<p>This study is focused on the prediction of residual stresses and microstructure development of steel and aluminum alloys during laser-based manufacturing processes by means of multi-physics numerical modeling.</p> <p>A finite element model is developed to predict solid-state phase transformation, material hardness, and residual stresses produced during laser-based manufacturing processes such as laser hardening and laser additive manufacturing processes based on the predicted temperature and geometry from a free-surface tracking laser deposition model. The solid-state phase transformational model considers heating, cooling, and multiple laser track heating and cooling as well as multiple layer tempering effects. The residual stress model is applied to the laser hardening of 4140 steel and to laser direct deposition of H13 tool steel and includes the effects of thermal strain and solid-state phase transformational strain based on the resultant phase distributions. Predicted results, including material hardness and residual stresses, are validated with measured values.</p> <p>Two dendrite growth predictive models are also developed to simulate microsegregation and dendrite growth during laser-based manufacturing processes that involve melting and solidification of multicomponent alloys such as laser welding and laser-based additive manufacturing processes. The first model uses the Phase Field method to predict dendrite growth and microsegregation in 2D and 3D. It is validated against simple 2D and 3D cases of single dendrite growth as well as 2D and 3D cases of multiple dendrite growth. It is then applied to laser welding of aluminum alloy Al 6061 and used to predict microstructure within a small domain. </p> The second model uses a novel technique by combining the Cellular Automata method and the Phase Field method to accurately predict solidification on a larger scale with the intent of modeling dendrite growth. The greater computational efficiency of the this model allows for the simulation of entire weld pools in 2D. The model is validated against an analytical model and results in the literature.

<div> <p>Metal-organic frameworks (MOFs) are a class of compounds consisting of metal ions or clusters coordinated to organic ligands in porous structure forms. MOFs have been proposed in use for gas adsorption, purification, and separation applications. This work combines MOFs with 3D printing technologies, in which 3D printed plastics serve as a mechanical structural support for MOFs powder, in order to realize a component design for gas adsorption. The objective of the thesis is to understand the gas adsorption behavior of MIL-101 (Cr) MOF coated on 3D printed PETG, a glycol modified version of polyethylene terephthalate, through a combined experimental and modeling study. The specific goals are: (1) synthesis of MIL-101 (Cr) MOFs; (2) nitrogen gas adsorption measurements and microstructure and phase characterization of the MOFs; (3) design and 3D printing of porous PETG substrate structures; (4) deposition of MOFs coating on the PETG substrates; and (5) Monte Carlo (MC) modeling of sorption isotherms of nitrogen and carbon dioxide in the MOFs.</p><p>The results show that pure MIL-101 (Cr) MOFs were successfully synthesized, as confirmed by the scanning electron microscopy (SEM) images and X-ray diffrac- tion (XRD), which are consistent with literature data. The Brunauer-Emmett-Teller (BET) surface area measurement shows that the MOFs samples have a high cover- age of nitrogen. The specific surface area of a typical MIL-101 (Cr) MOFs sample is 2716.83 m2/g. MIL-101 (Cr) also shows good uptake at low pressures in experimental tests for nitrogen adsorption. For the PETG substrate, disk-shape plastic samples with a controlled pore morphology were designed and fabricated using the fused de-</p><p> </p><p>position modeling (FDM) process. MOFs were coated on the PETG substrates using a layer-by-layer (LbL) assembly approach, up to 30 layers. The MOFs coating layer thicknesses increase with the number of deposition layers. The computational model illustrates that the MOFs show increased outputs in adsorption of nitrogen as pres- sure increases, similar to the trend observed in the adsorption experiment. The model also shows promising results for carbon dioxide uptake at low pressures, and hence the developed MOFs based components would serve as a viable candidate in gas adsorption applications.</p><div><br></div></div>

- Creo 5.0 enhancements - New extensions: Creo Flow Analysis, Topology Optimization - Futures

