Дисертації з теми "Laser directed energy deposition"
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Sreekanth, Suhas. "Laser-Directed Energy Deposition : Influence of Process Parameters and Heat-Treatments." Licentiate thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-15767.
Повний текст джерелаCrisanti, Roberto. "Laser Direct Energy Deposition per la manifattura additiva: caratterizzazione del processo e prove sperimentali." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Знайти повний текст джерелаJuhasz, Michael J. "In and Ex-Situ Process Development in Laser-Based Additive Manufacturing." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu15870552278358.
Повний текст джерелаLindell, David. "Process Mapping for Laser Metal Deposition of Wire using Thermal Simulations : A prediction of material transfer stability." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85474.
Повний текст джерелаAdditiv tillverkning (AT) är en kraftigt växande tillverkningsmetod på grund av sin flexibilitet kring design och möjligheten att skapa komponenter som inte är tillverkningsbara med traditionell avverkande bearbetning. AT kan kraftigt minska tid- och materialåtgång och på så sett minskas kostnader och miljöpåverkan. Införandet av AT i flyg- och rymdindustrin kräver strikt kontroll och förutsägbarhet av processen för att försäkra sig om säkra flygningar. Lasermetalldeponering av tråd är den AT metod som hanteras i denna uppsats. Användandet av tråd som tillsatsmaterial skapar ett potentiellt problem, materialöverföringen från tråden till substratet. Detta kräver att alla processparametrar är i balans för att få en jämn materialöverföring. Är processen inte balanserad syns detta genom materialöverföringsstabiliteterna stubbning och droppning. Stubbning uppkommer då energin som tillförs på tråden är för låg och droppning uppkommer då energin som tillförs är för hög jämfört med vad som krävs för en stabil process. Dessa två fenomen minskar möjligheterna för en kontrollerbar och stabil tillverkning. På grund av detta har användandet utav termiska simuleringar för att prediktera materialöverföringsstabiliteten för lasermetalldeponering av tråd med Waspaloy som deponeringsmaterial undersökts. Det har visat sig vara möjligt att prediktera materialöverföringsstabiliteten med användning av termiska simuleringar och kriterier baserat på tidigare experimentell data. Kriteriet för stubbning kontrolleras om en slutförd simulering resulterar i en tråd som når under smältan. För droppning finns två fungerande kriterier, förhållandet mellan svetshöjd och penetrationsdjup om verktygshöjden är konstant, sker förändringar i verktygshöjden är det dimensionslös ”slenderness” talet ett bättre kriterium. Genom att använda dessa kriterier är det möjligt att kvalitativt kartlägga processfönstret och skapa en bättre förståelse för förhållandet mellan verktygshöjden och den deponerade tvärsnittsarean.
Kumara, Chamara. "Microstructure Modelling of Additive Manufacturing of Alloy 718." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13197.
Повний текст джерелаPinchuk, A., and K. Jiang. "Laser-Directed Deposition of Mannan-Functionalized Silver Nanostructures." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42504.
Повний текст джерелаMcGinnis, Roger D. "Free Electron Laser development for directed energy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA387898.
Повний текст джерелаDissertation advisor, Colson, William B. "December 2000." Includes bibliographical references (p. 131-133). Also available in print.
Waller, Gordon Henry. "Template Directed Growth of Nb doped SrTiO3 using Pulsed Laser Deposition." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32723.
Повний текст джерелаMaster of Science
Williams, Robert E. "Naval electric weapons : the electromagnetic railgun and free electron laser /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FWilliams.pdf.
Повний текст джерелаKundrapu, Madhusudhan, Michael Keidar, and Charles Jones. "Electrostatic Approach for Mitigation of Communication Attenuation During Directed Energy Testing." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606128.
Повний текст джерелаElectrostatic approach is considered for mitigation of communication attenuation during the testing of laser powered directed energy weapon. Mitigation analysis is carried out for two target materials Al and Ti. Plasma parameters are obtained using one dimensional coupled analysis of laser-target interaction. Influence of laser beam frequency on plasma parameters is addressed. Sheath thickness is obtained using transient sheath calculations. It is found that uninterrupted telemetry can be achieved | using a maximum bias voltage of 10 kV, through Al plasma for fluences below 5 J/cm² and through Ti plasma for fluences below 2 J/cm².
