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1
Coffigniez, Marion. "Additive manufacturing of 3D architectured metallic biomaterials by robocasting". Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI007.
Abstract (sommario):
Au-delà de l'aspect de personnalisation qu'elle peut apporter au domaine médical, la fabrication additive donne aussi accès à l'élaboration de structures cellulaires. Ces structures, de porosité maîtrisée, permettent à la fois de moduler les propriétés mécaniques de l'objet, mais aussi de favoriser l'invasion cellulaire nécessaire en ingénierie tissulaire. Parmi les métaux communément utilisés en chirurgie orthopédique, les alliages de titane sont ceux présentant la rigidité la moins éloignée de celle de l'os. Cette étude porte donc sur l'élaboration de structures en Ti6-Al-4V, mais aussi en magnésium puisqu’il présente l'avantage d'être résorbable dans l'organisme. Les scaffolds sont obtenus par robocasting, procédé consistant à extruder, couche par couche une encre pâteuse constituée de poudre et de liant. Les structures sont ensuite déliantées et frittées à haute température pour atteindre leurs propriétés finales. Concernant les structures en Ti-6Al-4V, une étude paramétrique est effectuée pour évaluer les possibilités et les limites du procédé en termes de structures (et microstructures), de compositions chimiques et de propriétés mécaniques obtenues.Après optimisation, il est possible d'obtenir des pièces présentant deux niveaux de porosités interconnectées (microporosité intra-filament (interconnectée), bénéfique pour l'accroche cellulaire d'après la littérature, et macropores dessinées), gardant une limite d'élasticité spécifique supérieure à celle de l'os (105 MPa.cm³/g) et un module d'Young proche de celui de l'os (28-30 GPa). Un gradient de la porosité intra-filamentaire peut également être obtenu en faisant varier la taille de poudre au sein d’une seule et même pièce. Concernant le magnésium, un liant compatible avec la réactivité de la poudre (base éthanol) a pu être identifié et les premières étapes du procédé (impression, déliantage) sont donc tout à fait réalisables pour ce matériau. Toutefois, le frittage conventionnel du magnésium (pur) s'avère compliqué du fait de sa réactivité. Des alternatives de frittage sont donc étudiées (frittage en phase liquide, SPS)Beyond the personalisation aspect that it can bring to the medical field, additive manufacturing also gives access to the elaboration of cellular structures. These structures, with controlled porosity, make it possible both to modulate the mechanical properties of the object and to promote the cellular invasion necessary in tissue engineering. Among the metals commonly used in orthopaedic surgery, titanium alloys are those with the rigidity least distant from that of bone. This study therefore focuses on the development of structures made of Ti6-Al-4V, but also of magnesium since it has the advantage of being resorbable in the body. The scaffolds are obtained by robocasting, a process consisting of extruding, layer by layer, a pasty ink made up of powder and binder. The structures have then to be debinded and sintered at high temperature to achieve their final properties. For Ti-6Al-4V structures, a parametric study is carried out to evaluate the possibilities and limits of the process in terms of structures (and microstructures), chemical compositions and mechanical properties obtained. After optimisation, it is possible to obtain parts with two levels of interconnected porosities (intra-filament (interconnected) microporosity, beneficial for cell adhesion according to the literature, and drawn macropores), keeping a specific yield strength higher than that of bone (105 MPa.cm³/g) and a Young's modulus close to that of bone (28-30 GPa). An intra-filament porosity gradient can also be obtained by varying the powder size within a single part. Concerning magnesium, a binder compatible with the reactivity of the powder (ethanol base) has been identified and the first steps of the process (printing, debinding) are therefore quite feasible for this material. However, conventional sintering of (pure) magnesium is complicated by its reactivity. Alternative sintering methods are therefore being investigated (liquid phase sintering, Spark Plasma Sintering)
2
Karmakar, Mattias. "Additive Manufacturing Stainless Steel for Space Application". Thesis, Luleå tekniska universitet, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72901.
3
El, Mouhib Sabrina. "Effect of Stainless Steel Additive Manufacturing On Heat Conductivity and Urea Deposition". Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287314.
Abstract (sommario):
Hydroforming is the manufacturing process that Scania uses to produce exhaust pipes with complex shape and high durability. Selective Laser Melting is the process used by designers to print prototype pipes and perform emissions tests before mass production. Results from previous tests at Scania showed superior performance of 3D printed pipes compared to hydroformed components during emissions test as the 3D printed pipes were able to transfer heat faster than hydroformed pipes. To understand the reason behind this mismatch, the effect of selective laser melting parameters on energy density, relative density, grain size and thermal conductivity are investigated. These properties have direct impact on heat transfer. Ten samples were fabricated using the same laser power and layer thickness but different combinations of scanning speed and hatch distance. Samples were then subject to microstructural analysis using an optical microscope and average grain size measurement using image analysis software called Imagej. The density of each sample was measured using the Archimedes method. Moderate correlation is found between energy density and relative density. No ranking of the selective laser melting parameters with respect to forming the highest density was achieved because of the high uncertainties involved with the density measurement technique. Thermal conductivity was measured us- ing the one dimensional heat flow equation with an appropriate experimental set up. Thermal conductivity seems to be more influenced by relative density and direction of printing layers than the energy density and grain size. This conclusion is not statistically significant due to high uncertainty involved in the measurement of thermal conductivity. More advanced and accurate tech- nologies need to be used in the future to measure both density and thermal conductivity in order to find the most suitable selective laser melting parameters for Scania’s prototype pipes. The findings of this research can be used as a foundation for future research related to urea deposition on 3D printed pipes.Hydroforming är den tillverkningsprocess Scania använder för att producera avgasrör som har en komplex form och hög hållbarhet. Selektiv lasersmältning är den process som används av konstruktörer för att skriva ut prototyprör och utföra utsläppstester före massproduktion. Resultat från tidigare utsläppstes- ter på Scania visade en överlägsen prestanda för 3D-tryckta rör jämfört med hydroformade komponenter, eftersom 3D-tryckta rör kunde överföra värme snabbare än hydroformade rör. För att förstå orsaken bakom denna skillnad undersöks effekten av selektiva lasersmältningsparametrar som energitäthet, relativ densitet, kornstorlek och värmeledningsförmåga. Dessa egenskaper har direkt inverkan på värmeöverföringen. 10 prover tillverkades med samma laserkraft och skikttjocklek, men med olika kombinationer av skanningshastighet och kläckavstånd. Proverna utsattes sedan för en mikrostrukturell analys med hjälp av ett optiskt mikroskop, samt genomsnittlig kornstorleksmätning med hjälp av bildanalysprogramvaran Imagej. Densiteten för varje prov mättes med Archimedesmetoden. Måttlig korrelation kunde identifieras mellan energitätheten och relativ densitet. Ingen rangordning av de selektiva lasersmältningsparametrarna med avseende på bildning av den högsta densiteten uppnåddes på grund av de höga osäkerhetsfaktorer som är involverade i densitetsmättekniken. Värmeledningsförmågan mättes med hjälp av den endimensionella värmeflödesekvationen, med en lämplig experimentell uppställning. Värmeledningsförmågan tycks påverkas mer av tryckskiktens relativa densitet och riktning än energidensiteten och kornstorleken. Denna slutsats är inte statistiskt signifikant på grund av hög osäkerhet i mätningen av värmeledningsförmåga. Mer avancerade och noggranna teknologier måste användas i framtiden för att mäta både densitet och värmeledningsförmåga, för att hitta de mest lämpliga selektiva lasersmältningsparametrarna för Scanias prototyprör.
4
Gullapalli, Vikranth. "Study of Metal Whiskers Growth and Mitigation Technique Using Additive Manufacturing". Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804972/.
Abstract (sommario):
For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure.Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.
5
Zavala, Arredondo Miguel Angel. "Diode area melting : use of high power diode lasers in additive manufacturing of metallic components". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18953/.
Abstract (sommario):
Additive manufacturing processes have been developed to a stage where they can now be used to manufacture net-shape high-value components. Selective Laser Melting (SLM) comprises of either a single or multiple deflected high energy fibre laser source(s) (e.g. 200 – 400 W each) to raster scan, melt and fuse layers of metallic powdered feedstock. The beam(s) is(are) deflected by a Scanning Galvo Mirror System and an F-theta lens is used to provide a flat field at the image plane of the scanning system. However, this deflected laser raster scanning methodology is high cost (addition of multiple high-power deflected lasers in SLM for increase productivity can suffer penalties of ~£170K for each additional laser), energy inefficient (wall-plug efficiency of typical SLM fibre laser sources ~50 % [1]) and encounters significant limitations on output productivity due to the rate of feedstock melting (e.g. typical theoretical build rate of SLM of stainless steel < 2.8 mm3/s (< 10cm3/min) [2]). This work details the development of a new additive manufacturing process known as Diode Area Melting (DAM) featuring multiple high efficient laser sources (i.e. > 60 % wall-plug efficiency [1]) with scalability potential (< £100 penalty per additional laser beam for increase productivity). This process utilises customised architectural arrays of low power laser diode emitters (i.e. ~5W laser power) for high speed parallel processing (theoretical build rate of scaled DAM of stainless steel > 2.8 mm3/s (> 10cm3/min)) of metallic feedstock. Individually addressable diode emitters are used to selectively melt feedstock from a pre-laid powder bed. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials [3][4]. The melting capabilities of the DAM process were tested for low melting point eutectic BiZn2.7 elemental powders, AlSi12 and higher temperature pre-alloyed 17-4 and 316L stainless steel powders. The process was shown to be capable of fabricating controllable geometric features with evidence of complete melting and fusion between multiple powder layers. This investigation presents a parametric analysis of the DAM process, identifying the effect of powder characteristics, laser beam profile, laser power and scan speed on the porosity of a single layer sample. Also presented is the effect of process energy density on melt pool depth (irradiated thermal energy penetration capable of achieving melting) on 316L stainless steel powder. An analysis of the density and the melt depth fraction of single layers is presented in order to identify the conditions that lead to the fabrication of fully dense DAM parts. Energy densities in excess of 86 J/mm3 were theorised as sufficient to enable processing of fully dense layers. Finally, this investigation presents the first work modelling the DAM process, detailing the unique thermal profiles experienced with the laser processed powder bed. Process optimisation is improved through modelling thermal temperature distribution, targeting processing conditions inducing full melting for variable powder layer thickness. In this work the developed thermal model simulates the processing of 316L stainless steel and is validated with experimental trials. Key findings that have been identified in the present research include the following: • Edge emitting diode laser modules featuring multiple ~5 W emitters, can be used directly in AM of metallic components. • Typical 808 nm diode lasers wavelength enables high laser absorption mechanisms in a metal powder-bed based AM process, which in turn allows the use of lower laser power (< 5 W) than the conventionally used in SLM (100-400 W). • Temperatures in excess of 1450 ºC can be reached in metallic powder beds (stainless steel) with < 5 W diode-laser spots using appropriate optical mechanisms to collimate and focus the low-quality beam (27º and 7º divergence in the fast and slow axis respectively) down to < 250 µm melting spots. • It has been identified the ability to near-net shape and process material with melt temperatures in excess of 1450 ºC (i.e. stainless steel powder) using multiple individually addressable and non-deflected low power diode laser beams in order to scan in parallel, selectively melting material from a powder bed. • DAM process parameters including laser beam profile (i.e. spot spacing and spot dimensions), particle size distribution (emissivity and conductivity of the powder), laser power and scan speed affect the porosity and melt-pool uniformity of DAM components. • An energy density of 86 J/mm3 can be theorised as the minimum required for fully dense DAM (stainless steel) components. • Effective melt area in DAM can be 6.67 % in excess of the actual spots size (i.e. 4.75 mm laser beam width has an effective melt width of 5.067 mm). • Temperature gradients and cooling rates during DAM processing of metallic feedstock are similar to optimised pre-heated SLM mechanisms with low residual stress formation.
6
Hari, Vignesh. "Evaluating spreadability of metallic powders for powder bed fusion processes". Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283544.
Abstract (sommario):
Additive manufacturing technologies are widely used in aerospace, space, and turbine industries. Parts can be manufactured directly by selectively adding materials layer-by-layer. A key aspect that is critical to the quality of the final component being manufactured is the powder characteristics. The prevailing powder characterisation techniques help in predicting the flowability of powders but do not relate to the spreading nature of the powder. To create high-quality thin layers of metal powder, it is essential to understand powder spreadability in powder bed-based additive manufacturing processes. The objective of this study was to create spreadability metrics using image analysis, mass analysis, and density analysis. A lab-scale experimental setup was constructed to replicate the powder bed-based additive manufacturing process. The impact of spreading speed and layer thickness on five different steel powders were studied using the suggested metrics. The metrics obtained powder rheometry and revolution powder analysis. The flowability parameters were compared to the spreadability analysis. Image analysis was shown to be efficient to predict the spreading nature of the powder when the processing parameters are varied. One metric, the convex hull ratio, was found to be high for free-flowing powders. The spread area of free-flowing powders was higher than the powders with poor flow properties. A mass-based analysis procedure shows that the ratio of mass deposited to the theoretical mass fluctuated in a systematic manner as a function of testing parameters and for different powders, suggesting that the mass analysis might be another potential metric to assess spreadability. The density-based analysis was effective in differentiating the layer density of different powders under various experimental conditions. It is expected that the proposed metrics will be a beginning for developing further characterisation techniques. For example, the layer thickness could be studied by creating a homogenous layer. We anticipate these metrics to be used to develop standardisation techniques for defining and quantifying powder spreadability, and thereby improve quality ofadditive manufacturing processes.Additiv tillverkning är teknologier som har stor uträckning inom flyg-, rymd och turbin industrier. Delar kan bli tillverkade direkt genom att lagervis addera material på varandra. En nyckelaspekt som är kritisk till kvalitén av den slutgiltiga komponenten är egenskaperna hos pulvret. De allmänna teknikerna för pulverkarakterisering hjälper till att förutspå flytförmågan hos pulver men relaterar ej till dess spridningsförmåga. För att kunna skapa högkvalitativa skikt av metallpulver är det nödvändigt att förstå pulvrets spridningsförmåga inom pulverbädds baserade additiva tillverkningsprocesser. Målet med denna studie var att skapa ett mått för spridningsförmågan genom bild- och massanalys. Ett experimentellt upplägg i labbskala konstruerades för att efterlikna en pulverbädds baserad additiv tillverkningsprocess. Effekten av bladets hastighet och lagrets tjocklek på fem olika pulver studerades genom användandet av de föreslagna mätetalen. De framtagna mätetalen jämfördes sedan med existerande pulver karakteriseringsmetoder såsom FT-4 Rheometer och pulver analys med hjälp av roterande trumma. Slutligen så jämförs flytbarhets parametrarna med spridbarhets mätetalen. Det visar sig att bildanalysen är tillräckligt bra på att förutspå spridningsförmågan hos pulvret när processparametrarna låtes vara varierande. Mer specifikt så var förhållandet mellan pulvrets yta och det konvexa höljet stort för pulver som visar bra spridning. De framtagna procent värden från massanalysdiagrammen fluktuerar vid olika processparametrar hos de olika pulvren, vilket kan betyda att massanalys kan vara ett potentiellt sätt för att mätta spridningsförmågan hos pulver. Det är förväntat att dessa föreslagna mätetal kommer vara början för utveckling av ytterligare karakteriseringstekniker. Till exempel, för att studera densiteten och tjockleken hos ett lager skulle man kunna skapa homogena lager. Vi förutser att dessa mätetal kommer att bli använda för att skapa standardiseringstekniker för att definiera och kvantifiera spridningsförmågan hos ett pulver och genom detta förbättra kvaliteten av den additiva tillverkningsprocessen.