Dans le domaine de la fabrication additive plusieurs technologies cohabitent et présentent des maturités et des applications différentes : le lit de poudre, la projection de poudre et le dépôt de fil pour ne citer que les principales. Nous avons étudié, dans le cadre de cette thèse, la réalisation de pièces de grandes dimensions du domaine aéronautique en alliage d’aluminium, par technologie WAAM (Wire Arc Additive Manufacturing) robotisée. Cette technologie repose sur l’utilisation un générateur de soudure à l'arc, d’un système de protection gazeuse et d’un système d'alimentation en métal d'apport sous forme de fil. Pour répondre à cette problématique, plusieurs voies de recherche ont été investiguées. La première traitait principalement de la génération de trajectoires : Plusieurs expérimentations ont permis de montrer l’intérêt et l’importance de la génération de trajectoires et notamment la maitrise de l’orientation outil pour la fabrication additive de pièces complexes en étudiant le respect de la géométrie souhaitée. La seconde concernait l’étude de la santé matière des pièces fabriquées. Des observations au niveau de la microstructure, mais aussi des caractéristiques mécaniques ont permis de mettre en évidence l’influence des paramètres opératoires sur la qualité de la matière déposée. Enfin, la réalisation de pièces fonctionnelles dans le cadre d’un projet financé par la DGA/DGAC et dont les partenaires étaient : STELIA, CONSTELLIUM, CT INGENIERIE et l’Ecole Centrale de Nantes, a permis de mettre en avant l’intérêt du procédé pour la fabrication de pièces aéronautiques. Un élément de structure aéronautique composé de raidisseurs a été fabriqué avec le procédé WAAM sur un substrat double courbure en alliage aluminium. Les difficultés accrues de réalisation ont pu être levées par l'emploi de la méthodologie développée dans le cadre de la thèse. / In the field of additive manufacturing (AM), several processes are present and have different applications and levels of development: the main technologies are powder-bed based AM, powder projection and Wire Additive Manufacturing (WAM). We have studied, in this PhD work, the manufacturing of large scale components in aluminum alloy for aircraft industry with Wire Arc Additive Manufacturing (WAAM). This technology is based on a welding generator, a shielding gas protection and a feedstock (wire in this case). To solve this issue, several ways of research were investigated. The first one dealt with toolpath generation: several experiments have highlighted the importance of tool path generation and the tool orientation to manufacture complex parts and improve the part accuracy. The second one was about the validation of the material quality after deposit. Microstructural observations and mechanical tests have demonstrated the effect of process parameters on the deposit quality. Finally, in the context of a DGA/DGAC funded research project, whose partners were STELIA, CT INGENIERIE, CONSTELLIUM and l’Ecole Centrale de Nantes, the manufacturing of functional part in aluminum alloy has shown the interest of the process for aircraft industry. A structural component based on a double curvature geometry has been manufactured with WAAM. The methodologies developed in this PhD work have enabled us to solve the issues to manufacture that type of component.

Additive Manufacturing (AM) is a fast-developing technology, that despite itspotential is yet to be applied by the mainstream healthcare market. Comparedto other clinical areas where AM is applied, cardiology has a negligible marketshare, why this thesis aimed at identifying barriers and facilitators for AMimplementation, as well as presenting a framework with factors to considerwhen attempting to implement AM. A literature review outlined aspects currently considered in literature, inrelation to the barriers and facilitators of implementing AM in cardiology. Toidentify barriers and facilitators to AM implementation in cardiology, and tocomplement the literature review, two exploratory case studies were carriedout, which had a comparative design. The case studies took place in Sweden,whereof one has already implemented AM in cardiology, and the other one hasnot. Purposive sampling was applied to choose the two involved hospitals, whileconvenience sampling and snowball sampling were used for selecting interviewparticipants. The findings were analyzed using a thematic analysis. Results show that barriers and facilitators can act on an individual,organizational, and industrial level. Barriers and facilitators were divided intothe themes Management, Technology, Network, Behavior, and Market. Aspectsfalling under the theme Management were mentioned most frequently amongthe respondents, suggesting that such barriers and facilitators play a significantrole in implementing AM, while findings placed in the Network and Behaviortheme respectively were not previously addressed in literature. Barriersinclude, among others, low involvement of leaders, little cross disciplinarycollaboration, and lack of innovation resources in health care. Facilitatorsinclude, among others, having an innovation culture that supports initiation ofprojects, providing an easy and intuitive system for ordering a 3D model, andpromoting the technology among potential users. Concluded is that AM implementation faces numerous barriers and facilitatorswhich should be considered before an implementation endeavor. Addressingthese on an individual, organizational, and industrial level most likely facilitatesthe process of AM implementation, leading to a successful and sustainablechange in the organization.