Rajendran, Saravanakanthan, Michael Keidar, Iain D. Boyd, Charles H. Jones, and Brian Mork. "MODELING OF THE PLASMA FORMATION DUE TO LASER IRRADIENCE DURING DIRECTED-ENERGY TESTING." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604489.
Повний текст джерелаReal-time transmission of airborne images to a ground station is highly desirable in many telemetering applications. Such transmission is often through an error prone, time varying wireless channel, possibly under jamming conditions. Hence, a fast, efficient, scalable, and error resilient image compression scheme is vital to realize the full potential of airborne reconnaisance. JPEG2000, the current international standard for image compression, offers most of these features. However, the computational complexity of JPEG2000 limits its use in some applications. Thus, we present a scalable low complexity coder (SLCC) that possesses many desirable features of JPEG2000, yet having high throughput. Continuous radio-wave telemetry is required during planned tests of directed-energy weapons systems in order to characterize in situ the effects of laser irradiation on different target materials. Unfortunately, the incident radiation can cause disruption of the radio signal during the directed-energy testing. Several phenomena associated with directed-energy impact can lead to communication path losses, such as ablation, charged particle emission, charring, and chemical changes in the target materials. Directed-energy impact on the target material leads to target heating and consequent ablation. In this paper, a numerical model has been developed to describe the laser induced ablation of metal surfaces. The model describes the absorption of the laser energy by the metal and the resulting temperature rise in the surface. This temperature rise then induces ablation of the target material. Results for an aluminum target irradiated with a KrF laser were obtained. Temperature profiles in the target material and surface temperature changes are presented along with the ablation rate as a function of time as the aluminum target is irradiated. This report presents results for cases when laser energy absorption by the plasma plume created above the surface is not significant.
Balit, Yanis. "Mechanical properties of additively manufactured or repaired single-track thickness structures by Directed Energy Deposition." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX014.
Повний текст джерелаThis thesis was dedicated to the study of 316L stainless steel additively manufactured or repaired specimens by Directed Energy Deposition (DED). Different configurations were manufactured under optimal process parameters. The novelty of this work is the observation of the microstructural strain localization. This experiment combined an in situ tensile test inside a scanning electron microscope with high resolution digital image correlation and an electron backscatter diffraction map. These results allowed for a fresh interpretation of monotonic tensile tests as well as of self-heating experiments under cyclic loading and the failure patterns observed at the surface of specimens. The first objective was to understand the deformation mechanisms at the grain scale which could explain the observed macroscopic anisotropy of the tensile properties as reported in literature. Two loading directions, along and perpendicular, were considered with respect to the printing direction for fully printed specimens. We observed that for a tensile load perpendicular to the printing direction, the strain localization is mainly situated at some interlayers. For a tensile load along the printing direction, the strain localization was observed in some particular regions of large grains. The second objective was the assessment of DED as a repair technology. Dog bone shaped repaired specimens (half hot rolled sheet and half printed) were designed and they exhibited an important hierarchical microstructural gradient. We noticed that the interface is not a weak area during a monotonic tensile test. Moreover, while homogeneous strain was observed in the substrate half, the printed half showed a strain heterogeneity, with the highest localization found at some interlayers. An unstrained zone was observed at both sides of the interface and was associated with higher hardness. The last objective was to evaluate the fatigue properties by self-heating tests. The experiment has proven that the difficulties due to the small dimensions of the single-track thickness specimens can be overcome by careful construction of the experimental set-up. The results revealed a certain correlation between the pattern of the microstructure, the deformation pattern at this scale and the self-heating results. Anisotropy was highlighted during these cyclic tests where specimens tested perpendicularly to the printing direction showed higher fatigue limits in comparison to the ones tested along the printing direction. Post mortem analysis revealed a multitude of cracks at interlayers for the specimens tested perpendicularly to the printing direction creating several sites of heat diffusion. For the specimens tested along the printing direction, a more classical fatigue scenario was observed with one dominating crack and thus a localized heat dissipation
Snyder, Ryan Daniel. "Combinatorial Analysis of Thermoelectric Materials using Pulsed Laser Deposition." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1460037906.
