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Identification of Key Activities Contributing to Macro Plastic Waste Flows on the Shoreline of Koh Chang, Thailand : A Quantification of Macroplastic Waste Items / Identifiering av nyckelaktiviteter som bidrar till flöden av makroplastavfall på kuststräckorna på ön Koh Chang, ThailandTarus, Anita, Juell-Skielse, Elea January 2019 (has links)
Sustainable development is vital in order for Thailand to continue to develop as in previous years. However, sustainable development cannot be achieved if the amount of macroplastic littering into the oceans does not decrease. In order to facilitate future decision making regarding this issue, this report aims to identify which human activities that contribute the most to the present macroplastic waste items on Thai shorelines. This identification was performed through a simplified material flow analysis based on observations and simple calculations on the island Koh Chang in Ranong. A comparative study was performed on the dissimilar island Koh Larn in Pattaya in order to eliminate any error factors caused by the specific environment on Koh Chang. It was deduced that Grocery Consumption, Fishing and Dining were the Key Activities on the two islands that contributed to the present macroplastic waste. Tourism was also shown to be a great contributor. The study did not find any signs of a current Rate of Accumulation on Koh Chang. However, there were always macroplastic waste items present in the sampling areas which implies that they might pose a threat to the ecosystems. Further research is needed in order to find a suitable solution for this problem. / En hållbar utveckling är central för att Thailand ska kunna fortsätta utvecklas på samma sätt som skett de senaste åren. Hållbar utveckling kan dock inte uppnås om mängden makroplaster som hamnar i haven inte minskar. För att underlätta framtida beslutsfattande ämnar denna rapport att identifiera de mänskliga aktiviteter som i störst utsträckning bidrar till de makroplastföremål som går att finna på thailändska kuststräckor. Denna identifiering utfördes genom en simplifierad materialflödesanalys som baserades på observationer och simpla beräkningar på ön Koh Chang i Ranong. En jämförande studie utfördes på den annorlunda ön Koh Larn i Pattaya för att eliminera felfaktorer som kan ha uppstått på grund av Koh Changs specifika förutsättningar. Studien visade att Livsmedelskonsumption, Fiske, och Restaurangbesök var de Nyckelaktiviteter som bidrog till det befintliga makroplastavfallet. Turism visade sig också vara en stor bidragare till makroplastavfall. Studien kunde inte visa på någon Ackumuleringsgrad på Koh Chang. Trots detta fanns alltid makroplastföremål närvarande i provtagningsområdena på Koh Chang, vilket antyder att dessa föremål skulle kunna innebära ett hot mot ekosystemen. Vidare efterforskningar krävs för att hitta en passande lösning på problemet.
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Logistikprinciper : En gradering av befintliga logistikprinciper på Scanias motorbearbetning / Logistics principlesAmanbaeva, Aijan, Arefin, Aboni January 2018 (has links)
Denna rapport behandlar logistikprinciper som innebär olika logistiska strategier för att uppnå bästa möjliga arbetsmetod. På Scanias motorbearbetning är de logistikprinciper som följs idag mestadels baserade på tidigare erfarenheter och därmed saknar den vetenskaplig grund. Syftet med rapporten är att analysera teorier inom logistik och styrka de logistikprinciper som tagits fram av logistikavdelningen på Scanias motorbearbetning samt rangordna dem. I teoridelen har fokus legat på att ge en större insikt i ämnet logistikprinciper samt att benämna andra principer som påverkar logistiken på Scania. Insamling av de grundläggande teorier som rapporten innehåller utfördes genom en litteraturstudie där kurslitteraturer och datainsamling bearbetades. Intervjuer och enkätundersökning har utförts bland personalen på den berörda avdelningen för att samla in information som ger en bättre bild av nuläget. För att rangordna principerna användes ett teoretiskt mätinstrument, Analytic Hierarchy Process (AHP), som går ut på att analysera ett beslutsproblem. Metoden kan tydligt visualisera hur olika parametrar har inverkan på varandra i en hierarkisk struktur och hur parvisa jämförelser ger en prioriteringsordning av indata. Logistikprinciperna delades in i fyra kategorier och användes som indata i AHP-analysen. Resultatet användes sedan som grund till prioriteringsordningen av logistikprinciperna. / This report is about logistics principles that involve different logistics strategies to achieve the best working method which helps to improve a work environment and optimize productivity. The logistics principles that are being used today on Scania’s engine processing workshop are mostly based on past experiences and therefore there is a lack of scientific basis. The purpose of the report is to analyze theories within logistics and then based on facts confirm and rank the principles that has been developed by the Logistics Department of Scania’s engine processing workshop. In theory part, the focus has been on giving a greater insight into the subject of logistics principles and term other principles that affect logistics at Scania. The collection of the theories for the report was conducted through a literature study where course literature and data collection were processed. Interviews and surveys have been conducted among the staff of the relevant department to gather information that gives a better picture of the current situation. In order to rank the principles, a theoretical measuring instrument called Analytical Hierarchy Process (AHP) was used to analyze a decision problem. The method can visualize how different parameters have an impact on each other and how paired comparisons provide a priority order of input. The logistics principles were divided in four categories and used as inputs in the AHP analysis. The result was then used to rank the logistics principles.