The need for reliable and cost-effective testing procedures for Additive Manufacturing (AM) is growing. In this Dissertation, the development of a new computational-experimental method based on the realization of specific testing artifacts to address this need is presented. This research is focused on one of the widely utilized AM technologies, Fused Deposition Modeling (FDM), and can be extended to other AM technologies as well. In this method, testing artifacts are designed with simplified boundary conditions and computational domains that minimize uncertainties in the analyses. Testing artifacts are a combination of thin and thick cantilever structures, which allow measurement of natural frequencies, mode shapes, and dimensions as well as distortions and deformations. We apply Optical Non-Destructive Testing (ONDT) together with computational methods on the testing artifacts to predict their natural frequencies, thermal flow, mechanical properties, and distortions as a function of 3D printing parameters. The complementary application of experiments and simulations on 3D printed testing artifacts allows us to systematically investigate the density, porosity, moduli of elasticity, and Poisson’s ratios for both isotropic and orthotropic material properties to better understand relationships between these characteristics and the selected printing parameters. The method can also be adapted for distortions and residual stresses analyses. We optimally collect data using a design of experiments technique that is based on regression models, which yields statistically significant data with a reduced number of iterations. Analyses of variance of these data highlight the complexity and multifaceted effects of different process parameters and their influences on 3D printed part performance. We learned that the layer thickness is the most significant parameter that drives both density and elastic moduli. We also observed and defined the interactions among density, elastic moduli, and Poisson’s ratios with printing speed, extruder temperature, fan speed, bed temperature, and layer thickness quantitatively. This Dissertation also shows that by effectively combining ONDT and computational methods, it is possible to achieve greater understanding of the multiphysics that governs FDM. Such understanding can be used to estimate the physical and mechanical properties of 3D printed components, deliver part with improved quality, and minimize distortions and/or residual stresses to help realize functional components.

A composite part manufacturing mold was considered one of the most important factors that affected a successful composite part manufacturing process for this research. A highly durable surface was required for the mold to prevent surface damages and increase mold life. A high surface finish quality of the mold improved the surface quality of the composite part and lowered the demolding force. However, the surface of additively manufactured fiber reinforced composite molds usually had lower durability and surface finish quality compared to traditional metal molds. To solve these issues, the author applied an additional coating on top of the additively manufactured fiber reinforced composite mold surface. A thermal analysis of the additively manufactured fiber reinforced composite material and the coating material were performed to select an applicable coating technique and coating material. The thermoset polymer coating with ceramic particles that was applied with a liquid spray coating technique was selected as a coating material. Various surface property tests were performed to evaluate the coated surface compared to the non-coated surface. The additively manufactured fiber reinforced composite test specimen manufacturing process and the coating application process were demonstrated in this study. The surface durability of the test specimens was tested using a surface hardness test and an abrasion resistance test. The surface performance of the test specimens was measured using a surface roughness test and a demolding test. The sustainability of the coating material on the additively manufactured fiber reinforced composite was tested using coefficient of thermal expansion (CTE) test, coating adhesion test, and mold life experiment. In the mold life experiment, the non-coated and coated mold were used for multiple composite part manufacturing processes to investigate how the coating affected the life of the mold. The test results showed that the coated surface had a significantly improved surface abrasion resistance and demolding performance. However, the coating did not significantly improved surface hardness and roughness with the coating. The adhesion strength of the coating was not degraded even there was a coefficient of thermal expansion (CTE) mismatch between the additively manufactured fiber reinforced composite and the coating material. The coated additively manufactured fiber reinforced composite mold was able to be used for multiple autoclave composite part manufacturing cycles. The coating covered most of the small voids on the mold surface and provided a more homogeneous surface compared to the non-coated mold, but the voids which could not be covered with the coating caused a chipped coating issue. Once the chipped coating occurred, the size of chipped coating got larger each time the tool was used for a composite part manufacturing cycle. Although the additional coating provided some improvements for the surface properties, the coating applied in this research could not be an ultimate solution to meet all the surface property requirements for composite part manufacturing mold.