Повний текст джерелаMantzouris, Georgios. "Thermomechanical effects of ground-based directed energy weapons on satellites and Intercontinental Ballistic Missiles." Thesis, Monterey, California. Naval Postgraduate School, 2006. http://hdl.handle.net/10945/2570.
Повний текст джерелаThermo mechanical modeling and simulation of a satellite and intercontinental ballistic missile assumes importance due to the increased interest in assessing the potential of such attacks. Effective and innovative methods are sought in assessing the structural integrity of such structural components. In this study, we present modeling and simulation aspects of two generic models loaded by high energy laser beam. We present an application of MSC software in modeling thermo-mechanical behavior, both steady state and transient behavior of satellite and missile structures. Thermal energies used for simulation correspond to high energy laser flux available at low earth orbits as reported in literature. A brief review of the concepts involved is outlined. The analysis is performed under several scenarios that include thermal failures due to steady state as well as transient thermal exposures. The thermal exposure times and locations are varied to assess typical failure modes of the structure. Analysis is done in order to define suitable material thicknesses that will make a satellite or a ballistic missile hardened enough to withstand these specific amounts of energy. Other parameters of interest pertaining to this study are the pulse width, and resulting transient phenomena affecting the behavior. Temperature gradients as well as resulting thermal stresses and thermal deformations are reported in this study.
Outstanding Thesis
Guevenoux, Camille. "Réparation de pièces métalliques par Directed Energy Deposition : gradient microstructural, comportement mécanique et tenue en fatigue." Thesis, Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAX006.
Повний текст джерелаDirected Energy Deposition (DED) process is a powder-jet additive manufacturing process involving a nozzle composed of coaxial laser beam and powder stream. The laser generates a melt pool in which the powder is projected, it melts and then solidifies creating a deposit as the nozzle moves. However, this process is particularly appealing to repair valuable metallic components. The small spot size and fast motions of the laser causes strong thermal gradient and important cooling rates and this specific thermal evolution is responsible for the formation of microstructures different from traditional processes like forge or foundry. Consequently, the repaired components exhibits an interface between the base material (generally wrought) and the region reconstructed with DED. This microstructural gradient leads to a mechanical gradient and therefore to localization phenomena which can affect the lifetime of repaired components. This thesis proposes a method to characterize the interface region of repaired components. A semi-analytic tool has been developed to model the thermal evolution during the repair process in order to design representative specimens, in terms of geometry but also in terms of thermal history. The microstructural gradient through the interface is first characterized with a SEM and EBSD analyses. Tensile specimen are then taken in the interface region and loaded during SEM in-situ tests. The strain is followed at the micrometric scale with Digital Image Correlation, what provides the information regarding localization phenomena. Those experimental data are then injected into a numerical method to identify the local parameters of the mechanical behavior by minimizing the error between the experimental and numerical fields. Using this mechanical gradient, the stress in fatigue specimens is derived. A fatigue limit is then derived from the experimental results of the fatigue tests and it is compared to the endurance of the original part to estimate the reduction of resistance caused by the repair
Collins, Peter Chancellor. "A combinatorial approach to the development of composition-microstructure-property relationships in titanium alloys using directed laser deposition." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1078949851.
Повний текст джерелаTitle from first page of PDF file. Document formatted into pages; contains xxxi, 307 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Hamish L. Fraser, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 302-316).
Mansfield, Robb P. "High energy solid state and free electron laser systems in tactical aviation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FMansfield.pdf.
Повний текст джерелаSena, S. P. "An investigation of some magnetic oxides grown by pulsed laser deposition." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287655.
Повний текст джерелаShrestha, Sulochana. "MECHANICAL CHARACTERIZATION OF Ti-6AL-4V REPAIRED BY DIRECTED ENERGY DEPOSITION IN COMPARISON WITH THE CONVENTIONAL Ti-6AL-4V." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619700926536015.
Повний текст джерелаGvozdich, Grant Gregory. "Modeling the Transient Effects of High Energy Subsystems on High-Performance Aerospace Systems." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35704.