7
Jönsson, David, e Mir Kevci. "Geometrical accuracy of metallic objects produced with Additive or Subtractive Manufacturing: a comparative in-vitro study". Thesis, Malmö högskola, Odontologiska fakulteten (OD), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-19934.
Abstract (sommario):
Syftet: Utvärdera produktionstolerans av objekt som producerats genom additiv framställningsteknik (AF) för användning inom tandvård, samt att jämföra denna teknik med subtraktiv framställningsteknik (SF) genom reverse engineering.Material och metod: Tio exemplar av två olika geometriska objekt framställdes från fem olika AF maskiner och en SF maskin. Objekt A efterliknar ett inlay, medan objekt B återspeglar en modell av en fyrledsbro. Alla objekt delades in i olika mätled; X, Y och Z. Mätningarna utfördes med validerade och kalibrerade instrument. Linjära avstånd mättes med ett digitalt skjutmått och hörnradie samt vinklar mättes med ett digitalt mikroskop.Resultat: Vare sig additiv eller subtraktiv framställning uppvisade en perfekt matchning till CAD-filen med hänsyn till de parametrar som utvärderades i denna studie. Standardavvikelsen gällande linjära mätningar för subtraktiv framställning uppvisade konsekventa resultat i alla led, med undantag för X- och Y-led för objektet A och i Y-led för objekt B. Samtliga additiva tillverkningsgrupper hade en konsekvent standardavvikelse i X- och Y-led, men inte i Z-led. Med avseende på hörnradiemätningar, hade SF gruppen i överlag bättre produktionsnoggrannhet för både objekt A och B medan AM grupperna var mindre noggranna.Konklusion: Med hänsyn till begränsningarna med denna in vitro studie, stödjer resultat hypotesen, med hänsyn till att AF hade en bättre förmåga att återskapa komplexa och små geometrier jämfört med SF. Samtidigt identifierades en bättre reproducerbarhet hos SF gällande enkla geometrier och linjära avstånd. Vidare studier krävs för att bekräfta dessa resultat.Purpose: To evaluate the production tolerance of objects produced by additive manufacturing systems (AM) for usage in dentistry and to compare with subtractive manufacturing system (SM) through reverse engineering. Materials and methods: Ten specimens of two geometrical objects were produced by five different AM machines and one SM machine. Object A mimics an inlay-shaped object, meanwhile object B reflects a four-unit bridge model. All the objects were divided into different measuring-axis; X, Y and Z. Measurements were performed with validated and calibrated equipment. Linear distances were measured with a digital calliper while corner radius and angle were measured with a digital microscope. Results: None of the additive manufacturing or subtractive manufacturing groups presented a perfect match to the CAD-file regarding all parameters included in present study. Considering linear measurements, the standard deviation for subtractive manufacturing group were consistent in all axis, except for X- and Y-axis in object A and Y-axis for object B. Meanwhile additive manufacturing groups had a consistent standard deviation in X- and Y- axis but not in Z-axis. Regarding corner radius measurements, SM group overall had the best accuracy for both object A and B comparing to AM groups. Conclusion: Within the limitations of this in vitro study, results support the hypothesis, considering AM had preferable capability to re-create complex and small geometry compare to SM. Meanwhile, SM were superior producing simple geometry and linear distances. Further studies are required to confirm these results.
8
Sjöström, Julia. "Linkage of Macro- and Micro-scale Modelling Tools for Additive Manufacturing". Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283603.
Abstract (sommario):
Additive manufacturing methods for steel are competing against commercial production in an increasing pace. The geometry freedom together with the high strength and toughness due to extreme cooling rates make this method viable to use for high-performance components. The desirable material properties originate from the ultrafine grain structures. The production is often followed by a post hardening heat treatment to induce precipitation of other phases. The printing process does however bring several challenges such as cracking, pore formation, inclusions, residual stresses and distortions. It is therefore important to be able to predict the properties such as temperature evolution and residual stresses of the resulting part in order to avoid time consuming trial-and-error and unnecessary material waste. In order to link different parts and length scales of the process, the integrated computational materials engineering framework can be used where linkage tools couples results of different length scales. 18Ni300 maraging steel is a material that has been used extensively to produce parts by additive manufacturing, but there is still a wide scope for optimising the process and properties. In this thesis, the integrated computational materials engineering inspired framework is applied to link the process to the microstructure, which dictates the properties. Temperature evolution strongly influences the material properties, residual stresses and distortion in additive manufacturing. Therefore, simulations of temperature evolution for a selective laser melted 18Ni300 maraging steel have been performed by Simufact Additive and linked with the microstructure prediction tools in Thermo-Calc and DICTRA. Various printing parameters have been examined and resulting temperatures, cooling rates, segregations and martensitic start temperatures compared for different locations of the build part. Additionally, residual stresses and distortions were investigated in Simufact. It was found that higher laser energy density caused increased temperatures and cooling rates which generally created larger segregations of alloying elements and lower martensitic start temperatures at the intercellular region. There is however an impact from cooling rate and temperature independent of the energy density which makes energy density not an individual defining parameter for the segregations. By decreasing the baseplate temperature, lower temperatures below the martensitic start temperature were reached, enhancing martensite transformation. Primary dendrite arm spacing calculations were used to validate the cooling rates. The cell size corresponded well to literature of <1 μm. Distortions and residual stresses were very small. The calibration was based according to literature and need experimental values to be validated. The integrated framework demonstrated in this thesis provides an insight into the expected properties of the additively manufactured part which can decrease and replace trial-and-error methods.dditiva tillverkningsmetoder för stål tävlar mot kommersiell produktion i en ökande takt. Geometrifriheten tillsammans med hög styrka och slagseghet på grund av extrema kylhastigheter gör den här metoden intressant att använda för högpresterande komponenter. De önskvärda materialegenskaperna härstammar från den ultrafina mikrostrukturen. Processen följs ofta av en värmebehandlande härdning för att inducera utskiljningar av andra faser. Printing processen innebär dock flertalet utmaningar som exempelvis sprickbildning, porer, inneslutningar, restspänningar och förvrängningar. Det är därför intressant och viktigt att förutspå egenskaper såsom temperaturutveckling och restspänningar av den slutgiltiga komponenten för att minska tidskrävande ”trial-and-error” och onödigt materialsvin. För att länka ihop olika delar och längdskalor av processen kan ”the integrated computational materials engineering” strukturen användas där länkverktyg kopplar ihop resultat av olika längdskalor. 18Ni300 maraging stål är ett material som har använts till additivt tillverkade produkter i hög utsträckning men det finns fortfarande mycket utrymme för optimering av processen och egenskaperna. I den här avhandlingen, den ”integrated computational materials engineering” inspirerade tillvägagångssättet används för att länka processen med mikrostrukturen, vilken bestämmer egenskaperna. Temperaturutveckling påverkar kraftigt materialegenskaper, restspänningar och deformation vid additiv tillverkning. Förutsägelse av temperatur för ett selektivt lasersmält 18Ni300 stål har därför genomförts i Simufact Additive och länkats med mikrostruktursförutsägande redskapen Thermo-Calc och DICTRA. Olika maskinparametrar har undersökts och efterföljande temperaturer, kylhastigheter, segregeringar och martensitiska starttemperaturer jämförts för olika delar av geometrin. Tilläggningsvis var även restspänningar och deformationer undersökta i Simufact. Det konstaterades att högre energidensitet för lasern orsakade högre temperaturer och kylhastighet vilket generellt skapade mer segregeringar av legeringsämnen och lägre martensitisk starttemperatur i de intercellulära områdena. Det är däremot en gemensam påverkan av kylhastighet och temperatur vilket gör att energidensitet inte är den enskilda bestämmande parametern över segregeringarna. Genom att sänka temperaturen på basplattan uppnåddes lägre temperaturer under den martensitiska starttemperaturen vilket förenklar den martensistiska omvandlingen. Beräkningar av primär dendritisk armlängd användes för att validera kylhastigheterna. Cellstorleken överensstämde bra med litteraturen på <1 μm. Deformationer och restspänningar var väldigt små. Kalibreringarna baserades på litteraturvärden och kräver experimentella värden för att valideras. Den integrerade strukturen som demonstreras i den här avhandlingen förser en insikt i de förväntade egenskaperna av en additivt tillverkad del vilket kan minska och ersätta ”trial-and-error” metoder.
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Corona, Galvan Luis. "Prototypage rapide de pièces en acier : étude du dépôt de matière et d'énergie lors de la fusion à l'arc d'un fil par le procédé MIG-CMT". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS062/document.
Abstract (sommario):
Un banc d’essai spécialement dédié à la fabrication additive par une nouvelle technologie basée sur la fusion à l’arc électrique d’un fil métallique a été développé. Le procédé utilise une source de soudage à l’arc appelée Cold Metal Transfer (CMT) pour assurer la fusion contrôlée d’un fil métallique et le dépôt de gouttelettes de métal liquide, afin de produire par la superposition de cordons des pièces mécaniques. La technologie développée a été employée pour fabriquer des éprouvettes à partir d’un fil en acier faiblement alliés. L’influence des nombreux paramètres contrôlant la source de soudage à l’arc sur les mécanismes de fusion du fil et de transfert des gouttelettes de métal fondu pour former les cordons a été étudiée. Les cycles de fusion-transfert de métal liquide ont été analysés en particulier au regard des énergies générées durant chacune des phases du cycle. Cette connaissance a permis de trouver des réglages du procédé permettant d’accroître le taux de dépôt de métal en comparaison des réglages standards préenregistrés dans le microprocesseur du générateur de soudage CMT. Des murs constitués par la superposition d’un grand nombre de cordons ont ensuite été réalisés, et l’influence de l’ajout de nombreuses couches sur la géométrie des dépôts discutée. Finalement, une méthode de contrôle en ligne du procédé, basée sur le principe des cartes de contrôle, a été développée. Une étude approfondie des formes d’onde d’intensité et de tension représentatives du cycle de fusion/transfert avec le procédé CMT a permis d’identifier les caractéristiques les plus pertinentes pour détecter, à partir d’une carte de contrôle, une dérive du procédé pouvant conduire à l’apparition de défauts géométriquesA test bench specially dedicated to additive manufacturing by a new technology based on the electric arc melting of a metallic wire has been developed. This technology uses an electric arc welding process called Cold Metal Transfer (CMT) as energy source to ensure the controlled melting of the wire and the deposition of liquid metal droplets to produce mechanical parts by superposing weld beads. The developed technology was used to make specimens from a low alloyed steel wire. The influence of the many parameters controlling the arc welding source on the mechanism of wire melting and transfer of molten metal droplets to form weld beads was studied. The melting-transfer cycles of liquid metal were analyzed in particular with special interest in the energies generated during each of the cycle phases. This knowledge has made possible to find different process settings for increasing the metal deposition rate compared to the pre-recorded standard settings in the microprocessor of the CMT welding generator. Walls consisting of the superposition of a large number of weld beads were then made, and the influence of the addition of many layers on the geometry of the deposits were discussed. Finally, a method of online control of the process, based on the principle of control charts, has been developed. A detailed study of the representative waveforms of current and voltage of the melting / transfer cycle with the CMT process has allowed to identify the most relevant characteristics for detecting, from a control chart, a deviation on the process that may lead to the appearance of geometrical defects
10
Boissier, Mathilde. "Coupling structural optimization and trajectory optimization methods in additive manufacturing". Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX084.