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Stress dependent flow behavior in sublevel caving minesMattsson, Linde January 2022 (has links)
Sublevel caving is an underground mass mining method that utilizes the gravity-induced material flow for ore extraction. The granular flowbehavior is one of the main phenomena describing this mining method’s efficiency; therefore, a good understanding of the flow behavior is essential.The knowledge of the material flow behavior evolved in the late 1950:s when the mining method became more commonly used. However, due tothe complexity of the granular material flow, all parameters are not well studied, and a lack of knowledge still exists. With the increasing mining depths, higher stresses will occur inside the rock mass. How these increased stresses influence flow behavioris one of the parameters that are not well studied. Unfortunately, manipulating these is challenging in physical material models and mighteven be impossible in field experiments. However, achieving such control is possible using a discrete element method software. The model developedfor this thesis simulates pre-stressed rock mass up to 50 MPa and monitors the flow behavior in the software PFC3D. The result showed that the increased stress had the potential of causing a stable configuration of material inside the opening ring, known as a hangup.The hang-up later was destabilized when the blast continued to the next ring. For the chosen blasting geometry, the shape of the draw zone of thematerial that reached the extraction point did not seem to be affected by the stresses. / Skivrasbrytning är en gruvbrytningsmetod som nytjar flödet av material som skapas av graviationen och dess effektivitet är starkt kopplad tillbetendet hos materialflödet. Sedan gruvbrytningsmetoden blev allt vanligare i slutet av 1950-talet har ett flertal experiments konstrueratsför att utvärdera de parametrar som har antagits ha en inverkan på flödet, vilket resulterat i en effektivare gruvbrytningsmetod. På grund avkomplexiteten hos materialflödet är inte alla parametrar lika väl studerade, och brist på kunskap existerar fortfarande. Med de fortsatt ökande djupen i gruvorna, förväntas allt högre spänningar inuti berget, och hur dessa påverkar materialflödet är inte välstuderat. Dessa spänningar är svåra att kontrollera i både materialmodeller och vid fältförsök. Med distinkt elementmetodprogramvara kan däremotspänningarna i berget kontrolleras och flödesbeteendet studeras. I den modell som byggts för detta arbete utvärderas spänningar upp till 50 MPai programvaran PFC3D. Resultatet från simuleringarna utförda i PFC3D visade att de ökade spänningarna kan orsaka upphängning av materialet i öppningskransen.Flödet återupprättades när brytningen fortgick till nästa krans. Utöver detta studerades flödesbeteendet av det material som nådde uttagspunkten,där visade resultatet att omgivningstrycket inte har en inverkan på flödet för den valda sprängningsgeometrin.