Повний текст джерелаThe high-energy weapon system employed in this research contains power storage, power conditioning equipment, optics, and a solid-state laser. The high-energy weapon system is integrated into the aircraft by a dedicated thermal management system connected to the onboard air and fuel fluid networks. The dedicated thermal management system includes heat exchangers, thermal storage, microchannel coolers, valves, and pumps. Governing equations for the electric directed energy weapon subsystem and thermal management system are formulated for each system component and modeled in Mathworkâ s SimulinkTM. System models are integrated into a generic, high-performance aircraft model created as part of the Air Force Research Laboratoryâ s Integrated Vehicle Energy Technology Demonstration (INVENT) program. The aircraft model performs a defined mission profile, firing the directed energy weapon during the high-altitude, transonic cruise segment.
When firing a 100-kilowatt directed energy weapon system operating at 16.9% efficiency, large thermal transients quickly heat downstream onboard systems. Real-time heat rejection causes temperature spikes in avionic and environment systems that exceed allowable operation constraints. The addition of thermal storage to the thermal management system mitigates thermal impacts downstream of the directed energy weapon by delaying the time thermal loads are rejected to aircraft, thereby reducing peak and average loads. Although thermal storage is shown to mitigate peak loads in downstream onboard systems, thermal closure is yet to be achieved.
This research presents a general and fundamental approach to investigating the thermal impacts of a directed energy weapon system on a high-performance aircraft. Although specific
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cases are analyzed, this general approach to model development and simulation is conducive to component and system customization for many other cases. Additionally, the supplementation of models with analytical, semi-empirical, and empirical data further tailors model development to each userâ s need while increasing the potential to enhance accuracy and efficacy. Without the material expenses of a â plug-and-checkâ method, component and system level modeling of the directed energy weapon system and high-performance aircraft provides valuable insight into the thermal responses of highly-coupled systems.
Master of Science
Allgaier, Gregory G. "The shipboard employment of a free electron laser weapon system." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FAllgaier.pdf.
Повний текст джерелаThesis advisor(s): William Colson, Robert Armstead. Includes bibliographical references (p. 67-68). Also available online.
Chanal, Margaux. "Space-time study of energy deposition with intense infrared laser pulses for controlled modification inside silicon." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0488/document.
Повний текст джерелаThe modification of bulk-silicon is realized today with infrared nanosecond lasers. However, the interest regime for controlled modifications inside transparent materials is femtosecond pulses. Today, there is no demonstration of a permanent modification in bulk-Si with ultra-short laser pulses (100 fs). To increase our knowledge on the interaction between femtosecond lasers and silicon, we have developedultra-fast infrared microscopy experiments. First, we characterize the microplasma confined inside the bulk, being the generation of free-carriers under nonlinear ionization processes, followed by the complete relaxation of the material. These results, combined with the reconstruction of the beam propagation inside silicon, demonstrate that the energy deposition is strongly limited by nonlinear absorption andpropagation effects. This analysis has been confirmed by a numerical model simulating the nonlinear propagation of the femtosecond pulse. The understanding of this clamping has allowed us the development of new experimental arrangements, leading to the modification of the bulk of Si with short pulses
Point, Guillaume. "Energy deposition in air from femtosecond laser filamentation for the control of high voltage spark discharges." Palaiseau, Ecole polytechnique, 2015. https://tel.archives-ouvertes.fr/tel-01202982/document.