Abstract (sommario):
Cette thèse porte sur l’optimisation des trajectoires de lasage pour la fabrication additive sur lit de poudre, ainsi que leur lien avec la géométrie de la pièce à construire. L’état de l’art est principalement constitué par des trajectoires basées sur des motifs, dont l’impact sur les propriétés mécaniques des objets finaux est quantifié. Cependant, peu d’analyses permettent de relier leur pertinence à la forme de la pièce elle-même. Nous proposons dans ce travail une approche systématique visant à optimiser la trajectoire sans restriction a priori. Le problème d’optimisation consiste à fusionner la structure en évitant de surchauffer (ce qui induirait des contraintes résiduelles) tout en minimisant le temps de fabrication. L’équation d’état est donc l’équation de la chaleur, dont le terme source dépend de la trajectoire. Deux modèles 2-d sont proposés pour contrôler la température : l’un transitoire et le second stationnaire (pas de dépendance en temps). Basés sur des techniques d’optimisation de forme pour le stationnaire et sur des outils de contrôle pour le transitoire, des algorithmes d’optimisation sont développés. Les applications numériques qui en découlent permettent une analyse critique des différents choix effectués. Afin de laisser plus de liberté dans la conception, l’algorithme stationnaire est adapté à la modification du nombre de composantes connexes de la trajectoire lors de l’optimisation. Deux méthodes sont comparées. Dans la première, la puissance de la source est ajoutée aux variables d’optimisation et un algorithme impliquant une relaxation-pénalisation et un contrôle de la variation totale est proposé. Dans la seconde, la notion de dérivation topologique est adaptée à la source. Enfin, dans le cadre stationnaire, nous détaillons le couplage de l’optimisation de la forme de la pièce, pour améliorer ses performances mécaniques, et de la trajectoire de lasage. Ce problème multiphysique ouvre des perspectives d'applications et de généralisations futuresThis work investigates path planning optimization for powder bed fusion additive manufacturing processes, and relates them to the design of the built part. The state of the art mainly studies trajectories based on existing patterns and, besides their mechanical evaluation, their relevance has not been related to the object’s shape. We propose in this work a systematic approach to optimize the path without any a priori restriction. The typical optimization problem is to melt the desired structure, without over-heating (to avoid thermally induced residual stresses) and possibly with a minimal path length. The state equation is the heat equation with a source term depending on the scanning path. Two physical 2-d models are proposed, involving temperature constraint: a transient and a steady state one (in which time dependence is removed). Based on shape optimization for the steady state model and control for the transient model, path optimization algorithms are developed. Numerical results are then performed allowing a critical assessment of the choices we made. To increase the path design freedom, we modify the steady state algorithm to introduce path splits. Two methods are compared. In the first one, the source power is added to the optimization variables and an algorithm mixing relaxation-penalization techniques and the control of the total variation is set. In a second method, notion of topological derivative are applied to the path to cleverly remove and add pieces. eventually, in the steady state, we conduct a concurrent optimization of the part’s shape and of the scanning path. This multiphysics optimization problem raises perspectives gathering direct applications and future generalizations
11
Hernandez, Ludwing A. "Integration of Ultrasonic Consolidation and Direct-Write to Fabricate an Embedded Electrical System Within a Metallic Enclosure". DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/780.
Abstract (sommario):
A research project was undertaken to integrate Ultrasonic Consolitation (UC) and Direct-Write (DW) technologies into a single apparatus to fabricate embedded electrical systems within an ultrasonically consolidated metallic enclosure. Process and design guidelines were developed after performing fundamental research on the operational capabilities of the implemented system. In order to develop such guidelines, numerous tests were performed on both UC and DW. The results from those tests, as well as the design and process guidelines for the fabrication of an embedded touch switch, can be used as a base for future research and experimentation on the UC-DW apparatus. The successful fabrication of an embedded touch switch proves the validity of the described design and process parameters and demonstrates the usefulness of this integration.
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Carlsson, Rebecca. "Comparison of turning blades produced by a conventional- and additive manufacturing method". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-69032.
Abstract (sommario):
Additive manufacturing has developed radical through the years. Sandvik has invested in the area by building a center specific for additive manufacturing. Due to problems with the material- and product properties and high production costs no products have been used with additive manufacturing method. These aspects have improved over the years and therefore the master thesis was made with an objective: to compare two different produced blades with focus on the aspects of material- and product properties and production costs. One of the blades was produced through additive manufacturing (AM) and the other blade was produced in today’s production at Sandvik Coromant in Gimo. If the blade can be produced through AM there is a possibility to lower the production costs and improve the degree of design freedom. The material that will be used is SS2230 (50CrV4) which are used in conventionally produced blades and 1.2709 which are used in AM produced blades. The investigation consisted of five different tests (flow rate, pressure force, vibration, fatigue and keyhole wear) and a study on production aspects with focus on value stream mapping, investments and production costs. The main objective in the result was to compare each test between the two different produced blades, not to investigate the optimal value. Therefore, was the test designed to have continuity with as small deviation as possible between the tests. This resulted in choosing values which were not optimal for the blades but focused on continuity and deviation. The coolant channels flow rate improved with 35% on the AM produced blades but pressure force, fatigue and keyhole wear resistance did not deviate much from conventionally produced blades. Fatigue tests were made twice with two different inserts because the result from the first test differentiated too much from the expected results on both blades. Production costs will be higher with AM but on a long-term may an investment improve the degree of design freedom on a product and a possibility to produce towards costumer (just in time). This will need an expensive investment with a bigger perspective on the timeframe. The value of the product may increase but the production costs will increase too.
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Samarjy, Ramiz Saeed Matti. "Interaction mechanisms for a laser-induced metallic boiling front". Doctoral thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65281.
Abstract (sommario):
This thesis is about fundamental interaction mechanisms of laser remote fusion cutting, RFC, which is based on the formation of a quasi-stationary laser-induced boiling front that causes drop ejection, preferably downwards. Laser cutting of metals, invented in 1967, has developed from a niche to a well established high quality cutting technique in the manufacturing industry. Usually a gas jet is employed concentric to the laser beam, to eject the molten metal. One technique option, interesting though hardly applied yet because of usually low quality and speed, is remote laser cutting. Two techniques are distinguished, remote ablation cutting, grooving down through a sheet, layer-by-layer, and the here addressed remote fusion cutting, by a single pass through the sheet. For the latter, the ablation pressure from laser-induced boiling at the cutting front continuously accelerates and ejects the melt downwards. Advantages of remote laser cutting, facilitated by high brilliance lasers during the last decade, are the possibility of a larger working distance along with the avoidance of cutting gas and of a gas jet nozzle. The review paper of the thesis surveys different laser remote cutting techniques, including their modelling, as well as the transition to keyhole welding, owing to similarities particularly from the boiling front and from root spatter ejection. The six Papers I-VI that compose the thesis address fundamental mechanisms of laser remote fusion cutting, theoretically and experimentally. In Paper I a simplified mathematical model of the RFC cutting front enables to estimate the geometrical and energetic conditions of the process. By evidence and post-modelling from high speed imaging, HSI, the simplified smooth cutting front model is developed further to a wavy topology in Paper III, for more sophisticated absorption analysis. As a systematic support, Paper II categorizes and analyses for the first time the different wavy topologies observed at the front, from HSI. The melt dynamics induced by a pulsed laser beam was studied in Paper IV, again from HSI. Apart from other interesting transient melt phenomena it was demonstrated that the ablation pressure can push the melt to a certain pending position during the laser pulse while the melt retreats by surface tension during the pulse break. To engage remote fusion cutting with additive manufacturing, Paper V introduces a novel technique where the drops ejected from RFC are transferred to a substrate, about a centimetre underneath, on which a continuous track forms. This technique can even be applied as an efficient recycling approach. In Paper VI a variant of the technique is presented, to develop a boiling front along the edge of a metal sheet from which the drop transfer takes place, in a different manner. This enables to systematically machine-off the entire sheet, which can be converted to a new shape and product. Summarizing, the thesis provides a variety of analysis of fundamental mechanisms of a laser-induced boiling front that bear a certain simplicity and in turn controllability, of interest for established as well as for new applications, in manufacturing and in other sectors, including remote fusion cutting.
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Myers, Kyle M. "Structure-Property Relationship of Binder Jetted Fused Silica Preforms to Manufacture Ceramic-Metallic Interpenetrating Phase Composites". Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1464089607.
15
Xu, Jinghao. "Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing". Licentiate thesis, Linköpings universitet, Konstruktionsmaterial, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-173042.
Abstract (sommario):
Nickel-based superalloys, an alloy system bases on nickel as the matrix element with the addition of up to 10 more alloying elements including chromium, aluminum, cobalt, tungsten, molybdenum, titanium, and so on. Through the development and improvement of nickel-based superalloys in the past century, they are well proved to show excellent performance at the elevated service temperature. Owing to the combination of extraordinary high-temperature mechanical properties, such as monotonic and cyclic deformation resistance, fatigue crack propagation resistance; and high-temperature chemical properties, such as corrosion and oxidation resistance, phase stability, nickel-based superalloys are widely used in the critical hot-section components in aerospace and energy generation industries. The success of nickel-based superalloy systems attributes to both the well-tailored microstructures with the assistance of carefully doped alloying elements, and the intently developed manufacturing processes. The microstructure of the modern nickel-based superalloys consists of a two-phase configuration: the intermetallic precipitates (Ni,Co)3(Al,Ti,Ta) known as γ′ phase dispersed into the austenite γ matrix, which is firstly introduced in the 1940s. The recently developed additive manufacturing (AM) techniques, acting as the disruptive manufacturing process, offers a new avenue for producing the nickel-based superalloy components with complicated geometries. However, γ′ strengthened nickel-based superalloys always suffer from the micro-cracking during the AM process, which is barely eliminated by the process optimization. On this basis, the new compositions of γ′ strengthened nickel-based superalloy adapted to the AM process are of great interest and significance. This study sought to design novel γ′ strengthened nickel-based superalloys readily for AM process with limited cracking susceptibility, based on the understanding of the cracking mechanisms. A two-parameter model is developed to predict the additive manufacturability for any given composition of a nickel-based superalloy. One materials index is derived from the comparison of the deformation-resistant capacity between dendritic and interdendritic regions, while another index is derived from the difference of heat resistant capacity of these two spaces. By plotting the additive manufacturability diagram, the superalloys family can be categorized into the easy-to-weld, fairly-weldable, and non-weldable regime with the good agreement of the existed knowledge. To design a novel superalloy, a Cr-Co-Mo-W-Al-Ti-Ta-Nb-Fe-Ni alloy family is proposed containing 921,600 composition recipes in total. Through the examination of additive manufacturability, undesired phase formation propensity, and the precipitation fraction, one composition of superalloy, MAD542, out of the 921,600 candidates is selected. Validation of additive manufacturability of MAD542 is carried out by laser powder bed fusion (LPBF). By optimizing the LPBF process parameters, the crack-free MAD542 part is achieved. In addition, the MAD542 superalloy shows great resistance to the post-processing treatment-induced cracking. During the post-processing treatment, extensive annealing twins are promoted to achieve the recrystallization microstructure, ensuring the rapid reduction of stored energy. After ageing treatment, up to 60-65% volume fraction of γ′ precipitates are developed, indicating the huge potential of γ′ formation. Examined by the high-temperature slow strain rate tensile and constant loading creep testing, the MAD542 superalloy shows superior strength than the LPBF processed and hot isostatic pressed plus heat-treated IN738LC superalloy. While the low ductility of MAD542 is existed, which is expected to be improved by modifying the post-processing treatment scenarios and by the adjusting building direction in the following stages of the Ph.D. research. MAD542 superalloy so far shows both good additive manufacturability and mechanical potentials. Additionally, the results in this study will contribute to a novel paradigm for alloy design and encourage more γ′-strengthened nickel-based superalloys tailored for AM processes in the future.Additional funding agencies: Agora Materiae Graduate School for multidisiplinary PhD students at Linköping University, and Stiftelsen Axel Hultgren.
16
Svensson, Marcus. "Selection of a product component for topology optimization and additive manufacturing". Thesis, Jönköping University, JTH, Industriell produktutveckling, produktion och design, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-52791.
Abstract (sommario):
This is a master thesis research on how to select the right components in a product, considering reducing the weight with topology optimization (TO) and adaption for additive manufacturing (AM). It is well established that manufacturing of complex structures can be achieved with AM, the possibility of integrating assembled components and improve features will therefore be investigated. The new component structure must still withstand the loads that it is subjected to during usage, to not permanently deform or break. In this research the studied product was a handheld Husqvarna chainsaw. Initially a feasibility study was conducted, where the product was disassembled and physically investigated for potential component cases. Additional knowledge was gathered with one semi structured interview per case, with experienced design engineers. Followed by one semi structured interview with AM experts, regarding available AM technique and similar material. Selection of case to continue with was based on the interviews information and Pughs decision matrix, with weighted criterions. TO were used for finding the optimal material distribution. The new component design was analyzed with linear finite element analysis to fulfill both the component and material stress requirements. Component orientation and support structure for AM was analyzed with computer aided engineering software. This resulted with integrating thirteen components for the engines cylinder into one component. The new design resulted in a weight reduction of 31%, while utilizing only 57% of the allowed stress limit. Also, the first 23 natural frequencies were improved with a new type of cooling fin structure, with an increased area of 15%. These results encourage the thesis workflow methodology usage for other products. In conclusion the established workflow of methods resulted in selecting a suitable case for integrating components with feature improvement and adaption of the new design with TO for AM, to reduce the weight.
17
Beiker, Kair Alexandros, e Konstantinos Sofos. "Additive Manufacturing and Production of Metallic Parts in Automotive Industry : A Case Study on Technical, Economic and Environmental Sustainability Aspects". Thesis, KTH, Industriell produktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149669.