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Developing an Accurate Simulation Model for Predicting Friction Stir Welding Processes in 2219 Aluminum AlloyBrooks, Kennen 14 December 2022 (has links)
Modeling of friction stir welding (FSW) is challenging, as there are large gradients in both strain rate and temperature that must be accounted for in the constitutive law of the material being joined. Constitutive laws are most often calibrated using flow stresses from hot compression or hot torsion testing, where strain rates are much lower than those of the FSW process. As such, the current work employed a recently developed method to measure flow stresses in AA 2219-T67 at the high strain rates typical of FSW. These data were used in the development of a finite element simulation of FSW to study the effect of the new flow stress data on temperature, torque, and load predictions, compared to standard material models calibrated with hot compression or hot torsion data. It was found that load predictions were significantly better with the new material law, reducing the error with respect to experimental measurements by approximately 79%. Because heat generation during FSW is primarily a function of friction between the rapidly spinning tool and the workpiece, the choice of friction law, and associated parameters, were also studied with respect to FE model predictions. It was found that the Norton (viscoplastic) friction law was the most appropriate for modeling FSW, because its predictions were more accurate for both the transient and steady-state phases of the FSW plunge experiment. The postulated reason for the superior performance of the Norton law was its ability to account for temperature and rate sensitivity of the workpiece material sheared by the tool, while the Tresca limited Coulomb law favored contact pressure, with essentially no temperature or rate dependence of local material properties. The combination of the new flow stress data and the optimized Norton friction law resulted in a 63% overall reduction in model error, compared to the use of a standard material law and boilerplate friction parameters. The overall error was calculated as an equally weighted comparison of temperatures, torques, and forces with experimentally measured values.
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Efficient internal material flow of boxes to gain a well-organized supply of components : A case study at Scania engine assemblyCarlsson, David, Nilsson, Björn January 2017 (has links)
Within manufacturing organizations, the material flow is a promoted part of the supply chain to evaluate, since it often stands for a significant part of the costs. The evaluation refers to the analysis and optimization of the material flow that arise during manufacturing of products. It can focus on very different levels, such as the material flow in a region or within a company’s internal processes. However, the material flow is concerned with the transportations, operations and storages of materials. A well-organized material flow enables organizations to cutting costs and increase competitiveness, via increased effectiveness and efficiency of operating practices. Scania operates in the automotive industry and they are constantly striving to improve their supply chain in terms of productivity and lower costs, to meet the needs of the market and gain increased competitiveness. Today, Scania engine assembly in Södertälje has operations in two main buildings, approximately one km in-between. One building is the material warehouse, and the other building is the actual assembly. In the future, the two building will be joint together. Consequently, the project logistics department of Scania engine assembly has recognized a possibility to re-organize and improve the material flows. The upcoming merge between the two buildings enables a possibility to investigate how the current material flows could be more efficient, before they are applied in the future state. The purpose of this research is to investigate and improve a material flow, box flow, within an automotive environment. A box flow is concerned with smaller components that use plastic boxes as packaging material. The objective is to derive a more efficient process for the flow of supplying boxes to the assembly building. By efficiency, it is defined as shorter total lead time, higher capacity, lower time/cost per box delivered, and a maintained or improved ergonomics during manual handling operations within the box flow. To fulfil the purpose of this research interviews, observations and data collections have been used to gain an understanding of how the current situation is managed at Scania engine assembly. Conducted benchmarking and literature research have been used to