This thesis was created as a bachelor project in the Faculty of Mechanical Engineering at VUT in Brno. In the theoretical part, the additive technology Rapid Prototyping is introduced together with the most common methods, followed by the assessment of advantages and disadvantages of the new technology and its possible uses in various fields of human activity. In the experimental part of the diploma thesis was assembled and the printing parameters were set. Consequently the comparison models were printed on the 3D home printer and on professional printer Dimension uPrint. The accuracy of the printers is compared. The thesis concludes with the analysis of technical and economical parameters.

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.

Gold catalysis has become an important tool to achieve highly chemoselective p-acid activation. Exceptional reactivity and selectivity are often encountered under mild reaction conditions. These properties have made gold(I) complexes suitable catalysts for tremendous applications in the total synthesis of natural products. The first chapter will highlight a number of total syntheses using gold catalysis as a key step. The second chapter will cover our application of the gold(I)-catalyzed 6-endo-dig carbocyclization for the synthesis of bridgehead-substituted scaffolds and its use toward the synthesis of PPAP natural products. This research has opened our eyes to the utility of biphenylphosphine ligands, particularly JohnPhos, in gold(I)-catalysis. The reactivity and selectivity exhibited by gold(I) complexes is modulated by the nature of the ancillary ligand. Recent research rationalizes the impact of these ligands on the divergent reactivity observed between cationic and carbenoid intermediates. Our desire to favor the 6-endo-dig pathway has led us toward the discovery of another example of the diagonal reactivity that NHC carbene and biphenylphosphine ligands can bring to gold(I)-catalysis. Chapter three will explain the development of a selective gold-catalyzed synthesis of fused carbocycles . Our selective divergent synthesis of fused carbocycles, combined with the Diels–Alder reaction, has brought new synthetic opportunities. Chapter four will describe our approach toward the synthesis of various polycyclic diterpene-related frameworks. Starting with a unique linear precursor, we have developed a new “one-pot” process for the synthesis of three different polycyclic compounds related to the terpenoid family. The facile modulation of the linear precursor and the use of different dienophiles during the Diels–Alder reaction could enable the synthesis of diverse polycyclic analogues based on three principal frameworks. The gold(I)-catalyzed synthesis of fused carbocycles reached some limitations during our study. Regioselective control was found to be substantially more challenging, with terminal alkynes or alkynes bearing a sterically and electronically neutral methyl substituent. In chapter five, we will discuss how the complementarity of silver(I) catalysis to gold(I) catalysis enabled the selective divergent synthesis of three different fused carbocycles from a unique precursor. Moreover, copper(I) catalysis has given access to the 6-endo-dig pathway on terminal alkynes without the formation of a vinylidene intermediate.

Members of the elderly population is disproportionately prone to experiencing mobility impairment due to their aging bodies and as a result have frail bodies that are at a higher risk of grave injury due to falling. In order to combat this assistive mobility devices such as exoskeletons have been developed to help patients enhance their range of motion. With additive manufacturing techniques, such as fused deposition modeling (FDM), becoming a more mainstream form of design, the inclusion of lightweight polymers such as nylon 12 as primary construction materials for these devices has increased. In this thesis computer aided design (CAD) software was used to design a prototype lower body exoskeleton and simulation software was used to give the device the characteristics of Stratasys' nylon 12 carbon fiber FDM material to verify it if could be used as the primary construction material for this device when extruded from a FDM printer on either the XZ or ZX printing plane. From the simulations it was found that the material printed along the XZ plane could create a device that could withstand the weight of an average elderly male patient (200 lbs.) as well as the 35 lbs. of force applied to the device by a linear actuation motor that would be used to extend and contract the exoskeleton leg.