Abstract (sommario):
Additive Manufacturing (AM) comprises a family of different technologies that build up parts by adding materials layer by layer at a time based on a digital 3D solid model. After thirty years of development, AM has become a mainstream manufacturing process with more materials and new technologies involved in this process. Undoubtedly, the most dramatic and challenging development of group of technologies has been the printing of metals. Nowadays, the use of AM for the production of parts for final products continues to grow. Organizations around the world are successfully applying the technology to the production of finished goods. AM allows design optimization and produces customized parts on-demand with almost similar material properties with the conventional manufactured parts. It does not require the use of coolants, fixtures, cutting tools and other assisting resources. The advantages of AM over conventional manufacturing can change the world of industry and lead to a new industrial revolution. In this research after reviewing mostly the different technologies and materials used in metallic AM, the application of them in a component of a passenger car engine is described. A criticality analysis is carried out in order to decide which AM development of the parts that compose the final product is more significant for the efficiency of the overall product. Based on that development a sustainability analysis is performed consisting of the analysis of the environmental impacts, the production cost analysis and the societal impact. But what has been derived from the analysis is that despite the lower environmental impact compared with the casting as a conventional method of forming of metals, AM is costly for the production of a small number of industrial products and its societal impact needs further investigation. In fact, the cost depends on the production volume, the batch size as well as the high price of the material powders and the building rates of the machines. In the future, with more advanced machines and cheaper material input the cost of metallic AM is going to drop dramatically. In spite of all the progress, the application of metallic AM is still not widespread. Since the materials as well as its technologies are still evolving, a better and more promising future is foreseen for metallic AM. Keywords: Additive Manufacturing, Direct Digital Manufacturing, Mass Production, Automotive, Internal Combustion Engine, Turbocharger, Development, Sustainability Analysis, Lifecycle AssessmentAdditive Manufacturing (AM) består av en familj av olika teknologier som bygger upp komponenter genom att lägga till material lager efter lager ett lager i taget baserat på en digital 3D solid modell. Efter trettio år av utveckling, har AM blivit en mainstream tillverkningsprocess med fler material och nya teknologier involverade i denna process. Utan tvekan har den mest dramatiska och utmanande utvecklingen inom denna grupp av teknologier varit tryckningen av metaller. Nuförtiden fortsätter användningen av AM för tillverkning av delar till slutprodukter att växa. Företag runtom i världen använder tekniken framgångsrikt för produktionen av färdiga varor. AM tillåter designoptimering och tillverkar kundanpassade delar on-demand med nästan samma materialegenskaper som konventionellt tillverkade delar. Det behövs inte användning av kylmedel, fixturer, skärverktyg och andra källor. Fördelarna med AM jämfört med konventionell tillverkning kan förändra den industriella världen och leda till en ny industriell revolution. Efter att mestadels ha gått igenom de olika tekniker och material som används i metallisk AM, beskrivs i denna forskning applikationen av dem i en komponent av motorn till en personbil. En kritikalitet analys görs för att bestämma vilken AM utveckling av de delar som utgör den slutgiltiga produkten som är viktigast för effektiviteten av den totala produktionen. Baserat på denna utveckling utförs en hållbarhetsanalys som består av en analys av miljöpåverkan, produktionskostnad och de samhälleliga effekterna. Men det som har härletts från analysen är att trots den lägre miljöpåverkan i jämförelse med gjutning som en konventionell metod för formning av metaller, är AM kostsamt för produktionen av ett fåtal industriella produkter och dess samhälleliga effekter behöver studeras ytterligare. I själva verket beror kostnaden på produktionsvolymen, satsstorleken samt det höga priset på materialpulvren och byggnadstakten av maskinerna. I framtiden, med mer avancerade maskiner och billigare material kommer kostnaden för metallisk AM att sjunka dramatiskt. Trots alla utveckling, är applikationen av metallisk AM fortfarande inte utbredd. Eftersom materialen samt dess teknik fortfarande är under utveckling förutses en bättre och mer lovande framtid för metallisk AM. Nyckelord: Additive Manufacturing, Direct Digital Manufacturing, massproduktion, bilindustrin, förbränningsmotor, Turbocharger, utveckling, hållbarhetsanalys, livscykelanalys.
18
Harris, Jonathan Andrew. "Additively manufactured metallic cellular materials for blast and impact mitigation". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271771.
Abstract (sommario):
Selective laser melting (SLM) is an additive manufacturing process which enables the creation of intricate components from high performance alloys. This facilitates the design and fabrication of new cellular materials for blast and impact mitigation, where the performance is heavily influenced by geometric and material sensitivities. Design of such materials requires an understanding of the relationship between the additive manufacturing process and material properties at different length scales: from the microstructure, to geometric feature rendition, to overall dynamic performance. To date, there remain significant uncertainties about both the potential benefits and pitfalls of using additive manufacturing processes to design and optimise cellular materials for dynamic energy absorbing applications. This investigation focuses on the out-of-plane compression of stainless steel cellular materials fabricated using SLM, and makes two specific contributions. First, it demonstrates how the SLM process itself influences the characteristics of these cellular materials across a range of length scales, and in turn, how this influences the dynamic deformation. Secondly, it demonstrates how an additive manufacturing route can be used to add geometric complexity to the cell architecture, creating a versatile basis for geometry optimisation. Two design spaces are explored in this work: a conventional square honeycomb hybridised with lattice walls, and an auxetic stacked-origami geometry, manufactured and tested experimentally here for the first time. It is shown that the hybrid lattice-honeycomb geometry outperformed the benchmark metallic square honeycomb in terms of energy absorption efficiency in the intermediate impact velocity regime (approximately 100 m/s). In this regime, the collapse is dominated by dynamic buckling effects, but wave propagation effects have yet to become pronounced. By tailoring the fold angles of the stacked origami material, numerical simulations illustrated how it can be optimised for specific impact velocity regimes between 10-150 m/s. Practical design tools were then developed based on these results.
19
Caputo, Matthew P. "4-Dimensional Printing and Characterization of Net-Shaped Porous Parts Made from Magnetic Ni-Mn-Ga Shape Memory Alloy Powders". Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1525436335401265.
20
Hopkins, Christopher David. "Development and Characterization of Optimum Process Parameters for Metallic Composites made by Ultrasonic Consolidation". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275414900.
21
Stańczak, Magda. "Behaviour of additively manufactured metallic structures under blast loading". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0073.
Abstract (sommario):
La technique de fabrication additive permet d'étudier à l'échelle du laboratoire des structures métalliques à géométrie complexe. L'application de nouvelles structures peut être particulièrement bénéfique pour améliorer la capacité d'absorption d'énergie et d'atténuation des explosions. Dans cette thèse, le rôle de la topologie des structures en aluminium AlSi10Mg fabriquées de manière additive est étudiée. Plusieurs exemplaires de structures cellulaires sont présentées. On analysera la relation entre la densité relative et les réponses de déformation des structures, ainsi que les capacités d'absorption. Le comportement de l'alliage d'aluminium AlSi10Mg imprimé est étudié afin d'étudier l'influence des conditions du processus de fabrication sur les propriétés mécaniques. Pour compléter l'étude, une analyse de la microstructure déformée est également effectuée. Les résultats obtenus prouvent la complexité du comportement du matériau. Par conséquent, un modèle phénoménologique basé sur l'approche modifiée de Johnson-Cook est proposé. Le modèle développé décrit le comportement du matériau avec une bien meilleure précision que la fonction constitutive classique. Les simulations par éléments finis réalisées avec le logiciel LS-DYNA sont utilisées pour étudier en détail les mécanismes de déformation des structures. Les résultats montrent un bon accord avec les calculs analytiques et les observations expérimentales. Les réponses indiquent qu'en sélectionnant les paramètres topologiques appropriés, il est possible d'affecter significativement les performances des structures et ainsi d'améliorer leurs propriétés d'absorption d'énergieThe additive manufacturing technique allows for studies of metallic structures with complex geometry at a laboratory scale. The application of novel structures can be especially beneficial for improving the capacity of energy absorption and blast mitigation. In the presented thesis, the role of the topology of additively manufactured AlSi10Mg aluminum structures of several exemplary cellular structures (i.e., honeycomb, auxetic, lattice, and foam) is studied at static and blast compression. Furthermore, the relationship between the relative density and the deformationresponses of the structures, as well as the energy absorption capacities is analyzed. To investigate the influence of the manufacturing process conditions on the mechanical properties, the material behavior of the printed AlSi10Mg aluminum alloy is studied. For completeness, an analysis of the deformed microstructure is also conducted. The obtained results prove the complexity of the material behavior. Therefore, a phenomenological model based on the modified Johnson-Cook approach is proposed. The developed model describes the obtained characteristics of the printed alloy with much better accuracy than the classical constitutive function. The finite element simulations conducted in LS-DYNA software are used to investigate the deformation mechanisms of the structures in detail. The results are consistent with the analytical calculations and the experimental observations. The final responses indicate that by selecting the appropriate topological parameters, it is possible to affect the performance of structures significantly and thus to improve their energy absorption properties. The resulting experiments and their modeling show that the discussed material and the manufacturing technology have a promising potential
22
Chen, Shuai. "Investigation of FEM numerical simulation for the process of metal additive manufacturing in macro scale". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI048/document.
Abstract (sommario):
La fabrication additive (FA) est devenue une nouvelle alternative pour la fabrication des pièces dans l'industrie. Cependant, il existe encore des limites pour ce procédé, en particulier la forme finale défavorable et les propriétés macroscopiques indésirables des pièces métalliques construites dans les systèmes de FA. La distorsion ou la fissure due à la contrainte résiduelle de ces pièces pose généralement de graves problèmes pour certains types de technologie de la FA métallique. Dans un système de FA, la qualité finale d'une pièce métallique dépend de nombreux paramètres de procédé, qui sont normalement optimisés par une série d'expériences sur des machines de FA. La simulation macroscopique dédiée au procédé de FA est une alternative potentielle pour les pièces métalliques fabriquées par la fabrication additive. Dans cette thèse, nous étudions d'abord le pré-processing de la simulation de FA par la méthode des éléments finis (FEM). Le procédé de fabrication additive est un phénomène multi-physique des champs couplés (champs thermique, mécanique et métallurgique). La simulation macroscopique est réalisée à deux niveaux différents. Au niveau de la couche, la reconstruction du modèle 3D est effectuée à partir du fichier de chemin de balayage de la machine de FA, basée sur la manipulation inverse de l'algorithme d'offsetting-clipping. Au niveau de la pièce, le modèle 3D de CAO est reconstruit dans un maillage des voxels, ce qui est pratique pour une pièce avec une géométrie complexe. Avec les températures de préchauffage différentes et les paramètres du procédé différents, la contrainte résiduelle d'une pièce est analysée. Ces simulations impliquent la technique potentielle pour réduire la contrainte résiduelle par l'optimisation des paramètres du procédé, au lieu de moyens traditionnels par augmenter la température de préchauffage. Basées sur la plateforme de simulation de FEM ci-dessus, deux simulations au niveau de ligne sont également étudiées dans cette thèse, visant à la relation entre le procédé de FA et la qualité finale de la pièce. Ces exemples démontrent la possibilité d'utiliser des simulations macroscopiques pour améliorer le contrôle de la qualité pendant le procédé de FA. Dans la première tâche, l'ensemble de données des paramètres de chauffage et la contrainte résiduelle sont générés par la simulation de FA. La corrélation entre eux est étudiée en utilisant des algorithmes de régression, tel que le réseau neuronal artificiel. Dans la deuxième tâche, un contrôleur de PID pour la boucle de rétroaction puissance-température est intégré dans la simulation de procédé de FA et l'auto-réglage de PID est numériquement étudié au lieu d'utiliser la machine de FA. Les deux tâches montrent le rôle important de la simulation de procédé macroscopique de FA, qui peut remplacer ou combiner les nombreuses expériences essai-erreur dans la fabrication additive métalliqueAdditive manufacturing (AM) has become a new option for the fabrication of metallic parts in industry. However, there are still some limitations for this application, especially the unfavourable final shape and undesired macroscopic properties of metallic parts built in AM systems. The distortion or crack due to the residual stress of these parts leads usually to severe problems for some kinds of metal AM technology. In an AM system, the final quality of a metallic part depends on many process parameters, which are normally optimized by a series of experiments on AM machines. In order to reduce the considerable time consumption and financial expense of AM experiments, the numerical simulation dedicated to AM process is a prospective alternative for metallic part fabricated by additive manufacturing. Because of the multi-scale character in AM process and the complex geometrical structures of parts, most of the academic researches in AM simulation concentrated on the microscopic melting pool. Consequently, the macroscopic simulation for the AM process of a metallic part becomes a current focus in this domain. In this thesis, we first study the pre-processing of AM simulation on Finite Element Method (FEM). The process of additive manufacturing is a multi-physics problem of coupled fields (thermal, mechanical, and metallurgical fields). The macroscopic simulation is conducted in two different levels with some special pre-processing work. For the layer level, the reconstruction of 3D model is conducted from the scan path file of AM machine, based on the inverse manipulation of offsetting-clipping algorithm. For the part level, the 3D model from CAD is reconstructed into a voxel-based mesh, which is convenient for a part with complex geometry. The residual stress of a part is analysed under different preheat temperatures and different process parameters. These simulations imply the potential technique of reducing residual stress by the optimisation of process parameters, instead of the traditional way by increasing preheat temperature. Based on the FEM simulation platform above, two simulations at line level are also studied in this thesis, aiming at the relation between the AM process and part's final quality. These examples demonstrate the feasibility of using macroscopic simulations to improve the quality control during the AM process. In the first task, dataset of heating parameters and residual stress are generated by AM simulation. The correlation between them is studied by using some regression algorithm, such as artificial neural network. In the second task, a PID controller for power-temperature feedback loop is integrated into AM process simulation and the PID auto-tuning is numerically investigated instead of using AM machine. Both of the two tasks show the important role of AM macroscopic process simulation, which may replace or combine with the numerous trial and error of experiments in metal additive manufacturing
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Sarentica, Atilla. "Conventional heat treatment of additively manufactured AlSi10Mg". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75056.
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Zhong, Yuan. "Sub-grain structure in additive manufactured stainless steel 316L". Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-144519.