gain an understanding of how other companies in the industry, as well as departments at Scania, are managing their box flows. The findings have been analysed, where the different flow of boxes have been compared with the theoretical frame of reference as well as against each other. The conclusions of the analysis are different key factors, for better logistics efficiency, when managing a box flow. These key factors are providing an increased theoretical understanding, when the aim is to make a material flow of boxes more efficient, in an assembly environment. In this research, they are utilized as guidelines, to derive a more efficient process for the flow of supplying boxes. That is, implementing the findings theoretically into a practical context. To derive a more efficient process, a Business Case have been conducted. Its outcome provides a concept of how the process of boxes should be organized. That is, how the different material handling operations and equipment should be utilized to achieve an overall increased efficiency. How the box flow should be organized are presented as recommendations, which works as guidelines and insights for Scania engine assembly. They are jointly fulfilling the purpose of this research, together with the other achieved research questions. / Inom tillverkningsorganisationer är materialflödet en prioriterad del av försörjningskedjan att utvärdera, eftersom den ofta står för en betydande del av kostnaderna. Utvärderingen avser analys och optimering av materialflödet som uppstår vid tillverkning av produkter. Den kan fokusera på många olika nivåer, som materialflödet i en region eller inom ett företags interna processer. Materialflödet berör emellertid transporten, operationerna och materiallager. Ett välorganiserat materialflöde gör det möjligt för organisationer att sänka kostnaderna och öka konkurrenskraften, genom ökad inre- och yttre effektivitet av utföranden inom företaget. Scania verkar inom bilindustrin och strävar ständigt efter att förbättra sin försörjningskedja när det gäller produktivitet och lägre kostnader, för att möta marknadens behov och öka konkurrenskraften. Idag har Scanias motormontering i Södertälje verksamheter i två huvudbyggnader, med ca en kilometer mellan varandra. Den ena byggnaden är materiallagret, och den andra byggnaden är den faktiska monteringen. I framtiden kommer de två byggnaderna att bli integrerade. Följaktligen har projektlogistikavdelningen vid Scanias motormontering bedömt en möjlighet att organisera och förbättra deras materialflöden. Den kommande integrationen mellan de två byggnaderna gör det möjligt att undersöka hur de aktuella materialflödena kan bli effektivare, innan de appliceras i det framtida tillståndet. Syftet med denna forskning är att undersöka och förbättra ett materialflöde, boxflöde, i en monteringsmiljö. Ett boxflöde behandlar mindre komponenter som använder plastlådor som förpackningsmaterial. Målet är att klarlägga en effektivare process för flödet av boxar till monteringsbyggnaden. Effektivitet definieras som ett flöde som har kortare total ledtid, högre kapacitet, lägre tid / kostnad per box levererad och en bibehållen eller förbättrad ergonomi under manuella hanteringar. För att uppfylla syftet med forskningen har olika typer av intervjuer, observationer och datasamlingar använts, för att skapa en djupare förståelse över den nuvarande situationen hos Scanias motormontering. Genomförd benchmarking och litteraturforskning har använts för att förstå hur andra företag inom branschen, även andra avdelningar på Scania, hanterar sina boxflöden. Den insamlade empirin har använts i en analys där de olika flödena av boxar har jämförts både med den teoretiska referensramen samt varandra. Konklusionerna från analysen är presenterade som nyckelfaktorer för att öka effektiviteten vid hantering av boxföden. Dessa nyckelfaktorer ger en ökad teoretisk förståelse, när syftet är att skapa ett effektivare materialflöde i form av boxar, i en monteringsmiljö. I denna forskning används nyckelfaktorerna som riktlinjer för att skapa en effektivare process för flödet av boxar. Det vill säga, att implementera nyckelfaktorerna teoretiskt i ett praktiskt sammanhang. För att ta fram en effektivare process har ett Business Case realiserats, som presenterar hur samtliga processer inom boxflödet borde organiseras på fallföretaget. Det vill säga, hur olika materialhanteringsoperationer och utrustningar borde användas för att uppnå en ökad effektivitet som helhet. Hur boxflödet ska organiseras presenteras som rekommendationer. Dessa bidrar med insikter och riktlinjer för hur Scanias motormontering borde organiseras, gällande deras interna materialflöde. Tillsammans med resterande forskningsfrågor uppfyller rekommendationerna syftet med forskningen.
