good agreement in relation to the analytical solutions. The incompressible metal extrusion velocity fields achieved faster convergence than for liquid glycerine after 20.000 iterations and a good agreement with analytical and experimental results obtained from literature. The MacCormack Method applied for both glycerine and metals produced consistent results without the need of artificial viscosity as employed by the compressible flow simulation approaches. Hence, the present numerical results also suggest that MacCormack Method and SIMPLE can be applied in the solution of incompressible fluid flow and metal forming processes in adition to the traditional application for compressible fluid flow
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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Morris, Jeffrey D. "Development of Experimental and Finite Element Models to Show Size Effects in the Forming of Thin Sheet Metals". ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2676.
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Abstract
An experimental method was developed that demonstrated the size effects in forming thin sheet metals, and a finite element model was developed to predict the effects demonstrated by the experiment. A universal testing machine (UTM) was used to form aluminum and copper of varying thicknesses (less than 1mm) into a hemispherical dome. A stereolithography additive manufacturing technology was used to fabricate the punch and die from a UV curing resin. There was agreement between the experimental and numerical models. The results showed that geometric size effects were significant for both materials, and these effects increased as the thickness of the sheets decreased. The demonstration presents an inexpensive method of testing small-scale size effects in forming processes, which can be altered easily to produce different shapes and clearances.
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Slater, Rebecca Victoria. "Medieval iron wire : manufacture, materials and methods; an archaeological and scientific investigation of the manufacturing technology and use of specialist metals in the production of iron wire and wire fish hooks in medieval England". Thesis, University of Bradford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525475.
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Gardner, Rebecca. "An Experimental Investigation of Friction Bit Joining in AZ31 Magnesium and Advanced High-Strength Automotive Sheet Steel". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2159.
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Friction Bit Joining (FBJ) is a recently developed spot joining technology capable of joining dissimilar metals. A consumable bit cuts through the upper layer of metal to be joined, then friction welds to the lower layer. The bit then snaps off, leaving a flange. This research focuses on FBJ using DP980 or DP590 steel as the lower layer, AZ31 magnesium alloy as the top layer, and 4140 or 4130 steel as the bit material. In order to determine optimal settings for the magnesium/steel joints, experimentation was performed using a purpose-built computer controlled welding machine, varying factors such as rotational speeds, plunge speed, cutting and welding depths, and dwell times. It was determined that, when using 1.6 mm thick coupons, maximum joint strengths would be obtained at a 2.03 mm cutting depth, 3.30 mm welding depth, and 2500 RPM welding speed. At these levels, the weld is stronger than the magnesium alloy, resulting in failure in the AZ31 rather than in the FBJ joint in lap shear testing.
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Atwood, Lorne Steele. "Friction Bit Joining of Dissimilar Combinations of GADP 1180 Steel and AA 7085 – T76 Aluminum". BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6400.
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Friction Bit Joining (FBJ) is a method used to join lightweight metals to advanced high-strength steels (AHSS). The automotive industry is experiencing pressure to improve fuel efficiency in their vehicles. The use of AHSS and aluminum will reduce vehicle weight which will assist in reducing fuel consumption. Previous research achieved joint strengths well above that which was required in three out of the four standard joint strength tests using DP980 AHSS and 7075 aluminum. The joints were mechanically tested and passed the lap-shear tension, cross-tension, and fatigue cycling tests. The t-peel test configuration never passed the minimum requirements. The purpose of continuing research was to increase the joint strength using FBJ to join the aluminum and AHSS the automotive industry desires to use specifically in the t-peel test. In this study FBJ was used to join 7085 aluminum and GADP1180 AHSS. The galvanic coating on the AHSS and its increased strength with the different aluminum alloy required that all the tests be re-evaluated and proven to pass the standard tests. FBJ is a two-step process that uses a consumable bit. In the first step the welding machine spins the bit to cut through the aluminum, and the second step applies pressure to the bit as it comes in contact with the AHSS to create a friction weld.
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Turner, David Bentley. "An assessment of Magic Metal Company". Online version, 1998. http://www.uwstout.edu/lib/thesis/1998/1998turnerd.pdf.