There are two sections to this research dissertation. Part one includes syntheses of fused-ring heterocycles derived from thiazole, oxazole, benzoxazole and benzothiazole derivatives and trifluoroacetylations of in situ generated N-methyl cyclic ketene-N,O/Sacetals. Attempted functionalized polymer syntheses from plant-derived 5-(hydroxymethyl) furfural are discussed in part two. Three 2-methylthiazoles, 2,4,5-trimethyloxazole, 2-methylbenzoxazole and 2- methyl-benzothiazole were each reacted with benzoyl chloride in acetonitrile/triethylamine to generate benzyl-vinyl esters. Base hydrolysis of these benzyl-vinyl esters formed 2-(heterocyclic)-1-phenylethenols which exist in both ketoenol tautomeric forms. These tautomers were used as starting materials for fused-ring heterocycle syntheses. Each tautomeric pair react with dimethyl acetylenedicarboxylate in methanol giving the 5,6-ringused 8-benzoyl-5-oxo-5H-thiazolo-, 8-benzoyl-5-oxo-5H-oxazolo-, 4-benzoyl-1-oxo-1H-benzo[4,5]oxazolo- and 4-benzoyl-1-oxo-1H-benzo[4,5]thiazolo [3,2-a]pyridinecarboxylate derivatives. Two novel 5,7-ringused 9-benzoyl-2,3- dimethyl-5,6-dihydrothiazolo- and 9-benzoyl-2,3-dimethyl-5,6-dihydrooxazolo[3,2-a] azepine-5,6,7,8-tetracarboxylates formed when the tautomers formed from 2,4,5- trimethyl thiazole and 2,4,5-trimethyl oxazole were reacted with DMADC. These tautomers react with 1,3-diacid chlorides in acetonitrile/triethylamine affording the 5,6-ringused 8-benzoyl-6,6-dialkyl-6H-thiazolo- and 8-benzoyl-6,6- dimethy-6H-oxazolo-, 4-benzoyl-2,2-dimethyl-1H-benzo[4,5]thiazolo- and 4-benzoyl- 2,2-dimethyl-1H-benzo[4,5]oxazolo[3,2,-a]pyridinedione derivatives. Functionalized 5,6- ringused 8-benzoyl-6H-thiazolo- and 8-benzoyl-6H-oxazolo[3,2]pyrimidine-5,7- diones, and 4-benzoyl-1H-benzo[4,5]thiazolo- and 4-benzoyl-1H-benzo[4,5]oxazolo[3,2- c]pyrimidine-1,3(2H)-diones formed reacting the tautomers with N-chlorocarbonyl isocyanate in THF/triethylamine. Significant ring size and substituent effects were observed in trifluoroacetylations of in situ-generated cyclic ketene-N,O/S acetals. In situ-generated 3,4,4-trimethyl-2- methylene-oxazolidine, 3-methyl-2-methylene-oxazolidine and 3-methyl-2-methylene- 1,3-oxazinane each formed β,β-bistrifluoroacetylated products. However, 3-methyl-2- methylene-oxazolidine also afforded a γ-lactam by an iodide-catalyzed rearrangement of its β,β-bistrifluoroacetylated derivative. In situ-generated 3-methyl-2-methylenethiazolidine gave both β-mono- and β,β-bistrifluoroacetylation products. 5-(Hydroxymethyl)furfural synthesized from sucrose was converted to 2,5- bis(hydroxymethyl)furan (2,5-BHMF). 7-Oxanorbornene-type Diels-Alder adducts synthesized from 2,5-BHMF were used as monomers for both ring opening metathesis polymerizations (ROMPs) and polycondensations. ROMP, followed by polycondensation or vise versa were expected to give highly functionalized cross-linked polymers. ROMP of the monomers using three Grubbs’ 1st, 2nd and 3rd generation catalysts were unsuccessful due to the presence of hydroxymethyl groups at one or both bridgeheads that could coordinate Ruthenium. With one bridgehead methyl present ROMP proceeded. Low molecular weight polyesters were synthesized via polycondensation. One was crosslinked using ROMP, but not to its gel point.

No description available.

In response to the extensive energy demands on national and global levels, concentrated solar power (CSP) plants are designed to harness and convert solar energy to electricity. For such green energy application, robust, reliable and durable materials for CSP constructions are required. The corrosion resistance is among many parameters to consider in these thermalelectrical stations such as for pipes and storage tanks in CSP. In this investigation, the corrosion behavior of AISI 304 stainless steel (18 wt. % Cr, 8 wt. % Ni) with the heat transfer fluid, also known as solar salt, has been examined. The ternary eutectic salt mixture with the composition, 53 wt. % KNO3, 40 wt. % NaNO2, and 7 wt. % NaNO3, that melts at 142°C, has a potential use in CSP as a heat transfer fluid. The solar salt was prepared for this corrosion study from reagent grades of high purity nitrites and nitrates. Samples of AISI 304 stainless steel were sectioned from a sheet stock of the alloy and exposed to solar salt at 530°C in air at 1 atmospheric pressure. After test intervals of 250, 500, and 750 hours in total immersion condition, AISI 304 stainless steel samples have developed a scale of corrosion products made up of multiple oxides. X-ray diffraction and scanning electron microscopy with X-ray energy-dispersive spectroscopy were employed to examine the extent of corrosion and identify the corrosion products. Transmission electron microscopy was used to verify the corrosion products identity via electron diffraction patterns. Oxides of iron were found to be the primary corrosion products in the presence of the molten alkali nitrates-nitrite salt mixture because of the dissolution of the protective chromium oxide (Cr2O3) scale formed on AISI 304 stainless steel coupons. The corrosion scale was uniform in thickness and made up of sodium iron oxide (NaFeO2), iron oxide, hematite (Fe2O3), and chromium-iron oxide (Cr,Fe)2O3 solid solution. The latter was iv found near the AISI 304 stainless steel. This indicates that the scale formed, particularly on the upper layers with presence of sodium iron oxide and iron oxide, hematite, is protective, and forms an effective barrier against penetration of fused solar salt. At the alloy interface with the bulk corrosion scale, the corrosion process induced a compositional modification in the grains located at the interface. There are iron rich and iron depleted grains at the interface if compared to the nominal iron content of the alloy. The mode of attack is identified as uniform at the test temperature of 530°C, showing a parabolic behavior with a parabolic rate constant (Kp) equals to (m2 /sec). By extrapolation, annual corrosion rate is estimated to reach 0.784 mils per year. Corrosion behavior of AISI 304 stainless steel is discussed in terms of thermodynamics and reaction paths.