Abstract (sommario):
The thesis focuses on exploring the sub-grain structure in stainless steel 316L prepared by additive manufacturing (AM). Two powder-bed based AM methods are involved: selective laser melting (SLM) and electron beam melting (EBM). It is already known that AM 316L has heterogeneous property and hierarchy structure: micro-sized melt pools, micro-sized grains, nano-sized sub-grain structure and nano-sized inclusions. Yet, the relation among these structures and their influence on mechanical properties have not been clearly revealed so far. Melt pool boundaries having lower amount of sub-grain segregated network structures (Cellular structure) are weaker compared to the base material. Compared with cell boundaries, grain boundaries have less influence on strength but are still important for ductility. Cell boundaries strengthen the material without losing ductility as revealed by mechanical tests. Cellular structure can be continuous across the melt pool boundaries, low angle sub-grain boundaries, but not grain boundaries. Based on the above understanding, AM process parameters were adjusted to achieve customized mechanical properties. Comprehensive characterization were carried out to investigate the density, composition, microstructure, phase, magnetic permeability, tensile property, Charpy impact property, and fatigue property of both SLM and EBM SS316L at room temperature and at elevated temperatures (250°C and 400°C). In general, SLM SS316L has better strength while EBM SS316L has better ductility due to the different process conditions. Improved cell connection between melt pools were achieved by rotating 45° scanning direction between each layer compared to rotating 90°. Superior mechanical properties (yield strength 552 MPa and elongation 83%) were achieved in SLM SS316L fabricated with 20 µm layer thickness and tested in the building direction. Y2O3 added oxide dispersed strengthening steel (ODSS) were also prepared by SLM to further improve its performance at elevated temperatures. Slightly improved strength and ductility (yield strength 574 MPa and elongation 90%) were obtained on 0.3%Y2O3-ODSS with evenly dispersed nanoparticles (20 nm). The strength drops slightly but ductility drops dramatically at elevated temperatures. Fractographic analysis results revealed that the coalescence of nano-voids is hindered at room temperature but not at elevated temperatures. The achieved promising properties in large AM specimens assure its potential application in nuclear fusion. For the first time, ITER first wall panel parts with complex inner pipe structure were successfully fabricated by both SLM and EBM which gives great confidence to application of AM in nuclear industry.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.
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Strand, Emil, e Alexander Wärnheim. "A study of micro- and surface structures of additive manufactured selective laser melted nickel based superalloys". Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188154.
Abstract (sommario):
This study examined the micro- and surface structures of objects manufactured by selective laser melting (SLM). The results show that the surface roughness in additively manufactured objects is strongly dependent on the geometry of the built part whereas the microstructure is largely unaffected. As additive manufacturing techniques improve, the application range increases and new parameters become the limiting factor in high performance applications. Among the most demanding applications are turbine components in the aerospace and energy industries. These components are subjected to high mechanical, thermal and chemical stresses and alloys customized to endure these environments are required, these are often called superalloys. Even though the alloys themselves meet the requirements, imperfections can arise during manufacturing that weaken the component. Pores and rough surfaces serve as initiation points to cracks and other defects and are therefore important to consider. This study used scanning electron-, optical- and focus variation microscopes to evaluate the microstructures as well as parameters of surface roughness in SLM manufactured nickel based superalloys, Inconel 939 and Hastelloy X. How the orientation of the built part affected the surface and microstructure was also examined. The results show that pores, melt pools and grains where not dependent on build geometry whereas the surface roughness was greatly affected. Both the Rz andRa values of individual measurements were almost doubled between different sides of the built samples. This means that surface roughness definitely is a factor to be considered when using SLM manufacturing.
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Gomez, Ortega Arturo. "Prototypage rapide de pièces en alliage d’aluminium : étude du dépôt de matière et d’énergie lors de la fusion à l’arc d’un fil par le procédé MIG-CMT". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS067/document.
Abstract (sommario):
Un nouveau procédé de fabrication additive de pièces métalliques, basé sur le procédé de soudage à l’arc appelé CMT (Cold Metal Transfert), est étudié dans l’objectif de réaliser des pièces en alliage d’aluminium Al-5Si. Un banc de fabrication additive basé sur le principe des imprimantes 3D open source, sur lequel a été intégré le procédé CMT, a été spécialement développé. Le procédé CMT permet de contrôler la fusion d’un fil d’aluminium et son dépôt sous la forme de gouttelettes sur la surface de construction, formant après solidification des « cordons » qui peuvent être superposés pour fabriquer des pièces. L’influence des paramètres du procédé sur les phénomènes de transfert de matière et de chaleur lors de la fusion du métal et de son dépôt sur la surface de construction, ainsi que sur les caractéristiques géométriques des cordons déposés, dans le cas de dépôts mono-cordon, puis dans le cas de murs formés par la superposition d’un grand nombre de cordons, est étudiée. Plusieurs défauts géométriques ont été observés, et les conditions de leur apparition analysées, grâce notamment à l’utilisation d’une caméra rapide. La compréhension des relations entre paramètres procédé, mécanismes de transfert de chaleur et de matière, et géométrie des cordons, a permis de corriger ces défauts en identifiant puis modifiant les paramètres procédé responsables de leur apparition. Enfin, une méthode de contrôle en ligne du procédé, basée sur l’analyse des signaux de tension et d’intensité produits par le générateur de soudage au cours du phénomène de dépôt, qui permet de détecter précocement l’apparition de défauts, et ainsi de modifier les paramètres procédé avant qu’ils ne s’amplifient, a été proposéeA new additive manufacturing process for metallic parts, based on the arc welding process known as CMT (Cold Metal Transfer), is studied with the objective of building parts with the aluminium alloy Al5Si. A workbench for additive manufacturing based on the 3D printers open-source principle, on which the CMT generator was integrated, was specially developed. The CMT process allows to control the aluminium wire melting and its deposition under the form of droplets on the building surface, forming, after solidification, beads that can be superposed for the parts construction. The process parameters influence on the material transfer and heat transfer during the metal melting and deposition on the build surface, as well as on the geometric characteristics of the deposed beads, in the case of mono-layer deposits, and in the case of multi-layer walls, is studied. Many geometric defects were observed, and their apparition conditions analysed, thanks in particular to the use of a high-speed camera. The understanding of the relations between the process parameters, the melting and heat transfer mechanisms, and the beads geometry, allowed the defects correction by identifying and modifying the process parameters responsible of their apparition. Finally, an on-line control method for the process, based on the analysis of the voltage and current signals produced by the welding generator during the deposition phenomena, making possible the early detection of defects, and then the modification of the process parameters before they are amplified, has been proposed
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Ratsimba, Alice. "Élaboration d’objets en cuivre par fabrication additive par extrusion de matière : Etude de la faisabilité : cas de pâtes chargées utilisant des hydrogels de polysaccarides comme systèmes liants". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0054.
Abstract (sommario):
Parmi les sept méthodes de fabrication additive appliquées aux métaux, l'extrusion de matière (Extrusion Additive Manufacturing, EAM) apparait comme une technique prometteuse pour la production de d’objets en cuivre. Ce procédé de mise en forme indirect consiste à convoyer un matériau et à le pousser à travers un orifice afin de former des cordons de matière. Ce processus de mise en forme indirecte implique le convoyage d'un matériau à travers un orifice pour former des cordons de matière. Les objets tridimensionnels sont construits par empilement de couches successives à partir d'un mélange de particules de poudre métallique et d'un système liant.Les formulations typiques de ce procédé incluent un liant thermoplastique, et les matériaux sont généralement conditionnés sous forme de filament, dont la manipulation et le convoyage sont complexes. De plus, les étapes de post-traitement sont généralement longues et nécessitent des équipements spécifiques, ce qui peut entraîner des coûts et des délais de production élevés.Dans cette perspective, l’utilisation de formulations utilisant des systèmes liants d'origine biologique semble être une alternative prometteuse, offrant des avantages potentiels en termes de rapidité de production, d’efficacité énergétique et d’impact environnemental. Les matériaux considérés sont des pâtes métalliques à base d’hydrogels de polysaccarides chargés en poudre de cuivre. L'objectif principal de ce travail est l'étude de l'adéquation du comportement de ces formulations avec le procédé de mise en forme par extrusion de matière. La définition de critères d'imprimabilité permet de comprendre les relations entre les propriétés des formulations, le déroulement du processus d'extrusion, et la qualité des objets obtenusAmong the seven additive manufacturing methods applied to metals, Extrusion Additive Manufacturing (EAM) appears as a promising technique to produce copper objects. This indirect forming process involves conveying a material and pushing it through an orifice to form strands of material. Three-dimensional objects are built by stacking successive layers from a mixture of metal powder particles and a binding system.Typical formulations for this process include a thermoplastic binder, and the materials are usually packaged in filament form, which is complex to handle and convey. In addition, post-processing steps are usually lengthy and require specific equipment, which can lead to high costs and production lead times.In this perspective, the use of formulations using biobased binder systems appears to be a promising alternative, offering potential advantages in terms of production speed, energy efficiency and environmental impact. The considered materials are metal pastes based on polysaccharide hydrogels loaded with copper powder. The main objective of this work is to study the suitability of the behaviour of these formulations with the extrusion additive manufacturing process. Defining printability criteria helps to understand relationships between the properties of the formulations, the course of the shaping process, and the quality of the obtained objects
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Engblom, Eyvind. "Effect of oxygen concentration in build chamber during laser metal deposition of Ti-64 wire". Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230638.
Abstract (sommario):
Additive manufacturing of titanium and other metals is a rapidly growing field that could potentially improve component manufacturing through optimization of geometries, less material waste and fewer process steps. Although powder-based additive manufacturing processes have so far been predominant, methods using a wire as feedstock has gained popularity due to faster deposition rates and lower porosity in deposited material. The titanium alloy Ti-6Al-4V accounts for the majority of aerospace titanium alloy consumption and as titanium is a precious and expensive resource, reducing material waste is an important factor. Laser metal deposition with wire (LMD-w) is currently used in production at GKN Aerospace in Trolhättan. One important process parameter is the oxygen level in the chamber during deposition as titanium is highly reactive with oxygen at process temperatures. Oxygen enrichment of titanium can cause embrittlement and reduced fatigue life due to formation of alpha-case, an oxygen enriched region directly beneath the surface. The oxygen level in the chamber is controlled through extensive use of protective inert gas which is a costly and time-consuming practice. The objective of this thesis was to study how elevated oxygen levels in the chamber would affect surface oxidation, chemical composition, tensile properties and microstructure. Two different sample geometries were built with Ti-6Al-4V wire at an oxygen level of 100, 500 and 850 ppm. The subsequent analysis was based around microstructural features, alpha-case formation, chemical composition in surface layers, and tensile tests. Results showed that elevated oxygen levels in the build chamber did not degrade the chemical composition or tensile properties with regard to aerospace specifications. However, significant layers of alpha-case were found in all samples indicating that subsequent processing such as machining or etching is needed.
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Sandell, Viktor. "Defects in E-PBF Ti-6Al-4V and their Effect on Fatigue Behaviour : Characteristics, Distribution and Impact on Life". Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81155.
Abstract (sommario):
Layer by layer manufacturing (additive manufacturing, AM) of metals is emerging as an alternative to conventional subtractive manufacturing with the goal of enabling near net-shape production of complex part geometries with reduced material waste and shorter lead times. Recently this field has experienced rapid growth through industrial adaptation but has simultaneously encountered challenges. One such challenge is the ability of AM metal to withstand loading conditions ranging from static loads to complex multiaxial thermo-mechanical fatigue loads. This makes fatigue performance of AM materials a key consideration for the implementation of AM in production. This is especially true for AM in the aerospace industry where safety standards are strict. Defects in metal AM materials include rough surfaces, pores and lack-of-fusion (LOF) between build layers. These defects are detrimental to fatigue as they act as local stress concentrators that can give rise to cracks in the material. Some defects can be avoided by careful build process optimization and/or post-processing but fully eliminating all defects is not possible. Because of this, a need arises for the capability to estimate the fatigue performance of AM produced critical components containing defects. The aim of the thesis is to increase understanding regarding the connection between defect characteristics and the fatigue behaviour in AM produced Ti-6Al-4V. Defect distributions are statistically analysed for use in a simple fracture mechanical model for fatigue life prediction. Other study areas include the impact of post-production treatments such as chemical surface treatments and hot isostatic pressing (HIP) on defects and fatigue behaviour. The thesis constitutes three scientific papers. The AM technique studied in these papers is Electron Beam Melting (EBM) in which an electron beam selectively melts pre-alloyed metal powder. In paper 1, defects were studied using X-ray computed tomography (XCT) and fatigue crack initiation was related to the observed defect distribution. In paper 2, XCT data was used to relate the surface morphology and roughness of post-production treated EBM material to the surface near defect distribution. The connection between this distribution and manufacturing parameter has also been explored. Paper 3 builds on and extends the work presented in paper 1 by including further fatigue testing as well as a method for predicting fatigue life using statistical analysis of the observed defect distribution. The impact of a defect on the fatigue behaviour of the material was found to largely depend on its characteristics and position relative to the surface. Production and post-processing of the material was found to play a role in the severity of this impact. Finally, it was found that a probabilistic statistical analysis can be used to accurately predict the life of the studied material at the tested conditions.SUDDEN
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Masmoudi, Amal. "Modélisation et développement expérimental du procédé de fabrication additive par fusion laser sélective d'un lit de poudre métallique : influence de la pression de l'atmosphère". Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0287/document.