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PEDEMONTE, LAURA CHIARA. "Laser in Metal Additive Manufacturing". Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/973605.
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The evolution of additive manufacturing (AM) techniques has had such an exponential increase especially in recent years that various and remarkable techniques have been developed for the production of metallic materials. These techniques allow to obtain products with remarkable mechanical characteristics.
Therefore, the different AM techniques that employed metallic materials were analysed and their strengths and weaknesses were considered. In particular, investigations were carried out on artefacts made by Direct Metal Laser Sintering (DMLS) technique in two different metal alloys: Inconel-625 and titanium grade 2.
In relation to Inconel-625, tomographic analyses were carried out for the detection of ad hoc defects, ultrasound analyses to evaluate anistropy, micrographs and tensile tests to evaluate their mechanical characteristics.
The titanium grade 2 products were compared with samples made by the traditional fusion technique to assess their suitability in the dental field. The results show that artefacts made by DMLS technique have overall better features than fusion samples: the defects are less widespread and smaller, the hardness - characteristic of mechanical properties - higher.
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Jaques, Mark W. S. "Design by manufacturing simulation". Thesis, University of Portsmouth, 1994. https://researchportal.port.ac.uk/portal/en/theses/design-by-manufacturing-simulation(73339fbe-283d-4a11-a225-33cabf5e7332).html.
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An alternative approach to conventional geometric based computer aided design systems is presented. Within this new approach manufacturing modes are used as the primary input to the design process. By directly actuating a simulation of machine tools and displaying the response of the material to this machine action, manufacturing constraints are captured at the design stage. Both manufacturing and design data can be generated concurrently, leading to a reduction in prototyping development lead times. Geometric and physical models of the manufacturing process are combined through the development of an interaction rule base to form a manufacturing simulation of the bending and forming process. These interaction rules interpret interactions of the geometric models and automatically generates constraints information required by the finite element engine, which performs the physical modelling task, and allows it to be fully embedded. Design trials are presented in which designers successfully used the design by manufacturing simulation approach to design metallic fastenings significantly faster than the traditional computer aided design approach.
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Farshbaf, Mohamad Reza. "Mixed metal forming/machining flexible manufacturing system". Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277924.
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Byron, Andrew James. "Qualification and characterization of metal additive manufacturing". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104315.
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Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2016. In conjunction with the Leaders for Global Operations Program at MIT.Thesis: S.M. in Engineering Systems, Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. In conjunction with the Leaders for Global Operations Program at MIT.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-123).
Additive manufacturing (AM) has emerged as an effective and efficient way to digitally manufacture complicated structures. Raytheon Missile Systems seeks to gain limited production capability with metals AM, which can only be achieved with qualified, predictable processes that reduce variation. The project documented in this thesis produced two results needed to qualify AM for use on flight-critical parts: i) creation of a standard qualification process building upon Raytheon's product development knowledge, and ii) selection and identification of key metals AM process factors and their corresponding experimental responses. The project has delivered a qualification test plan and process that will be used next year to drive adoption and integration of Raytheon's metals AM technology. The first phase of the designed experiment on AM process factors was completed by experimenting with coupon orientation, position on the build platform, coupon shape and hot isostatic pressing (HIP) post-treatment for an Al alloy (AlSi10Mg) produced via laser powder bed fusion using 400-watt laser equipment. Only coupon orientation had a statistically significant effect on dimensional accuracy, increasing the variance of y-axis (within the build plane) error by ~50%, although this is considered a small increase. HIP decreased yield and ultimate stresses by ~60% while increasing ultimate strain by ~250%. Vertical orientation of coupons decreased yield and ultimate stresses by ~25% and increased ultimate strain by ~30%. Small coupon area on the build platform, associated with thin rectangle coupons, decreased yield stress and ultimate strain by ~5%. The processes and case study from this thesis represent a general advance in the adoption of metals AM in aerospace manufacturing.
by Andrew James Byron.
M.B.A.
S.M. in Engineering Systems
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McCarthy, David Lee. "Creating Complex Hollow Metal Geometries Using Additive Manufacturing and Metal Plating". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43530.