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Rate Effects in Bulk FormingForster, James Allam 12 1900 (has links)
<p> One of the major industrial metalworking processes is extrusion
and it is of technological importance to be able to estimate the loads
and material flow characteristics within the deforming metal. Hot
metals and superplastic materials are particularly sensitive to the
speed of the operation al though it is difficult to col".sider this in an
analysis of the problem. </p> <p>
This thesis reviews the analytical techniques available to the
engineer to determine the loads in bulk forming processes and examines the way in which rate effects have been accommodated. The upper bound method, which is an approximate analytical technique, is reviewed in detail. The concept of a tangential shear zone of constant shear strain
rate is introduced and used to enable strain rate effects to be
considered within the upper bound technique. The work rate across each discontinuity is shown to be a function of the material strain rate
sensitivity, the shear zone width and the tangential veloc i ty change. </p>
A number of tangential velocity fields are proposed for the side
extrusion process. These are examined and compared by minimizing the
work rate using a computer optimization technique. The optimum solution
for a simple tangential velocity discontinuity field is shown to give
load estimates which are within 10% of those given by the more exact
slip-line field method. </p> <p>
Experiments, performed by the author on the side extrusion of two materials, which have very different strain rate sensitivities, are
reported in detail. A characteristic difference in the extrudate
geometry for the two materials is identified and shown to be a result of
the difference in the materials strain rate sensitivity index. The
experimental extrusion pressures for the two materials at different ram
velocities are compared with theoretical values derived using the theory
developed earlier in the thesis; the correlation is good. </p> <p>
The shape of the tangential discontinuity between a uniform
translational and uniform rotational field is examined and shown to be a circular arc. A number of new tangential velocity discontinuity fields
are presented for a variety of common metalworking processes. These fields comprise straight and circular discontinuities and represent a
new type of "mixed" field which predicts the rotation of the extrudate. </p> / Thesis / Doctor of Philosophy (PhD)
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An Analysis of EV Battery Key Materials Demand on the Path Towards Carbon Neutrality in SwedenSu, Hui, Lidé, Aron January 2023 (has links)
The Swedish government has set a goal to have zero net greenhouse gas emissions by 2045 andto reduce emissions from domestic transport by at least 70% compared to 2010 levels by 2030.To achieve this, an expansion of the Swedish electric vehicle (EV) personal car fleet is needed.This scientific paper utilizes material flow analysis (MFA) to predict this expansion and thecorresponding demand for battery raw materials in Sweden, examining the growth trajectory ofthe EV market in Sweden and its implications going forward. The study concluded that themarket share of electric vehicles in Sweden will increase significantly in the next ten years,which will lead to a rise in the need for battery raw materials. Depending on possiblebreakthroughs in battery technology, these demands will vary. Given the rising demand for rawmaterials and the high environmental costs associated with mining new minerals, it is importantto underscore the importance of battery recycling as an essential component of sustainablemobility. This highlights the need to improve recycling practices.
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Bioplastics Material Flow Analysis And Their Environmental Impacts / Bioplasters materialflödesanalys och deras miljöpåverkanQin, Xinyi January 2022 (has links)
This research is conducted to have a better understanding on the future develop- ment of bioplastics and their environmental impacts. This research first studies the future consumption and waste of bioplastics till 2050 by material flow analysis (MFA). Life cycle assessment is used to assess the environment impacts of three plastics (bio-PET, PEF and petrol-PET). The total consumption of bioplastics will be near 5 million tons in 2050 and the waste will be near 4 million tons. The environment of PEF is the highest among the compared plastic types; Coal as the energy input has the would affect the environment more than other two energy inputs; Sugarcane has the lowest environment impacts among three raw materials. / Denna forskning genomförs för att få en bättre förståelse för den framtida utvecklingen av bioplaster och deras miljöpåverkan. Först studeras den framtida förbrukningen och avfallet av bioplaster fram till 2050 med hjälp av materialflödesanalyser (MFA). Förbrukningen av bioplaster analyseras för olika tillämpningar. ODYM-modellen används för att beräkna MFA. Två parametrar används som indata i modellen. Den ena är den framtida bioplastförbrukningen som beräknas genom att världsbefolkningen multipliceras med den genomsnittliga produktionskapaciteten per capita, och den andra är livslängden per tillämpning. Tolv bioplasttyper har valts ut för denna analys. Dessa plaster är bio-PET, bio-PE, bio-PA, PTT, PEF, bio-PUR, bio-PP, PLA, PHA, PBAT, PBS och PCL. Den framtida konsumtionen av bioplaster och avfallsmängderna kommer att fortsätta att öka. Den totala förbrukningen av bioplaster kommer att vara nära 5 miljoner ton år 2050 och avfallet kommer att vara nära 4 miljoner ton. Den totala förbrukningen av biopur kommer att vara den högsta av alla elva bioplaster. Den tillämpning där förbrukningen av bio-PA är störst är konsumtionsvaror och beläggningar. Bio-PET kommer också att användas i stor utsträckning som förpackningsmaterial. Livscykelanalys används för att bedöma miljöpåverkan från tre plaster (bio-PET, PEF och petrol-PET). Bedömningen genomförs med hjälp av elva scenarier som är indelade i tre grupper: olika energitillgångar, inklusive kol, hy- dropower och naturgas, och global blandad energi; olika produkter, inklusive bio-PET, PEF och petrol-PET; olika råvaror: sockerrör från Brasilien, majs från USA och potatis från Schweiz. Denna bedömning kvantifieras i sex konsekvenskategorier: global uppvärmning, markanvändning, vattenförbrukning, människors hälsa, ekosystem och markanvändning. PEF:s miljöpåverkan är störst bland de jämförda plasttyperna, kol som energibärare påverkar miljön mer än de andra två energibärarna och sockerrör har den lägsta miljöpåverkan bland de tre råvarorna.