Abstract (sommario):
Le procédé de fusion sélective par laser (SLM) d’un lit de poudre métallique, est un procédé de fabrication additive qui permet de fabriquer des pièces de forme complexe directement à partir d’un fichier CAO en passant par la fusion totale de couches de poudre déposées successivement. Au cours du procédé SLM l’apport d’énergie du laser à la cible engendre de nombreux cycles thermiques: fusion – vaporisation – solidification. Dans ce contexte, cette thèse a pour double objectif :1) une meilleure caractérisation et compréhension des phénomènes qui se produisent lors de l’interaction du faisceau laser avec la poudre et le bain de métal fondu à l’aide d’essais et 2) le développement d’un modèle numérique prenant en compte les phénomènes de fusion et de vaporisation de la matière ainsi que à la présence du gaz environnant à l’intérieur de la chambre de fabrication.Dans un premier temps, en considérant des géométries simples (cordons et surfaces) en acier inoxydable 316L, on a étudié l’interaction faisceau laser - lit de poudre / bain liquide métallique par différentes méthodes de diagnostics (spectrométrie, calorimètre, …) pour comprendre la nature et le rôle de la vapeur métallique générée au cours du procédé. Les résultats ont montré que cette vapeur est sans effet sur la transmission de l’énergie du laser à la matière au cours du procédé SLM. Par contre, elle conduit à la formation de condensats et peut aussi entrainer des gouttelettes de métal fondu.Ces analyses ont permis, dans un second temps, de développer un modèle numérique qui a pour objectif principal de caractériser l’influence de la pression du milieu environnant sur le processus de fusion du lit de poudre par le faisceau laser. Des paramètres caractérisant l’évolution des propriétés physiques du matériau et du milieu gazeux en fonction de la température et de la pression ont été intégrés dans les bases de données du modèle. Ces paramètres physiques du matériau ont été déterminés à partir de la littérature et d’autres ont été obtenus empiriquement à l’aide de mesures expérimentales spécifiques.Ce modèle numérique a été utilisé pour traiter le sujet principal de la thèse, à savoir celui de l’effet de la pression. Le modèle a permis de préciser les phénomènes physiques inhérents à la variation de la pression. Des manipulations expérimentales ont permis de vérifier la pertinence des données du modèle numérique proposéThe selective laser melting process (SLM) of a metallic powder bed is an innovative process that allows the manufacturing of complex shape parts directly from a CAD file via a complete melting of powder layers deposited successively. During the SLM process, the high laser energy density creates many thermal cycles: melting - vaporization - solidification.The purpose of this work was: 1) to better characterize and understand experimentally the phenomena that occur during the laser beam - powder / molten metal pool interaction and 2) to develop a numerical model taking into account the phenomena of melting and vaporizing of the material and the presence of the surrounding gas in the build chamber.In a first time, considering simple geometries (tracks and surfaces) and 316L stainless steel as material, we studied the interaction between the laser beam, the powder bed and the liquid metal pool using several experimental techniques (spectrometry, calorimetry, ...) in order to understand the nature and the role of the metal vapor generated during the process. The results showed that the vapor has no effect on the transmission of the laser beam energy to the material during the SLM process. Meanwhile it leads to the deposition of condensed vapor and also drag some molten metal droplets.In a second time a numerical model was developed to determine the influence of the pressure of the surrounding environment on the melting process of a powder bed by a laser beam. Parameters characterizing the evolution of the physical properties of the material and of the gaseous medium according to the temperature and pressure were incorporated into the model database. Some material parameters were determined from the literature and others were obtained empirically using specific experimental measurements.Finally, this numerical model, complementing experimental results, was used to treat the main subject of the thesis which is the effect of the surrounding pressure on the SLM process. The model helped to clarify the physical phenomena provided by the change in the pressure level and its validity was checked through experimental measurements
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Eriksson, Philip. "Evaluation of mechanical and microstructural properties for laser powder-bed fusion 316L". Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355882.
Abstract (sommario):
This thesis work was done to get a fundamental knowledge of the mechanical and microstructural properties of 316L stainless steel fabricated with the additive manufacturing technique, laser powder-bed fusion (L-PBF). The aims of the thesis were to study the mechanical and microstructural properties in two different building orientations for samples built in two different machines, and to summarize mechanical data from previous research on additive manufactured 316L. Additive manufacturing (AM) or 3D-printing, is a manufacturing technique that in recent years has been adopted by the industry due to the complexity of parts that can be built and the wide range of materials that can be used. This have made it important to understand the behaviour and properties of the material, since the material differs from conventionally produced material. This also adds to 316L, which is an austenitic stainless steel used in corrosive environments. To study the effect of the building orientation, samples of 316L were built in different orientations on the build plate. The density and amount of pores were also measured. Tensile testing and Charpy-V testing were made at room temperature. Vickers hardness was also measured. Microstructure and fracture surfaces were examined using light optical microscope (LOM) and scanning electron microscope (SEM). The microstructure of the 316L made with L-PBF was found to have meltpools with coarser grains inside them, sometime spanning over several meltpools. Inside these coarser grains was a finer cellular/columnar sub-grain structure. The tensile properties were found to be anisotropic with higher strength values in the orientation perpendicular to the building direction. Also high dense samples had higher tensile properties than low dense samples. The impact toughness was found to be influenced negatively by high porosity. Hardness was similar in different orientations, but lower for less dense samples. Defects due to lack of fusing of particles were found on both the microstructure sample surfaces and fracture surfaces. The values from this study compare well with previous reported research findings.
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Villaret, Flore. "Développement d’une jonction austéno-martensitique à gradient de composition chimique par fabrication additive". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI104.
Abstract (sommario):
Ces travaux de thèse concernent la problématique des liaisons bimétalliques acier austénitique/acier martensitique. Cette action de recherche se focalise sur une liaison acier austénitique 316L (X2 CrNiMo 18-12-02) / acier martensitique Fe-9Cr-1Mo (X10 CrMo 9-1). L’objectif est de comprendre la problématique métallurgique liée à l’assemblage de ces deux types de nuance et d’évaluer les possibilités de réaliser par métallurgie des poudres et par fabrication additive des transitions aciers austénitiques/aciers martensitiques. Une soudure obtenue par faisceau d’électrons sert de liaison de référence pour cette étude qui se focalise sur l’intérêt de la métallurgie des poudres pour réaliser une transition entre deux aciers. Des matériaux à gradient de composition chimique ont été consolidés par CIC et par SPS et montrent de très bonnes propriétés mécaniques et une excellente jonction entre les deux types de nuances. Par fabrication additive (DED-LB ou PBF-LB), nous obtenons aussi de très bonnes liaisons entre les deux aciers mais les microstructures sont beaucoup plus complexes. On observe curieusement que plus la vitesse de refroidissement du procédé est importante et plus la présence de ferrite dans l’acier martensitique est importante. Différents calculs basés sur la germination et la croissance de la phase austénitique ont permis de proposer un scénario cohérent pour expliquer les fractions de phases présentes dans les matériaux. La zone de transition entre les deux aciers présente, elle, de fortes variations de duretés. Ces variations sont expliquées par les changements de composition chimique, entrainant des modifications dans les températures de changement de phases, et les cycles thermiques particuliers vus lors de la fabrication. D’un point de vue technologique, les matériaux obtenus par fabrication additive présentent en traction des performances très semblables à ce que l’on obtient par soudage par faisceau d’électrons. Il est montré que la fabrication additive permet aussi de piloter le gradient de composition entre un acier martensitique et un acier austénitiqueThis PhD work concerns the problem of bimetallic austenitic/martensitic steel connections. This research action focuses on a 316L austenitic steel (X2 CrNiMo 18-12-02) / Fe-9Cr-1Mo (X10 CrMo 9-1) martensitic steel connection. The objective is to understand the metallurgical problems related to the assembly of these two steels and to evaluate the possibilities of using powder metallurgy and additive manufacturing to produce austenitic/martensitic steel transitions. A weld obtained by electron beam is used as a reference for this study which focuses on the interest of powder metallurgy to achieve a transition between two steels. Materials with a chemical composition gradient have been consolidated by HIP and SPS and show very good mechanical properties and an excellent junction between the two steels. By additive manufacturing (DED-LB or PBF-LB), we also obtain very good bonds between the two steels, but the microstructures are much more complex. Curiously, we observe that the higher the cooling rate, the higher the ferrite fraction in the martensitic steel. Different calculations based on the nucleation and growth of the austenitic phase have made it possible to propose a coherent scenario to explain the phase fractions present in the materials. The transition zone between the two steels shows strong variations in hardness. These variations are explained by changes in chemical composition, leading to modifications in phase change temperatures, and the particular thermal cycles seen during building. From a technological point of view, materials obtained by additive manufacturing have tensile performances very similar to those obtained by electron beam welding. It is shown that additive manufacturing also makes it possible to control the composition gradient between a martensitic and an austenitic steel
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Jain, Akshay Ashok. "Design and LENS® Fabrication of Bi-metallic Cu-H13 Tooling for Die Casting". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385987045.
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Hahne, William. "Optimization of laser powder bed fusion process parameters for 316L stainless steel". Thesis, Uppsala universitet, Oorganisk kemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448263.
Abstract (sommario):
The interest for additive manufacturing techniques have in recent years increased considerably because of their association to good printing resolution, unique design possibilities and microstructure. In this master project, 316L stainless steel was printed using metal laser powder bed fusion in an attempt to find process parameters which yield good productivity while maintaining as good material properties as possible. Laser powder bed fusion works by melting a powder bed locally with a laser. When one slice of the material is done, the powder bed is lowered, new powder is added on top, and the process is repeated, building the components layer by layer. In this thesis, samples produced with a powder layer thickness of 80 μm and 100 μm has been investigated. Process parameters like laser power, scanning speed and hatch spacing were investigated in order to establish clear processing windows where the highest productivity and lowest porosity are obtained. The most common defects in all sample batches were lack of fusion, gas pores, and spatter related pores. The best samples with regard to both porosity and build rate were obtained at normalized build rates between 1,3-1,6 and porosity-values in the 0,01-0,1 % range.
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Wahman, Clarence. "Corrosion of additively manufactured magnesium alloy WE43 : An investigation in microstructure and corrosion properties of as built samples manufactured with Powder Bed Fusion-Laser Beam". Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448525.
Abstract (sommario):
The work presented in this thesis was conducted at Uppsala University and at Swerim AB. The study aims to broaden the knowledge about the corrosion of additively manufactured bioresorbable alloy WE43 in humanlike conditions for future applications. Biodegradable metal implants are implants meant to stay in the body and support the wounded bone for a certain time period, and then degrade as new, healthy bone forms in its place. Magnesium alloys have properties that are desired for these kind of implants as it is biodegradable, non-toxic and matches the mechanical properties of bone. Furthermore, magnesium alloy WE43, containing yttrium, neodymium and zirconium, already exist on the market as a powder extruded screw that treats Hallux valgus, thus proves the alloys compatibility as a bioresorbable implant. However, in order to optimize implants for specific situations, additive manufacturing can be a powerful tool. By utilizing the advantages of additive manufacturing, patient specific, complex designs implant can be manufactured rapidly in order to be used in a patient. On the other hand, additive manufacturing is a complex method with many aspects affecting the outcome. Therefore it is important to study the influence that different parameters have on the material's properties, especially the corrosion properties. This thesis aims to study different power settings on the laser in the manufacturing process and what effect it has on the microstructure as well as the corrosion properties of as built WE43 samples. Samples of three different parameters settings were manufactured with a Powder Bed Fusion-Laser Beam 3Dprinter. These samples were analyzed regarding surface roughness and microstructure with Light Optical Microscope, Scanning Electron Microscope, Energy Dispersive Spectroscopy, Electron Backscatter Diffraction and Alicona InfiniteFocus. Furthermore, the corrosion properties of the samples were investigated by collecting and measuring hydrogen gas that is released during the corrosion process. In addition, the electrolyte were examined regarding the change in ion concentration and electrochemical tests were performed. It was found that the samples did not differ substantially in microstructure as all three parameter settings exhibited a matrix of magnesium and precipitates of alloying elements. However, the sample manufactured at the lowest energy density had pores incorporated in the bulk. Despite the porous bulk this sample performed best in the immersion tests and exhibited the lowest corrosion rate over 28 days. The reason for this behavior is not determined, however possible causes are discussed and further studies are recommended.
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Papavassiliou, Alessandro. "Analisi bibliografica e di mercato delle polveri metalliche utilizzabili in processi additivi". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Abstract (sommario):
In questo elaborato, dopo aver brevemente esposto i concetti preliminari della produzione additiva, verranno censite le polveri metalliche utilizzate nel settore.
In seguito, le proprietà delle polveri metalliche più utilizzate verranno confrontate in base ai dati forniti dai principali produttori ed infine verranno approfonditi aspetti legati a proprietà chimiche, meccaniche e applicative delle stesse sulla base degli studi effettuati ad oggi sulla produzione additiva, mettendone in risalto aspetti positivi e criticità.
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Pepić, Sanjin, e Otto Ridemar. "Experimental and Theoretical Investigation of Selective Laser Melted Uddeholm Dievar ®". Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254247.
Abstract (sommario):
The main problem encountered in this thesis is the lack of research and knowledge of selective laser melted-printing with Uddeholm Dievar®. This absence of information could cause issues regarding quality and properties of the alloy as well as uncertainty regarding an appropriate heat treatment cycle. This thesis mainly focuses on observing the changes that occur in the microstructure when Uddeholm Dievar® is manufactured through the additive manufacturing (AM) method known as selective laser melting (SLM). The SLM- method consists of a high-power laser that melts together thin layers of powder, one layer at a time, until a three-dimensional product is created according to selected drawings. The methodology on which this thesis is based on is the execution of a theoretical study, scientific experiments and thermodynamic calculations. Analysis of the microstructure is performed using a scanning electron microscope with techniques such as Energy-dispersive X-ray spectroscopy (EDS) and Electron backscatter diffraction (EBSD). The purpose of the methods are to map the constituent elements of the alloy and observe the orientation of the crystallographic phases in the atomic lattice respectively. The results show that the powder, both before and after printing, mainly consists of martensite with a low amount of residual austenite. The amount of primary carbides is relatively low and has been classified as MC (V-rich) and/or M6C (Mo- rich) type. The remaining residual austenite could be explained by the segregation of constituent alloying elements, where the carbon content is a dominant factor to why the MS -temperature lowers significantly causing the presence of retained austenite even though SLM has a cooling rate that varies between 103 and 108 [K/s].Det huvudsakliga problemet som denna avhandling behandlar är bristen på forskning och kunskap inom selective laser melting (SLM) 3D-printing med Uddeholm Dievar®. Avsaknaden kan leda till sämre kvalité och produktegenskaper hos legeringen. Det kan även leda till ovisshet gällande val av lämplig värmebehandling. Arbetet fokuserar på att dokumentera utformningen av stålets mikrostruktur när Uddeholm Dievar® tillverkas med den additiva tillverkningsmetoden SLM. Tillverkningsprocessen består av en högeffektslaser som detaljerat smälter samman tunna lager pulver, ett lager i taget, tills att en tredimensionell produkt skapats utefter valda ritningar. Använda metoder är; utförandet av en teoretisk studie, vetenskapliga experiment och thermodynamiska beräkningar. Analys av mikrostrukturen genomförs med hjälp av svepelektronmikroskåp där teknikerna Energy-dispersive X-ray spectroscopy (EDS) och Electron backscatter diffraction (EBSD) används. Syftet med EDS är att kartlägga de ingående elementen i legeringen, syftet med EBSD är att se orientering av de kristallografiska faserna i atomgittret. Resultaten visar på att legeringen, både före och efter printing, till största del består av martensit med en låg mängd restaustenit. Mängden primärkarbider är relativt låg och har klassifiserats som typen MC (V-rik) och/eller M6C (Mo- rik). Den kvarstående restausteniten kan möjligen förklaras av segringen av ingående legeringsämnen där kolhalten är en dominerande faktor som sänker MS-temperaturen. Detta gör att restaustenit förekommer trots den höga kylhastigheten som varierar mellan 103 och 108 [K/s] i SLM.