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Additive manufacturing introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods. Using a cellular heat exchanger as a motivational example, this thesis investigates the creation of a hybrid manufacturing approach that combines selective laser sintering with an electroforming process to produce complex, hollow, metal geometries. The developed process uses electroless nickel plating on laser sintered parts that then undergo a flash burnout procedure to remove the polymer, leaving a complex, hollow, metal part. The resulting geometries cannot be produced directly with other additive manufacturing systems.
Copper electroplating and electroless nickel plating are investigated as metal coating methods. Several parametric parts are tested while developing a manufacturing process. Copper electroplating is determined to be too dependent on the geometry of the part, with large changes in plate thickness between the exterior and interior of the tested parts. Even in relatively basic cellular structures, electroplating does not plate the interior of the part. Two phases of electroless nickel plating combined with a flash burnout procedure produce the desired geometry. The tested part has a density of 3.16g/cm3 and withstands pressures up to 25MPa. The cellular part produced has a nickel plate thickness of 800µm and consists of 35% nickel and 65% air (empty space). Detailed procedures are included for the electroplating and electroless plating processes developed.Master of Science
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Nyembwe, Kasongo Didier. "Tool manufacturing by metal casting in sand moulds produced by additive manufacturing processes". Thesis, Bloemfontein : Central University of Technology, Free State, 2012. http://hdl.handle.net/11462/162.
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Thesis (D. Tech. ( Mechanical Engineering )) - Central University of technology, Free State, 2012In this study an alternative indirect Rapid Tooling process is proposed. It essentially consists of producing sand moulds by Additive Manufacturing (AM) processes followed by casting of tools in the moulds. Various features of this tool making method have been investigated. A process chain for the proposed tool manufacturing method was conceptually developed. This process chain referred to as Rapid Casting for Tooling (RCT) is made up of five steps including Computer Aided Design (CAD) modeling, casting simulation, AM of moulds, metal casting and finishing operations. A validation stage is also provided to determine the suitability of the tool geometry and material for RCT. The theoretical assessment of the RCT process chain indicated that it has potential benefits such as short manufacturing time, low manufacturing cost and good quality of tools in terms of surface finish and dimensional accuracy. Focusing on the step of AM of the sand moulds, the selection of available AM processes between the Laser Sintering (LS) using an EOSINT S 700 machine and Three Dimensional Printing using a Z-Corporation Spectrum 550 printer was addressed by means of the Analytic Hierarchy Process (AHP). The criteria considered at this stage were manufacturing time, manufacturing cost, surface finish and dimensional accuracy. LS was found to be the most suitable for RCT compared to Three Dimensional Printing. The overall preferences for these two alternatives were respectively calculated at 73% and 27%. LS was then used as the default AM process of sand moulds in the present research work. A practical implementation of RCT to the manufacturing of foundry tooling used a case study provided by a local foundry. It consisted of the production of a sand casting pattern in cast iron for a high pressure moulding machine. The investigation confirmed the feasibility of RCT for producing foundry tools. In addition it demonstrated the crucial role of casting simulation in the prevention of casting defects and the prediction of tool properties. The challenges of RCT were found to be exogenous mainly related to workmanship. An assessment of RCT manufacturing time and cost was conducted using the case study above mentioned as well as an additional one dealing with the manufacturing of an aluminium die for the production of lost wax patterns. Durations and prices of RCT steps were carefully recorded and aggregated. The results indicated that the AM of moulds was the rate determining and cost driving step of RCT if procurement of technology was considered to be a sunk cost. Overall RCT was found to be faster but more expensive than machining and investment casting. Modern surface analyses and scanning techniques were used to assess the quality of RCT tools in terms of surface finish and dimensional accuracy. The best surface finish obtained for the cast dies had Ra and Rz respectively equal to 3.23 μm and 11.38 μm. In terms of dimensional accuracy, 82% of cast die points coincided with die Computer Aided Design (CAD) data which is within the typical tolerances of sand cast products. The investigation also showed that mould coating contributed slightly to the improvement of the cast tool surface finish. Finally this study also found that the additive manufacturing of the sand mould was the chief factor responsible for the loss of dimensional accuracy. Because of the above, it was concluded that light machining will always be required to improve the surface finish and the dimensional accuracy of cast tools. Durability was the last characteristic of RCT tools to be assessed. This property was empirically inferred from the mechanical properties and metallographic analysis of castings. Merit of durability figures of 0.048 to 0.152 were obtained for the cast tools. It was found that tools obtained from Direct Croning (DC) moulds have merit of durability figures three times higher than the tools produced from Z-Cast moulds thus a better resistance to abrasion wear of the former tools compared to the latter.