Additive Manufacturing (AM, 3D printing) has made significant advancements over the past decade and has become a viable alternative to traditional machining techniques. AM offers several advantages over traditional manufacturing techniques including improved geometric freedom, reduction in part lead time, cost savings, enhanced customization, mass reduction, part elimination, and remote production. There are many different AM processes with the most commonly used process being Fused Filament Fabrication (FFF). Small satellites have also made significant advancements over the past two decades with the number of missions launched annually increased by orders of magnitude over that time span. Small satellites offer several advantages compared to traditional spacecraft architectures including increased access to space, lower development costs, and disaggregated architectures. On-orbit manufacturing and assembly have become major research and development topics for government and commercial entities seeking the capability to build very large structures in space. AM is well suited on-orbit manufacturing since the process is highly automated, produces little material waste, and allows for a large degree of geometric freedom. This dissertation seeks to address three major research objectives regarding applications of additive manufacturing in space systems: demonstrate the feasibility of 3D printing an ESPA class satellite using FFF, develop a FFF 3D printer that is capable of operating in high vacuum and characterize its performance, and analyze the coupled dynamics between a satellite and a robot arm used for 3D printing in-space. This dissertation presents the design, finite element analysis, dynamic testing, and model correlation of AdditiveSat, an additively manufactured small satellite fabricated using FFF. This dissertation also presents the design, analysis, and test results for a passively cooled FFF 3D printer capable of manufacturing parts out of engineering grade thermoplastics in the vacuum of space. Finally, this dissertation presents a numerical model of a free-flying small satellite with an attached robotic arm assembly to simulate 3D printing structures on-orbit with analysis of the satellite controls required to control the dynamics of the highly coupled system. / Doctor of Philosophy / 3D printing has made significant advancements over the past decade and has become common place in offices, schools, and even the homes of hobbyist. 3D printing has become an alternative to traditional machining techniques, such as machining parts from blocks of material. 3D printing offers several advantages over traditional manufacturing techniques including improved geometry freedom, reduction in part lead time, cost savings, enhanced customization, mass reduction, part elimination, and remote production. There are many different types of 3D printing with the most commonly used process being Fused Filament Fabrication (FFF) in which a thermoplastic is melded by a hotend and then extruded through a nozzle to deposited material layer-by-layer onto a printed part. Small satellites have also made significant advancements over the past two decades with the number of missions launched annually greatly increased over that time span. Small satellites offer several advantages compared to traditional spacecraft including increased access to space and lower development costs. On-orbit manufacturing and assembly have become major research and development topics for government and commercial entities seeking the capability to build very large structures in space. This dissertation seeks to address three major research objectives regarding applications of additive manufacturing in space systems: demonstrate the feasibility of 3D printing an ESPA class satellite using FFF, develop a FFF 3D printer that is capable of operating in high vacuum and characterize its performance, and analyze the coupled dynamics between a satellite and a robot arm used for 3D printing in-space. This dissertation presents the design, analysis, and test results of AdditiveSat, a 3D printed small satellite made using FFF. This dissertation also presents the development of a FFF 3D printer capable of operating in the vacuum of space. Finally, this dissertation presents a numerical simulation that models 3D printing structures on-orbit with a small satellite equipped with a robot arm.

Multi-material 3D Printing allows the ability to fabricate parts with tuned mechanical properties, multi-process 3D printing widens the choices of available fabrication materials. The objective of this study is to build a custom 3D printing test bed that is capable of printing multi-material parts with fused deposition modeling and direct ink writing techniques. A 3D printer, controlled by an industrial motion control system, with FDM and DIW capabilities was built by combining FDM extruders with a pneumatic dispensing system on a single platform. By utilizing the Direct Ink Writing function, we expand the number of printable materials to include some off the shelf silicones and epoxies, as well as custom, user made, materials. This study will further expand the manufacturing and research capabilities within the additive manufacturing discipline.

No description available.