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Balzi, Davide. "Esecuzione di micrografie su provini in acciaio inossidabile PH1 realizzati per additive manufacturing". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Pastuschka, Lisa, e Peter Appel. "Additive Fertigung von Metallen – Einsatz des LaserCUSING®s im Bereich Automotive". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-215075.
Abstract (sommario):
Die Additive Fertigung spielt heutzutage auch in der Automobilindustrie eine bedeutende Rolle. Eine Ausprägungsform, das pulverbett-basierte LaserCUSING®-Verfahren, bietet viele neue Möglichkeiten. Im Folgenden wird zunächst ein kurzer Überblick über das Verfahren gegeben und anschließend der Einsatz des LaserCUSING®s im Bereich Automotive anhand eines gemeinsamen Projekts der EDAG Engineering GmbH, des Laser Zentrums Nord, der BLM Group und der Concept Laser GmbH verdeutlicht. Hier wurde auf Basis des EDAG Light Cocoon ein topologisch optimierter und hybrid gefertigter Spaceframe entwickelt. Die Karosserieknoten wurden mittels LaserCUSING® additiv hergestellt.
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Vandi, Daniele. "Studio del comportamento a fatica di provini in Maraging steel realizzati tramite Additive Manufacturing". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Abstract (sommario):
Nel presente lavoro di tesi verrà studiato ed analizzato, tramite prove effettuate in laboratorio, il comportamento a fatica di 3 set di provini metallici in Maraging steel, realizzati mediante le più moderne tecnologie di Additive Manufacturing.
Tale recente tecnologia, pioniera nell'ambito della produzione manifatturiera di prototipi e pezzi, ha iniziato sin dagli inizi del suo sviluppo a mostrare le sue numerose potenzialità, e solo negli ultimi anni ha dimostrato di poter essere applicata con successo anche a componenti meccanici e parti funzionali. Ciononostante, data la modernità della tecnologia, sono richieste ulteriori ricerche ed analisi per determinare il comportamento meccanico di pezzi prodotti con tali tecnologie, in quanto la loro resistenza, statica e soprattutto a fatica, è influenzata dalla peculiarità del processo tecnologico stesso, che tende a generare forte anisotropia nelle leghe metalliche prodotte.
Nella prima parte verranno discussi i fondamenti generali della meccanica per i materiali metallici, in particolare il comportamento dei materiali sottoposti a storie di carico variabile; nella seconda parte verrà presentato uno stato dell'arte dei vari processi di Additive Manufacturing; nella terza parte, verrà studiato il comportamento a fatica, ad alto numero di cicli, dei suddetti provini sottoposti da un macchinario a flessione rotante a vari livelli di carico; nella quarta parte, tramite uso di tecniche statistiche, verrà presentata un'elaborazione dei risultati ottenuti in laboratorio, in particolare per ricavare la curva S-N e il limite di fatica del materiale; infine verrà presentata l'osservazione al microscopio delle superfici di frattura dei provini, per indagare la propagazione della rottura e così risalire alle possibili cause iniziatrici della rottura stessa.
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Ståhl, Dennis, e Siyu Guo. "Innovation genom additiv tillverkning". Thesis, KTH, Maskinkonstruktion (Inst.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230585.
Abstract (sommario):
Additiv tillverkning, AM, är en teknik som utvecklas med stormsteg. Konventionella tillverkningsmetoder, som exempelvis svarvning eller formgjutning, är begränsade när det kommer till att ta fram produkter med komplexa geometrier och därför är AM ett bra komplement. Tidigare har dock andra materialegenskaper såsom brott- och sträckgräns varit något som kompenserats med inom AM. Men i den takt som AM utvecklas kan tekniken snart ersätta de flesta konventionella tillverkningsmetoderna helt. Syftet med denna rapport är att redogöra vad som är möjligt att producera med dagens AM och vad som kan förväntas i framtiden.Eftersom att komplexa former inte är ett problem med AM så går produkterna att ta fram i ett enda steg jämfört med när de tidigare blivit hopmonterade av flera mindre delar. AM i metall är något som är under snabb utveckling och i dagsläget finns det många metoder för detta, bland annat Selective Laser Sintering, Selective Laser Melting, Beam Metal Deposition, Electron Beam Melting och Binder Jetting. Metoderna använder olika typer av teknik för att skapa modeller och de har alla sina för- och nackdelar vad gäller kostnad, hållfasthet och arbetshastighet.Verktyg i alla dess former är exempel på produkter som kräver hög prestanda och lång livslängd. För att integrera de höga kraven på prestanda och möjligheterna till komplexa geometrier med AM så är det en spiralborr med invändiga kylkanaler som tas fram i denna rapport. De invändiga kylkanalerna skiftar i diameter för att optimera intaget av kylmedel samtidigt som trycket på utloppet ökar.Som tidigare nämnt finns det många metoder för AM i metall. Den metod som anses bäst lämpad för detta ändamål är Selective Laser Melting då denna metod skapar kompakta metallprodukter med hög hållfasthet. En 3D-modell av Spiralborren skapas i Solid Edge ST9 och modellen simuleras i ANSYS Workbench för att se hur kylkanalerna påverkar borren vid användning. Resultatet av simuleringen visar på att den totala deformationen blir 0,68μm och den maximalaspänningen blir 33,95MPa, båda uppstår i mitten på spiralborren. Varken totala deformationen eller spänningen i borren når alltså en kritisk gräns, och därför dras slutsatsen att detta är en konstruktion som skulle klara de krav som finns på en borr.Utvecklingen av nya metoder för AM i metall går snabbt och inom en snar framtid kommer de nya teknikerna ha så pass hög arbetshastighet och vara så pass priseffektiva att de kommer kunna ersätta de flesta konventionella tillverkningsmetoderna helt och hållet.Additive manufacturing, AM, is a technique that is developing in an incredible pace. Conventional manufacturing methods, like lathe turning or casting for instance, are limited when it comes to creating products with complex geometries, in these cases AM is a good complement. Previously though, material characteristics like tensile strength and yield point is something that AM has been compensating with. But in the current rate of development, the AM-technique can soon replace most conventional manufacturing methods completely. The purpose of this project is to describe the possibilities in AM today and what could be expected in the future.Since complex geometries is not a problem with AM, the products can be produced in only one step compared to conventional methods where it often takes several steps to produce a product. AM with metal is something that is developing fast and there are already many different methods, for instance Selective Laser Sintering, Selective Laser Melting, Beam Metal Deposition, Electron Beam Melting and Binder Jetting. These methods use different techniques to create prototypes and they all have their pros and cons what matters cost, strength and working speed.Tools in all forms are examples of products that requires high performance and a long life-span. To integrate the requirement of high performance and the possibilities with complex geometries through AM, a twisted drill with internal cooling channels is produced in this project. The internal cooling channels are shifting in diameter to optimize the inlet of coolant and at the same time increase the outlet.As mentioned earlier there are many different methods for AM in metal. The method that is considered the best for this purpose is Selective Laser Melting since this method creates compact metal products with high strength. A 3D-model of the twisted drill was created in Solid Edge ST9 and was then analyzed in ANSYS Workbench to see the impact of the internal cooling channels during use of the drill. The results show that the total deformation is 0,68μm and maximum tension is 33,95MPa, both in the middle of the drill. Neither the total deformation or the maximum tension reaches a critical limit and therefor the drawn conclusion is that this model would reach the requirements given to a drill.The development of new methods in AM with metal is going fast and in a near future the new techniques will have increased in working speed so much and be price effective enough to replace most of the conventional manufacturing methods completely.
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Tamburrini, Simone. "Produzione e caratterizzazione di componenti in WC-Co mediante selective laser melting". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Abstract (sommario):
Uno dei temi chiave della ricerca sull’Additive Manufacturing (AM) è l’accrescimento del campo di materiali processabili. La tecnologia garantisce diversi vantaggi rispetto alle normali tecniche di lavorazione ma richiede esperienza nella lavorazione e conoscenza del materiale. Nello studio oggetto di questa dissertazione si mostrano i risultati di un primo approccio alla lavorazione di WC-Co (carburo di tungsteno in matrice di cobalto) attraverso Selective Laser Melting (SLM). Lo scopo è di gettare le basi per un processo che permetta la produzione di utensili da taglio in WC-Co. Lo studio si è incentrato su un’attenta analisi microstrutturale di diversi gruppi di campioni processati attraverso SLM e prodotti a partire da due polveri a diverso contenuto di Co (9% e 17%). Le densità, le durezze e le microstrutture ottenute sono state confrontate con quelle relative a prodotti sinterizzati industriali. Lo studio ha portato a nuove conoscenze sulla microstruttura del materiale derivante dalla lavorazione ed ha permesso di stabilire relazioni tra parametri di processo e densità del prodotto finale. Per l’ultimo gruppo di campioni prodotto (17% di Co) si è ottenuto un miglioramento in termini di qualità del materiale prodotto, nel particolare si è incrementata la densità e ridotta l’estensione di difetti microstrutturali quali cricche e porosità.
43
Borsari, Mattia. "Studio di strutture reticolari metalliche stampate con tecnologia additiva a letto di polvere e analisi del comportamento a fatica tramite DIC (Digital Image Correlation)". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Abstract (sommario):
Questo elaborato offre uno spunto sullo stato dell’arte della tecnologia SLM (Selective Laser Melting) con particolare attenzione all’influenza dei parametri di processo sulla qualità del prodotto finale; propone svariati esempi di prove meccaniche quasi statiche e di fatica eseguite sulle celle più comuni in letteratura, sottolineando la varietà dei difetti legati al meccanismo di fusione e alla scelta di parametri di stampa non ottimizzati; mette in luce l’importanza della DIC (Digital Image Correlation) per la comprensione della dinamica eterogenea del comportamento delle strutture reticolari.
A questa prima parte si aggiunge una campagna sperimentale svolta su provini in CoCrMo, nelle condizioni as build e dopo un trattamento termico, dedicata allo studio delle prestazioni a fatica in condizioni compression-compression per la costruzione della curva di Wöhler. Tutte le prove sono monitorate registrando sequenze di foto per ciascun campione in momenti diversi del test e destinate all’analisi DIC mediante il software GOMcorrelate®.
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Conti, Alfredo. "Tecniche della manifattura additiva - applicazioni in ambito aeronautico e aerospaziale". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13306/.
Abstract (sommario):
Il potenziale delle nuove tecnologie digitali applicate al settore industriale ha consentito di ridurre enormemente la durata dei cicli produttivi grazie alla rapida gestione di quantità di dati sempre più considerevoli attraverso l’introduzione delle Macchine a Controllo Numerico (Computer Numerical Control – CNC).
Nel corso delle ultime tre decadi, l’industria manifatturiera ha subito notevoli e sostanziali cambiamenti grazie ad una sempre più forte connessione con il mondo dell’informatica.
La più grande rivoluzione in tale ambito è stata segnata dall’avvento della Manifattura Additiva (Additive Manufacturing - AM), conosciuta sotto diversi nomi, tra i quali Prototipazione Rapida (Rapid Prototyping), Manifattura Rapida (Rapid Manufacturing) o Libera Fabbricazione di Forme (Free Form Fabrication).
Materia di ricerca e sviluppo sin dalla fine degli anni ’80, la Manifattura Additiva consente la creazione di elementi fisici tridimensionali partendo da modelli CAD attraverso la sovrapposizione successiva di materiale strato per strato (layer by layer), offrendo i benefici di una elevata flessibilità geometrica degli elaborati, altrimenti irraggiungibile attraverso le tradizionali tecniche di Manifattura Sottrattiva operanti per asportazione di materiale. In seguito ad intensive ricerche, progressi significativi sono stati fatti nello sviluppo e nella commercializzazione di nuovi ed innovativi processi AM.
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Zanini, Filippo. "X-ray computed tomography for coordinate metrology and industrial applications". Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3425370.
Abstract (sommario):
X-ray computed tomography (CT) has emerged as innovative measuring technique for dimensional metrology in industry over the last years. Thanks to unique capabilities, CT provides several advantages in comparison with other well-established coordinate measuring systems (CMSs). In particular, CT allows obtaining a holistic three-dimensional model of the scanned workpiece and performing non-destructive and non-contact measurements of outer as well as inner features and geometries difficult to access. However, important drawbacks limit a wider acceptance of this technology in industry. One of the most critical problems is the complexity of metrological traceability establishment due to difficulties in evaluating the task-specific uncertainty, as well as specification and determination of metrological performances of CT systems. In fact, a dedicated international standard for CT acceptance test and performance verification is still under development.
In this thesis, experimental activities were mainly oriented at evaluating and improving CT metrological performances. The material influence on length measurement errors was studied by investigations based on two reference objects: aluminium hole plate, with significant material effect and ruby ball plate, with negligible material influence. The obtained results contributed to the test survey organized on this topic by the ISO working group that is developing the future ISO standard for CT.
The image quality of the 2D projections acquired by CT is fundamental for achieving a good reconstruction quality. It is directly connected to the image blurring content and, consequently, to the focal spot quality. In this thesis, new methods developed to assess the focal spot drift and size are presented.