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GALATI, MANUELA. "Design of product and process for Metal Additive Manufacturing - From design to manufacturing". Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2688272.
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Additive Manufacturing (AM) is a recent new manufacturing approach that is based on the fabrication of each object using a layer-by-layer strategy. From a manufacturability perspective of components, this approach involves the possibility to manufacture parts of any geometric complexity without using additional tools and machines. Particular attention is dedicated to the powder bed fusion (PBF) AM processes in which a laser beam or an electron beam is used to sinter or melt metallic powders which are named Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In fact, in these last years, growing interesting of the industry has been outlined for metal AM, because they offer exclusive benefits such as the direct production of complex functional and/or end-usable parts made with excellent materials. Today it is thus recognised the need for guidelines and tools for effective introduction of the AM processes in the metal industry. To address this issue the aim of the presented thesis was to propose concurrent engineering (CE) tools based on a comprehensive approach from design to manufacturing. The metal PBF-AM processes have been dealt by two subsequent steps. The first one addressed the development of a process selection (PS) tool that combines materials, processes and designs for the choice of the best alternative to produce a metal component. The second one concerned with the development of a model for the process simulation that can contribute to the understanding of the process.
The proposed PS tool aimed to introduce the metal AM processes as alternative to producing components. In particular, the tool was implemented in order to consider the comparison between different metal AM manufacturing processes as well as AM, machining and casting. In this approach, each alternative is represented by a combination of the design, material and process features. A well-structured open architecture for PS has been suggested. The tool works by considering the requirements of the component regarding geometry constraints and specifications. A methodology based on mathematical modeling design decisions involving multiple attributes was suggested to assess the technical and economic aspects in order to analyse and rank the alternatives. For this purpose, an index, called DePri, was introduced to resume technical aspects and offers a quantitative comparison between the alternatives. On the other, the economic aspect for AM has been addressed by providing a detail model cost. The results of the process selection in which the technical aspect of each alternative has been considered and the alternatives can be compared with the corresponding manufacturing cost. An application of the proposed tool was demonstrated by an industrial case study in which the objective was to assess the best technology resource between 3-axis CNC machining, SLM and EBM for future investments of the company in the AM technologies.
The second issue addresses the optimisation of the metal PBF-AM process by virtual simulation for a suitable selection of the process parameters. In this context, the resulting review showed the SLM as a consolidated process respect to process simulation while EBM has received less attention despite the numerous applications in the medical and aerospace fields. In order to improve the effectiveness and reliability of EBM FE simulation, a new type of modelling has been introduced for the energy source and the powder material properties which have been included in a thermal numerical model. The potential of the proposed modelling was demonstrated using comparison with existing experimental literature data for a single straight line, existing model in published literature and experimental measurements for multibeam and continuous line melting. The model was then used to investigate the effects of the process parameters on the microstructures of a TiAl alloy.
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Trumper, Richard Leslie. "Fabrication of metal matrix composites by low pressure liquid metal infiltration". Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358941.
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Scott, Andrew James. "Automated nesting of sheet metal parts". Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320561.
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Kodira, Ganapathy D. "Investigation of an Investment Casting Method Combined with Additive Manufacturing Methods for Manufacturing Lattice Structures". Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283786/.