Повний текст джерелаLaser filamentation is a spectacular optical propagation regime appearing for pulses of which peak power exceeds a few GW in air. Filament forms due to the optical Kerr effect, which tends to self-focus the beam until intensity reaches the medium ionization threshold by multiphoton absorption. A complex dynamic competition is then established between the Kerr effect on the one hand, and diffraction, nonlinear absorption and plasma defocusing effect on the other hand. This results in a reorganization of the beam profile, characterized by a thin (100 µm) and intense (10^18 W/m²) core able to propagate over a distance much longer than the Rayleigh length. When the initial pulse peak power largely exceeds filamentation threshold, several co-propagating filaments are formed in the same beam, with each of these multifilaments sharing physical properties of isolated single filaments. While propagating in air, filaments transfer a portion of the laser energy to the medium, mainly through Raman rotational excitation of air molecules, ionization and inverse Bremsstrahlung in the plasma. This energy is redistributed in one nanosecond and almost entirely converted into air molecule translational energy, that is heat. The medium reacts to this rapid heating by launching a cylindrical pressure wave that brings the system back to pressure equilibrium by ejecting matter from the center. This results in the formation of a hot underdense air channel, which slowly resorbs by diffusion at timescales > 1 ms. My work as a Ph. D. Student first focused on the study and the optimization of laser energy deposition in air by filamentation. Thus, I investigated the influence of laser parameters such as pulse energy, focusing strength or pulse duration on deposited energy. To this purpose, I used several complementary diagnostics: study of pressure waves using microphones, characterization of the filamentation plasma by means of spectroscopy and time resolved study of underdense air channels using interferometry. I demonstrated in the single filamentation regime that above a given pulse energy, energy deposition becomes so important that the medium generates a shock wave instead of a sound wave, and that underdense channels can last for more than 100 ms. I also studied and characterized the high energy multifilamentation regime, showing that moderately focusing the pulse leads to a reorganization of filaments in the focal zone, generating large structures with a resulting plasma ten times denser than filaments. Filamentation-induced hydrodynamic effects lead to a transient reduction of the air breakdown voltage along the path of the laser pulse, enabling one to trigger and guide electric discharges. The second part of my thesis focused on the study and the optimization of such guided discharges for the design of a radio-frequency plasma antenna, contactless high-voltage switches or a laser lightning rod. To this purpose I developed and built an interferometric plasma diagnostic, allowing to measure the lifetime of generated plasmas. I also contributed to the proof of principle for a filament induced plasma antenna emitting RF signal. Finally, I took part to prospective experimental studies for the development of a laser lightning rod
Kawwam, Mohammad. "Pulsed Laser Deposition and Structural Analysis of Crystalline CuO and GaN Thin Films." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10007.
Повний текст джерелаThe thesis presents experimental results related to the Pulsed Laser Deposition (PLD) of GaN and CuO thin films using sapphire, SrTiO3, quartz and MgO substrates. The evolution of crystallization and surface morphology of the as-deposited films were studied to investigate the influence of the process conditions such as: substrate heating, background pressure, target-substrate distance, laser energy density, and substrate location, which were systematically varied. The as-deposited films were characterized by X-ray diffraction, atomic force microscopy and scanning electron microscopy, X-ray photoelectron spectroscopy, RHEED and RAMAN techniques. The results convincingly demonstrate that the enhancement in film growth quality - the reduction in roughness and the delay of epitaxial breakdown - is related to the control of PLD species kinetics. The films thickness, crystallinity, homogeneity and surface roughness are strongly dependent on deposition conditions
Limbach, Christopher M. "Characterization of nanosecond, femtosecond and dual pulse laser energy deposition in air for flow control and diagnostic applications." Thesis, Princeton University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3737448.
Повний текст джерелаThe non-resonant heating of gases by laser irradiation and plasma formation has been under investigation since the development of 100 megawatt peak power, Q-switched, nanosecond pulse duration lasers and the commensurate discovery of laser air sparks. More recently, advances in mode-locking and chirped pulse amplification have led to commercially available 100 gigawatt peak power, femtosecond pulse duration lasers with a rapidly increasing number of applications including remote sensing, laser spectroscopy, aerodynamic flow control, and molecular tagging velocimetry and thermometry diagnostics. This work investigates local energy deposition and gas heating produced by focused, non-resonant, nanosecond and femtosecond laser pulses in the context of flow control and laser diagnostic applications.
Three types of pulse configurations were examined: single nanosecond pulses, single femtosecond pulses and a dual pulse approach whereby a femtosecond pre-ionizing pulse is followed by a nanosecond pulse. For each pulse configuration, optical and laser diagnostic techniques were applied in order to qualitatively and quantitatively measure the plasmadynamic and hydrodynamic processes accompanying laser energy deposition. Time resolved imaging of optical emission from the plasma and excited species was used to qualitatively examine the morphology and decay of the excited gas. Additionally, Thomson scattering and Rayleigh scattering diagnostics were applied towards measurements of electron temperature, electron density, gas temperature and gas density.