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Clinching of AA7075 Aluminum SheetsAtia, Mostafa January 2018 (has links)
Weight reduction, increased fuel economy, and increased safety of structures in transportation applications has led to much interest in lightweight higher strength structural aluminum alloys. Suitable joining techniques to create such structures with aluminum sheets are required. Generally, similar and dissimilar sheet metals can be joined by adhesive bonding, welding, and mechanical fastening. Difficulty of welding and long processing times for adhesive bonding make mechanical fastening a process of much interest for joining of high strength aluminum sheets.
Among the different mechanical fastening techniques available in manufacturing, clinching is a common method of joining by forming in which a punch and die are used to form a geometrical interlock. However, the process introduces surface steps on both sides of the joined sheets where one side consists of a protrusion and the other a pit. Also, clinch joining, a well-accepted and widely used process for joining ductile sheet metals, is more challenging for high strength lower ductility aluminum sheets such as AA7075.
The current work aims at studying clinch-ability of high strength lower ductility AA7075 aluminum sheets of different tempers by conventional as well as a new clinching technique called "die-less" clinching. A new tooling was designed in order to conduct die-less clinches. The results showed that room temperature clinching is possible for the softer tempers namely solution treated and annealed states. However, the peak aged sheets failed to form a successful joint. A novel electrical resistance heating technique (ERH) to provide ductility to the joined sheets was used to obtain die-less clinched joints in AA7075-T6. ERH technique provides a large range of heating temperatures from room temperature to 270°C for a current duration of 3 sec. The AA7075-T6 sheets showed a superior joining by using ERH. The joint showed a metallurgical locking mechanism in addition to the commonly available form locking mechanism. / Thesis / Doctor of Philosophy (PhD) / Clinching is a common method of joining sheet metals by forming. A punch and die are used to form a permanent geometrical interlock. However, the process introduces surface steps on both sides of the joined sheets where one side consists of a protrusion and the other a pit. Clinch joining is a well-accepted and widely used process for joining ductile sheet metals. Joining of high strength lower ductility aluminum sheets such as AA7075 is more challenging.
The current work aims at joining AA7075 aluminum sheets of different tempers by clinching using the conventional method as well as a new clinching technique called "die-less" clinching. The study includes a new tooling design in order to conduct die-less clinches. Also, a novel electrical resistance heating technique (ERH) to provide ductility to the joined sheets was used to obtain die-less clinched joints in the peak aged AA7075-T6. ERH technique provides a large range of heating temperatures from room temperature to 270°C for a current duration of 3 sec. The AA7075-T6 sheets showed a superior joining by using ERH.
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Material Flow and Microstructure Evolution during Additive Friction Stir Deposition of Aluminum AlloysPerry, Mackenzie Elizabeth Jones 02 September 2021 (has links)
Serious issues including solidification porosity, columnar grains, and large grain sizes are common during fusion-based metal additive manufacturing due to the inherent melting and solidification that occurs during printing. In recent years, a high-temperature, rapid plastic deformation technique called additive friction stir deposition (AFSD) has shown great promise in overcoming these issues. Because the deposited material stays in the solid state during printing, there are no melting and solidification events and the process can result in as-printed material that is fully-dense with equiaxed, fine grains. As AFSD is an emerging process, developing an understanding of the synergy between material deformation and the resultant microstructure evolution, especially the strain magnitude, its influence on dynamic microstructure evolution, and material flow details, is imperative for the full implementation of AFSD. Therefore, the purpose of this work is to investigate the severe plastic deformation in AFSD through complementary studies on the concurrent evolution of shape and microstructure during the deposition of dissimilar aluminum alloys. In this work, we systematically study (1) the entire deposition via dissimilar cladding along with (2) specific volumes within the deposited layer via embedded tracers printed at varied processing parameters. X-ray computed tomography and electron backscatter diffraction are employed to visualize the complex shape of the deposits and understand the microstructure progression.