Considering the entire CT measurement procedure, an important metrological characteristic to be evaluated is the metrological structural resolution (MSR). Despite several methods for MSR evaluation have been proposed, a standard test to be included in the ISO standard for CT has still to be defined. In this thesis, the ‘Hourglass’ method –developed by the University of Padova– was selected to evaluate the MSR. The method was improved by measuring a high number of distances and by applying a definition of MSR similar to the one proposed by the guideline VDI/VDE 2617-13. Moreover, the method concept was compared with concepts of other proposed methods. Finally, the main influence quantities affecting the method were identified and evaluated.
Since CT is a multi-purpose measuring technique, it has become attractive for many industrial applications. However, the accuracy of CT measurement results is often unknown. For this reason, the evaluation of CT accuracy for specific measurement tasks as well as the comparison with other well-established evaluation methods is crucial for the acceptance of CT in industry. In this thesis, two industrial case studies were addressed: (i) porosity analysis for metal additive manufactured parts and (ii) wear evaluation of polymeric prosthetic components. In the first study, CT was compared with other inspection techniques such as Archimedes method, gas pycnometry and microscopic analysis of cross-sections. A multisensory CMM was used as well in order to get reliable reference area values for pores lying on selected cut sections. In the second study, the proposed CT-based method was validated through comparison with the gravimetric method, which is the current reference method used for wear assessment.La tomografia computerizzata a raggi-X (CT) si è affermata negli ultimi anni come tecnologia di misura innovativa per la metrologia dimensionale nel settore industriale. L’utilizzo di un sistema CT industriale comporta una serie di importanti vantaggi nei confronti di altri sistemi di misura a coordinate (CMSs). In particolare, il CT consente di ottenere un modello tridimensionale completo dell’oggetto scansionato e di condurre misure non distruttive e non a contatto di geometrie e caratteristiche sia esterne sia interne e di difficile accesso. Tuttavia, alcuni svantaggi rilevanti limitano una più estesa diffusione di questa tecnologia nel settore industriale. Uno dei problemi più critici risiede nella riferibilità metrologica delle misure CT, complicata dalla difficoltà nel determinare l’incertezza di misura e nel valutare le prestazioni metrologiche dei sistemi CT. Inoltre, uno standard internazionale dedicato ai test per l’accettazione e per la verifica delle prestazioni dei sistemi CT è tuttora in via di sviluppo. Le attività sperimentali presentate in questo lavoro di tesi sono state focalizzate principalmente sulla valutazione e sul miglioramento delle prestazioni metrologiche del CT. L’influenza del materiale sugli errori di misura di lunghezza è stata studiata mediante indagini basate su due campioni di riferimento: una hole plate di alluminio, caratterizzata da un’influenza significativa del materiale e una ball plate di rubino, caratterizzata da un’influenza del materiale trascurabile. I risultati ottenuti hanno contribuito alla campagna sperimentale incentrata su questo argomento organizzata dal working group dedicato allo sviluppo del futuro standard ISO per il CT. La qualità d’immagine delle proiezioni radiografiche bidimensionali acquisite mediante CT è fondamentale per ottenere una buona qualità nella ricostruzione del modello tridimensionale dell’oggetto scansionato. Essa è connessa al concetto di blurring o sfocatura dell’immagine e, di conseguenza, alla qualità della macchia focale da cui viene emesso il fascio di raggi X. All’interno di questa tesi vengono descritti nuovi metodi sviluppati per valutare l’effettiva dimensione della macchia focale e l’eventuale drift che essa può subire durante una scansione tomografica. Considerando l’intera procedura di misura CT, una caratteristica metrologica molto importante da considerare è la risoluzione strutturale metrologica (MSR). Nonostante siano stati proposti diversi metodi per la valutazione della MSR, un test univoco da includere nel futuro standard ISO dedicato al CT deve ancora essere definito. In questa tesi, il metodo ‘Hourglass’ – sviluppato dall’Università di Padova - è stato selezionato per valutare la MSR. Questo metodo è stato migliorato mediante la misura di un elevato numero di distanze e applicando una definizione di MSR simile a quella proposta dalla linea guida tedesca VDI/VDE 2617-13. Inoltre, il concetto alla base di tale metodo è stato confrontato con quello di altri metodi e i principali fattori che possono influenzarne i risultati sono stati identificati e valutati. Essendo la tomografia computerizzata a raggi-X una tecnica di misura molto versatile, il suo potenziale può essere sfruttato da un gran numero di applicazioni industriali. Tuttavia, l’accuratezza dei risultati di misura CT è spesso ignota. Per questa ragione, la determinazione dell’accuratezza di misura e il confronto con altri metodi di misura consolidati sono cruciali per una piena accettazione del CT in ambito industriale. In questa tesi sono stati affrontati due casi di rilevanza industriale: (i) analisi di porosità su componenti metallici realizzati mediante produzione additiva e (ii) determinazione dell’usura di componenti protesiche in polietilene. Per quanto riguarda il primo studio, il CT è stato confrontato con altre tecniche d’indagine: metodo di Archimede, picnometro a gas e analisi microscopica di sezioni di taglio. In aggiunta, una macchina di misura a coordinate (CMM) multi-sensore è stata utilizzata per ottenere valori di riferimento per l’area di un certo numero di pori distribuiti su alcune sezioni di taglio selezionate. Nel secondo studio, il metodo CT proposto è stato validato mediante confronto con il metodo gravimetrico, che è l’attuale metodo di riferimento utilizzato per la determinazione del grado di usura.
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Säger, Florian. "A Feasibility Study of an Automated Repair Process using Laser Metal Deposition (LMD) with a Machine Integrated Component Measuring Solutio". Thesis, KTH, Industriell produktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-248022.
Abstract (sommario):
The repair of worn or damaged components is becoming more attractive to manufacturers, since it enables them to save resources, like raw material and energy. With that costs can be reduced, and profit can be maximised. When enabling the re-use of components, the lifetime of a component can be extended, which leads to improved sustainability measures. However, repair is not applied widely, mainly because costs of repairing are overreaching the costs of purchasing a new component. One of the biggest expense factors of repairing a metal component is the labourintense part of identifying and quantifying worn or damages areas with the use of various external measurement systems. An automated measuring process would reduce application cost significantly and allow the applications to less cost intense component. To automate the repair process, in a one-machine solution, it is prerequisite that a measuring device is included in the machine enclosure. For that, different measuring solutions are being assessed towards applicability on the “Trumpf TruLaser Cell 3000 Series”. A machine that uses the Laser Metal Deposition (LMD) technology to print, respectively weld, metal on a target surface. After a theoretical analysis of different solutions, the most sufficient solution is being validated by applying to the machine. During the validation a surface models from a test-component is generated. The result is used to determine the capability of detecting worn areas by doing an automated target-actual comparison with a specialised CAM program. By verifying the capability of detecting worn areas and executing a successful repair, the fundamentals of a fully automated repair process can be proven as possible in a one-machine solution.Tillverkare har börjat se stora möjligheter i att reparera slitna eller skadade komponenter som ett sätt att spara resurser, så som råmaterial och energi. Med den besparingen minskar kostnaderna och vinsten kan således maximeras. Reparation möjliggör även återanvändning av komponenter, vilket förlänger komponentens livslängd och leder till förbättrade hållbarhetsåtgärder. Dock tillämpas reparation inte i någon stor utsträckning i nuläget, främst eftersom kostnaderna för reparation överstiger kostnaderna för att köpa en ny komponent. En av de största kostnaderna för att reparera en metallkomponent är att identifiera och kvantifiera slitna eller skadade områden med hjälp av olika externa mätsystem, som är en väldigt arbetsintensiv process. En automatiserad mätprocess skulle minska avsökningskostnaden avsevärt och således reducera den totala kostnaden för komponenten. För att möjliggöra en automatiserad reparationsprocess i en enda maskinlösning är det en förutsättning att en mätanordning ingår i maskinhöljet. Därför har olika mätningslösningar utvärderats med avseende på användbarhet i "TRUMPF TruLaser Cell 3000 Series", vilket är en maskin som använder Laser Metall Deposition-teknik (LMD-teknik) för att skriva ut och svetsa metall på en definierad yta. En teoretisk analys av olika lösningar har utförts, där den teoretiskt mest lämpliga lösningen validerades genom att appliceras till maskinen. Valideringen genererade en modell av ytan av en testkomponent. Sedan utfördes en automatiserad, målrelaterad jämförelse med ett specialiserat CAM-program baserat på modellresultatet, för att bestämma möjligheten att upptäcka slitna områden. Genom att verifiera förmågan att upptäcka slitna områden samt genomförandet av en lyckad reparation kan grunden för en helt automatiserad reparationsprocess bevisas som möjlig i en enda maskinlösning.
Das reparieren von abgenutzten oder beschädigten Komponenten wird immer attraktiver für Hersteller. Es ermöglicht es Ressourcen einzusparen wie beispielsweise Rohmaterial und Energie, was die Lebenszeit einer Komponente verlängert und damit die Nachhaltigkeit verbessert. Allerdings ist Reparieren nach wie vor nicht weit verbreitet, hauptsächlich dadurch bedingt, dass die Reparaturkosten die Kosten für eine neue Komponente übersteigen. Einer der größten Kostenfaktoren des reparieren einer Metallkomponente ist der Arbeitsintensive Teil der Identifizierung und Quantifizierung des abgenutzten oder beschädigten Bereichs mit verschiedensten externen Vermessung Systemen. Ein automatisierter Vermessungsprozess würde die Kosten signifikant reduzieren und neue Applikationen ermöglichen. Das automatisieren der gesamte Prozesskette – in einer Single-Maschinenlösung – erfordert, dass eine Messeinrichtung im Bearbeitungsraum der Maschine angebracht wird. Dafür werden verschiedene Lösungen nach Anwendbarkeit an der Trumpf Laser Cell 3000 Serie hin beurteilt. Eine Maschine, welche Laser Metal Deposition (LMD) als Technologie anwendet um Material auf Oberflächen aufzubringen. Nach einer theoretischen Analyse verschiedener Lösungen wird die beste Lösung va durch anbringen an die Maschine validiert. Bei der Validierung wird ein Oberflächenmodel erzeugt. Das Ergebnis wird dann genutzt um die Fähigkeit zu belegen, dass beschädigte Stellen, durch einen Soll-Ist-Vergleich in einem speziellen CAM Programm, automatisch detektiert werden können. Basierend auf diesem Beleg und mit dem Ergebnis eine Komponente erfolgreich reparieren zu können, gilt die These eines automatisierten Reparaturprozesses in einer Single-Maschinenlösung als beweisen.
47
Costa, José Manuel Monteiro. "METAL-BASED ADDITIVE MANUFACTURING: Evaluation of metallic parts produced with Additive Manufacturing Technology at YAZAKI Europe Limited". Master's thesis, 2016. https://hdl.handle.net/10216/87466.
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Costa, José Manuel Monteiro. "METAL-BASED ADDITIVE MANUFACTURING: Evaluation of metallic parts produced with Additive Manufacturing Technology at YAZAKI Europe Limited". Dissertação, 2016. https://hdl.handle.net/10216/87466.
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Lin, Yan-Ji, e 林延輯. "Fe-based metallic glass powder preparation and additive manufacturing workpiece properties analysis". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/26856326799082501680.
Abstract (sommario):
碩士國立中央大學
材料科學與工程研究所
105
The alloy composition of Fe-Cr-Mo-C-B-Y-Co 7 components Fe-based alloy was selected as the master alloy and prepared by vacuum induction melting. Then the alloy ingots were re-melted and fabricated into spherical alloy powder by inert gas atomization process in the Material and Chemical Laboratories, Industrial Technology Research Institute (ITRI, Hsinchu). After size sieving, XRD analysis, and SEM examination, the atomized powders which can meet the specification of additive manufacturing were collected to do the linear laser melting test and cube selective laser melting (SLM) test. Hopefully, the optimum process parameters of SLM that is suitable for additive manufacturing can be designed. After size sieving, the particle size of the most amount powder locates around 37~44 μm. According to the XRD results, all the powders which particle size below 63 μm are confirmed to be amorphous. On contrary, the structure of the powders with particle size more than 63 μm was found to contain an amorphous matrix co-existing with a C23C6, crystalline phase. The intensity of the C23C6 peak increases with increasing the powder size. Meanwhile, a spherical or near-spherical appearance can be clearly observed by SEM examination for all powders. 10 sets parameters of laser power and scanning rate were obtained from the results of linear laser melting test by OM observation. Then these 10 sets parameters and an additional parameter (which can successfully apply on produce maraging steel sample) were applied to do the cube SLM test. After SLM, cracks and spalls were found on the side view of most SLM cubes except the cubes made by the parameters of P240-S650 (#7), P240-S700(#8), and the parameter for maraging steel (#11). However, after the SEM examination on the cube samples made by parameters of #7, #8, and #11, respectively, there still can be found several unmelted powder particles on the surface of cube sample which made by the parameters of #8 and #11. In parallel, the laser melted powder layers of the cube sample made by # 11 parameter exhibit an insufficient fusion condition and the separated powder particles still can be seen on the side view of cube sample. Although there are no unmelted powder on the cube surface and no insufficient fusion condition on the side view for the cube sample made by #7 parameter, but there is one crack throughout the whole cube sample. On the other hand, there are only few unmelted powder particles on the sample surface, no clear separation of laser melted powder layers, and no obvious creaking can be found in the cube sample made by #8 parameter. Moreover, the cube sample made by parameter #8 presents higher hardness than the samples made by the parameters of #7 and #11, which means that the cube sample made by #8 parameter possesses higher product density than the other. In summary, #8 parameter seems the optimum process condition in this study and can be applied as the reference for the further laser additive manufacturing the Fe-based amorphous alloy. Keyword: Fe-based metallic glass, atomization process, additive manufacture
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Oliveira, Bernardo Garrett Neuparth Moura de. "Fatigue behaviour of metallic components obtained by topology optimization for additive manufacturing". Master's thesis, 2019. https://hdl.handle.net/10216/122446.