Gas heating by nanosecond and dual pulse laser plasmas was found to be considerably more intense than femtosecond plasmas, irrespective of pressure, while the dual pulse approach provided substantially more controllability than nanosecond pulses alone. In comparison, measurements of femtosecond laser heating showed a strong and nonlinearly dependence on focusing strength. With comparable pulse energy, measurements of maximum temperature rise ranged from 50K to 2000K for 500mm and 175mm focal length lenses, respectively. Experiments with various lens and pulse energy combinations indicated an important connection between gas heating and the phenomena of intensity clamping and self-guiding. The long-term behavior of the heated region varied considerably among pulse configurations. However, in each case, the formation of a toroidal vortex could be suppressed or enhanced depending on the variables of pressure, focusing and pulse energy.
Bernhard, John Michael. "Work Function Study of Iridium Oxide and Molybdenum Using UPS and Simultaneous Fowler-Nordheim I-V Plots with Field Emission Energy Distributions." Thesis, University of North Texas, 1999. https://digital.library.unt.edu/ark:/67531/metadc2211/.
Повний текст джерелаAcharya, Krishna Prasad. "Photocurrent Spectroscopy of CdS/Plastic, CdS/Glass, and ZnTe/GaAs Hetero-pairs Formed with Pulsed-laser Deposition." Bowling Green State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1245089031.
Повний текст джерелаMitchell, Ethan D. "Multiple beam directors for naval free electron laser weapons." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FMitchell.pdf.
Повний текст джерелаDaugherty, Timothy J. "Assessment of the ballistic performance of compositional and mesostructural functionally graded materials produced by additive manufacturing." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1596474811965998.
Повний текст джерелаTai-YuChiu and 邱泰育. "Effect of Laser Power on Mechanical Properties and Microstructure of 316L Stainless Steel Deposited by Direct Energy Deposition(DED)." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/djmpx4.
Повний текст джерела國立成功大學
材料科學及工程學系
107
Laser power is the most directly relevant process parameter affecting the quality in Direct Energy Deposition (DED) process. In this study, we investigated laser power effect on mechanical properties and microstructure of multi-layer products after vertical deposition of 40 layers using 316L stainless steel powder. The mechanical properties were analyzed by three-point bending test combined with digital image correlation (DIC) to obtain strain distribution. The microstructure under tensile, compressive stress and neutral regions were analyzed by EBSD. Considering laser power from 800 W to 2000 W, 800 W has the highest yield stress of 476 MPa and 1600 W the lowest yield stress of 407 MPa due to coarsening effect. By analyzing strain distribution and Schmid factor, 2000 W shows low strain value and low value of Schmid factor resulting in increasing yield stress of 454 MPa.
Hsin-WeiHuang and 黃信瑋. "Numerical Modeling on Multi-layer Scanning of Directed Energy Deposition Using Stainless Steel 316L and Thermal Analysis for the Effects and Optimization of Process Parameters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/anqc4m.
Повний текст джерела國立成功大學
機械工程學系
106
In this research, a numerical model for multi-layer scanning of Directed Energy Deposition (DED) process for SS316L is constructed to study transient thermal phenomenon under primary process parameters. The geometrical sizes and cooling rate of multi-layer metal thin layers are investigated under various combination of laser power and scanning speed. It is discovered that the layer height will increase with layer number when maintaining the same process parameters. Moreover, judged from the view of time-saving, energy-saving and reducing cooling rate, the optimal combination of process parameters is determined. Furthermore, in order to obtain superior deposition appearance, the trends of reducing laser power for each layer are proposed. It is found that laser power of 1800 W and scanning speed of 8 mm/s are the optimal combination of process parameters, which is most beneficial for time saving, energy saving, promoting the growth of columnar grains and reducing cracking possibility. To further improve the manufacturing problems induced by thermal field, the effects of idle time, substrate preheating and scanning direction are studied. Results indicate that idle time has no obvious effects on process. Substrate preheating could increase geometrical sizes of metal thin layers, and obviously reduce cooling rate and temperature gradient. The single scanning direction is helpful for maintaining the conformity of deposition appearance.