Investigation of dissimilar cladding of homogeneous AA2024 feed-rods onto an AA6061 substrate establishes a working understanding of the mechanisms related to material flow and microstructure evolution across the whole deposit (macroscopic shape evolution) as well as at the interface between the deposit and the substrate. Variations in tooling and rotation rate affect the interfacial features, average grain size, and depth of microstructural influence. The non-planar and asymmetric nature of AFSD on the macro-scale is revealed and a maximum boundary of deposited material is established which gives a frame of reference for the next material flow study within the deposition zone.
An understanding of the mesoscopic morphological evolution and concurrent dynamic microstructure evolution of representative volumes within the deposition zone is determined by comparing depositions of hybrid feed-rods (AA6061 matrix containing an embedded tracer of AA2024). Samples were printed with and without an in-plane velocity to compare initial material feeding to steady-state deposition. Variations in initial tracer location and tool rotation rate/in-plane velocity pairs affect the final morphology, intensity of mixing, and microstructure of the deposited tracer material. The tracer material undergoes drastic mesoscopic shape evolution from millimeter-scale cylinders to long, curved micro-ribbons. There is simultaneous grain refinement in AA2024 via geometric dynamic recrystallization during initial material feeding, after which the grain size remains relatively constant at a steady-state size. The lower bound of strain is estimated based on extrusion, torsion, and shear-thinning factors.
The step-by-step mesoscopic deformation and microstructure evolution is further elucidated by characterizing depositions of hybrid feed-rods with a series of embedded tracers. The AFSD tooling is stopped quickly at the end of the deposition with a quench applied to "freeze" the sample. X-ray computed tomography reveals multiple intermediate morphologies including the progression from a cylinder to a tight spiral, to a flattened spiral shape, and to a thin disc. EBSD mapping shows that a refined microstructure is formed soon after the material leaves to tool head with areas off the centerline reaching a fully recrystallized state more quickly. The findings from this work summarize the current understanding of the link between material deformation and microstructure evolution in AFSD. Hopefully these first fundamental studies on the co-evolution of material flow and grain structure during AFSD can inspire future work, especially in the area of heterogeneous multi-material printing. / Doctor of Philosophy / Additive friction stir deposition (AFSD) is a new metal 3D printing process that uses friction to heat up and deposit materials rather than using a laser to melt the material into place. This is beneficial since it avoids problems that come from melting and solidification (e.g., porosity, hot cracking, residual stresses, columnar grains). Since AFSD is such a new technology, an understanding of some of the fundamental processing science is needed in order to predict and control the performance of the resultant parts. This is because the processing of a material affects its structure (at multiple scales, for example macro-, micro-, atomic) which then affects the properties a material will exhibit which, finally, dictates the performance of the overall part. Therefore, the purpose of this work is to explore how the feed material is transformed and deposited into the final layer after printing and to link the original processing conditions to the resultant structure. To investigate the interface between the deposited layer and the substrate, we use a simple feed-rod of one aluminum alloy (AA2024) and deposit it onto a substrate of another aluminum alloy (AA6061). To look at just one small volume within the deposited layer, we use a hybrid feed-rod that is mostly AA6061 except for small cylinders of AA2024 that are placed either in the center or on the edge of the feed-rod so that we can track the AA2024. Printing these feed-rods under different processing conditions will help us understand the connection between processing and structure. Using a characterization technique called X-ray computed tomography we can visualize a 3D representation of the final position for the AA2024 material. In order to evaluate the structure on the micro-scale, a characterization technique called electron backscatter diffraction is used to show the individual grains of our metal. The main contributions of this work are as follows: 1) a lower bound of strain is estimated for AFSD, 2) various intermediate deformation steps are captured for the tracer cylinders including a progression from cylinder to multiple spiral shapes to a thin disc to long ribbons, 3) these deformation steps are linked to different microstructures, and 4) changing the tool geometry and other processing parameters significantly alters the range of shapes and microstructures developed in the deposited material. These findings bring us closer to a fully controllable system as well as sparking some interesting areas for future research because of the complex shapes we observed. These results could lead to the customization and optimization of 3D spirals, ribbons, etc. designed for a certain application.
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