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Cellular metals exhibit combinations of mechanical, thermal and acoustic properties that provide opportunities for various implementations and applications; light weight aerospace and automobile structures, impact and noise absorption, heat dissipation, and heat exchange. Engineered cell topologies enable one to control mechanical, thermal, and acoustic properties of the gross cell structures. A possible way to manufacture complex 3D metallic cellular solids for mass production with a relatively low cost, the investment casting (IC) method may be used by combining the rapid prototyping (RP) of wax or injection molding. In spite of its potential to produce mass products of various 3D cellular metals, the method is known to have significant casting porosity as a consequence of the complex cellular topology which makes continuous fluid's access to the solidification interface difficult. The effects of temperature on the viscosity of the fluids were studied. A comparative cost analysis between AM-IC and additive manufacturing methods is carried out. In order to manufacture 3D cellular metals with various topologies for multi-functional applications, the casting porosity should be resolved. In this study, the relations between casting porosity and processing conditions of molten metals while interconnecting with complex cellular geometries are investigated. Temperature, and pressure conditions on the rapid prototyping – investment casting (RP-IC) method are reported, thermal stresses induced are also studied. The manufactured samples are compared with those made by additive manufacturing methods.
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Ranjan, Rajit. "Design for Manufacturing and Topology Optimization in Additive Manufacturing". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307951.
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Holtz, Heath M. (Heath Mikal). "Re-sourcing manufacturing processes in metal forming operations". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34859.
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Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division; in conjunction with the Leaders for Manufacturing Program at MIT, 2005.Includes bibliographical references (p. 75-76).
Deciding which activities to conduct in-house and which to outsource has become increasingly important due to its implications on a company's supply chain and overall business model. A number of factors can lead a company to outsource manufacturing processes. As a result of this outsourcing, the supply chain can become very complex and overwhelming to manage. This thesis will analyze this situation from the perspective of one manufacturer, American Axle and Manufacturing, Inc. (AAM). AAM's Metal Formed Products (MFP) Division currently has a number of challenges: rising steel prices, fixed labor costs and declining sales. All these factors have significantly impacted profitability, forcing senior management to take a comprehensive look at the division and consider developing a plan to improve divisional operations. As a part of this plan, MFP Division's senior management asked for a thorough look into all of the manufacturing processes performed by the division both internally and by outside suppliers. In addition to identifying the processes and suppliers, senior management sought to highlight opportunities for improving the process flow through the re-sourcing of manufacturing processes. This project develops a framework to analyze and evaluate these re-sourcing decisions. This framework employs a five-step approach and incorporates a number of diverse analytical tools. Process flow mapping provided a tool to visually highlight the best opportunities to resource. In addition to a visual representation, process flow mapping also provided the data to financially evaluate alternatives. Strategic and market factors were identified in order to target and prioritize re-sourcing efforts.
(cont.) This framework provides a structure for sourcing decisions that balances the financial and strategic concerns. The project concluded in a $2M investment to re-source heat treating to AAM facilities.
by Heath M. Holtz.
S.M.
M.B.A.
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Pereira, M. F. V. T., M. Williams i R. Bruwer. "Rapid die manufacturing using direct laser metal deposition". Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/542.
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Published ArticleGlobal issues such as energy and climate changes have impacted on both the automotive and aerospace industries, forcing them to adopt measures to produce products that consume fewer combustibles and emit less carbon dioxide. Making vehicles lighter is one of the logical ways of reducing fuel consumption. The need for light components, able to fulfil technical and quality specifications, led to market growth for tooling that is able to mass produce parts using manufacturing processes such as high pressure die casting. Competitive pressures to reduce the lead time required for tooling-up has also increased dramatically. For this reason research into various methods, techniques and approaches to tool manufacture is being undertaken globally. This paper highlights the work undertaken at the CSIR on the issue of rapid die manufacturing through the application and evaluation of a rapid prototyping technique and coating technologies applied to die components of a high pressure casting die for the production of aluminium components. Criteria for determining suitability were developed against which the technique was evaluated that included time, cost and life-expectancy. Results of accelerated testing procedures to evaluate the die material produced by the rapid prototyping technique and surface coatings and treatments of die materials for their resistance to washout, erosion, heat checking and corrosion in a high pressure die casting environment, are presented. The outcomes of this research will be used for further development and application of specific techniques, design principles and criteria for this approach.