Min-XuanJiang and 蔣旻軒. "Numerical Modeling on Multi-layer Scanning of Directed Energy Deposition Using Inconel 718 Superalloy and Thermal Analysis for the Effects and Optimization of Process Parameters." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/hk548g.
Повний текст джерелаLoureiro, Maria João Grilo. "Off-line robot programming for metal additive manufacturing using robot external axis." Master's thesis, 2020. http://hdl.handle.net/10316/92243.
Повний текст джерелаRobotics is destined to become the supporting technology that promotes the connection between the digital and the physical world. In an extremely competitive industrial environment, automated manufacturing is a key factor for any operation that seeks maximum efficiency, safety, and competitiveness. Despite its convenience, for certain functions, a robot is limited by its own axis system. The introduction of a coordinated system, with the external axis, allows flexibility and expansion of the robot's work zone in companies production lines.This thesis comprises the manipulation of external axes of a robotic cell applied to additive manufacturing. Offline programming methods are used in a virtual environment to assist the construction of an aircraft engine part using one of the direct energy deposition methods. The work carried out was focused on the production of a particular feature of an aircraft engine part, denominated here as Rim Part, which was initially tested on the RoboDK simulation software. During the tests, it was possible to conclude that the proposed impositions presented strong barriers to their production and for these reasons, it was necessary to change the approach, using macro programming, in C# language, to improve the coordinated movements between robots. With this method, simultaneously with the generated graphic interface, the production of the requested part was visualized, thus obtaining a very satisfactory result and without collisions between the two robots.
A robótica está destinada em tornar-se a tecnologia de suporte que promove a ligação entre o mundo digital e o físico. No meio industrial extremamente competitivo, a manufatura automatizada é um fator chave para qualquer operação que procure máxima eficiência, segurança e competitividade. Apesar da sua conveniência, para certas funções, um robô por si só é limitado pelo seu próprio sistema de eixos. A introdução de um sistema coordenado, com eixos externos, permite flexibilizar e expandir a zona de trabalho do robô nas linhas de produção das empresas. Esta tese compreende a aplicação de eixos externos num robô em manufatura aditiva e diferentes métodos de programação off-line num ambiente virtual, com o objetivo de auxiliar a construção de uma peça de um motor de avião utilizando um dos métodos de deposição direta de energia apresentados. O trabalho realizado foi focado na produção de uma feature em particular, designada por Rim Part, que inicialmente foi testado no software de simulação RoboDK. No decorrer dos ensaios, permitiu-se concluir que as imposições propostas apresentavam fortes barreiras à sua produção e por estes motivos, foi necessário mudar de abordagem recorrendo-se à programação de macros, em linguagem C#, para permitir os movimentos coordenados entre robôs. Com este método, juntamente com a interface gráfica gerada, foi possível a visualização da produção da parte requerida obtendo-se assim, um resultado bastante satisfatório e sem colisões entre os dois robôs.
Maciel, Duarte de Araújo. "Fatigue behaviour of Inconel 625 produced by Directed Energy Deposition." Master's thesis, 2021. https://hdl.handle.net/10216/134949.
Повний текст джерелаMaciel, Duarte de Araújo. "Fatigue behaviour of Inconel 625 produced by Directed Energy Deposition." Dissertação, 2021. https://hdl.handle.net/10216/134949.
Повний текст джерелаChang, Hung-Yu, and 張弘諭. "Finite Element Analysis of Thermal Effect on Directed Energy Deposition." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/vffw77.
Повний текст джерела國立高雄科技大學
機械工程系
107
In this study, the displacement behavior of SUS316L stainless steel under five-layer continuous direct energy deposition was investigated by using experiment and commercial finite element method software ANSYS, and the displacement effects of five-layer deposit were discussed after cooling. In addition, the relationship between laser power and laser feed rate under different curvatures is discussed. First, the full-section morphology was obtained by experimental method and the parameters of laser power 300W, 400W, 500W and laser feed rates of 3mm/s, 5mm/s, 7mm/s were used to simulate using thermal-structure interaction mode. The results show that the optimal preheating temperature during the deposition process is about 150 °C, and the displacement gap will be relatively stable. The effect of curvature on displacement is indistinguishable on the neutral axis, the displacement of the height can be predicted by the straight path. However, the inner and outer circles need additional experiments or finite element analysis to predict. The results show that low laser power and high feed rate in the deposition are preferable in consideration of displacement.