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.

Detta kandidatexamensarbete fokuserar på möjligheterna att implementera additiv tillverkning på en styrspindel, en av nyckelkomponenterna i en Formula Student-bil. Målet var att få en inblick i denna tillverkningsteknologi och se om det skulle vara lämpligt att byta KTH Formula Students nuvarande styrspindlar i aluminium (Alumec 89) till att vara gjorda av titan (Ti6AL4V) utan att öka vikten, samt inte förlora styvhet och styrka i konstruktionen. Baserat på den nuvarande geometrin av styrspindeln för KTH Formula Students senaste bil, eV12, designades nya styrspindlar i titan med programmet SolidWorks. Denna process gjordes med hjälp av erfarenhet inom styrspindelskonstruktion och intuition, genom att analysera och förändra designen i en iterativ process. Tre konstruktioner gjordes: en lätt version av den exisisterande, vilken var baserad på den existerande styrspindeln i aluminium, en ihålig version och en okonventionell version som utnyttjar designmöjligheter med additiv tillverkning. För att verifiera de tre olika titankonstruktionerna utfördes det en analys av den existerande styrspindeln. Genom att använda resultatet från denna analys kunde mål för styvhet och maximal spänning sättas för den nya titanstyrspindeln. Ingen av koncepten uppnådde de satte målen fullt ut, men värdefull insikt i design, hållfasthetslära och tillverkningsteknik erhölls. Det faktum att den specifika styvheten för titan är lägre än den för aluminium betyder att skulle vara svårt att göra en fungrande design utan användning av topologioptimeringsmjukvara, om vikt är en av de viktigaste faktorerna. Med mer bearbetningstid skulle dessa konstruktioner troligtvis kunna möta målen. / This bachelor thesis focuses on the possibility to implement additive manufacturing on the upright, one of the key components in a Formula Student car. The goal was to get an insight into this manufacturing technology and to see if it would be suitable to change KTH Formula Student’s current aluminium (Alumec 89) uprights to titanium (Ti6AL4V) ones, without gaining weight and losing stiffness and strength. Based on the current geometry of uprights for KTH Formula Student’s latest car, the eV12, new titanium uprights were designed using SolidWorks. This was done by using experience in upright design and intuition, by analysing and altering the designs in an iterative process. Three designs were made: a lighter version of the existing one, a hollow version and an unconventional version that utilises design possibilities with additive manufacturing. To verify the three different titanium designs, an analysis of the existing aluminium upright was performed. Using the results of this analysis, stiffness and maximum stress goals were set on the new titanium uprights. None of the concepts fully met the set goals, but valuable insight into design, solid mechanics and manufacturing methods was gained. The fact that specific stiffness of titanium is lower than that of aluminium means that it would be hard to make a proper design without the use of topology optimisation software, if weight is one of the most important factors. With more time, the designs would likely meet the set goals.

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