Rodrigues, Rui Pedro Teixeira. "Teste e Caracterização de Peças Metálicas Produzidas por Directed Energy Deposition." Master's thesis, 2018. https://hdl.handle.net/10216/116520.
Повний текст джерелаRodrigues, Rui Pedro Teixeira. "Teste e Caracterização de Peças Metálicas Produzidas por Directed Energy Deposition." Dissertação, 2018. https://repositorio-aberto.up.pt/handle/10216/116520.
Повний текст джерелаDuarte, Valdemar Rebelo. "Developments in Directed Energy Deposition Additive Manufacturing: In-situ Hot Forging and Indirect Cooling." Doctoral thesis, 2022. http://hdl.handle.net/10362/134198.
Повний текст джерелаA tecnologia de deposição direta de energia por arco (DED-arc) tem competido com outras tecnologias de fabrico aditivo devido à sua elevada taxa de deposição, capacidade de produzir componentes de grandes dimensões com média/alta complexidade geométrica e baixos custos de implementação e funcionamento. Contudo, as elevadas tensões residuais, as microestruturas grosseiras, ou os defeitos do tipo poros, podem comprometer algumas aplicações industriais e necessitam de ser superados. Este trabalho visou desenvolver e validar duas variantes inovadoras de processo DED- arc: uma baseada no forjamento a quente; e outra no controlo de temperatura. A variante baseada no forjamento, consistiu em forjar o material depositado imediatamente após a deposição, utilizando baixas forças. O objetivo foi a produção de uma zona de deformação plástica uniforme ao longo de cada camada, para promover alterações microestruturais, nomeadamente o refinamento dos grãos e a redução da anisotropia. A variante baseada no trabalho termodinâmico consistiu em arrefecer os componentes do martelo e o gás utilizado para proteger o banho de fusão, com o objetivo de aumentar a taxa de arrefecimento e assim evitar a coalescência dos grãos. Neste sentido, foi concebido e fabricado um equipamento de DED-arc, com características específicas para investigação. O efeito do forjamento a quente foi estudado detalhadamente no aço inoxidável 316LSi, e foi verificada a viabilidade da sua aplicação noutros materiais relevantes industrialmente. Concluiu-se que o forjamento induz recristalização dinâmica, aumenta os pontos de nucleação e impede o crescimento de grãos epitaxiais, contribuindo para uma microestrutura globalmente mais fina, homogénea e com melhores propriedades mecânicas. O sistema de arrefecimento desenvolvido baixou a temperatura do bocal e do martelo durante as deposições consecutivas. O arrefecimento do gás de proteção não teve efeito nas taxas de arrefecimento nem na microestrutura do material, contudo, observou-se que o forjamento altera as condições de fluxo de calor, promovendo taxas de arrefecimento maiores.
Cooke, Shaun. "Numerical modelling and metallurgical characterization of Cr-Mo steels processed by directed energy deposition." Thesis, 2021. http://hdl.handle.net/1828/13103.
Повний текст джерелаGraduate
2022-07-05
Abutaha, Anas I. "Nanostructured Thermoelectric Oxides for Energy Harvesting Applications." Diss., 2015. http://hdl.handle.net/10754/583286.
Повний текст джерелаCheng-HungChu and 居正宏. "Numerical Modeling on Directed Energy Deposition for Stainless Steel 316L and Thermal Analysis of the Effects of Process Parameter." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/fw2m2d.
Повний текст джерелаSeca, Ricardo João Martins. "Desenvolvimento de técnicas de reparação de peças por fabrico aditivo através da tecnologia de Directed Energy Deposition (DED) - Aços Maraging." Master's thesis, 2021. https://hdl.handle.net/10216/136750.
Повний текст джерела"Pulsed Laser Deposition of Highly Conductive Transparent Ga-doped ZnO for Optoelectronic Device Applications." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.8868.
Повний текст джерелаDissertation/Thesis
Ph.D. Materials Science and Engineering 2011
Höfer, Kevin. "Qualifizierung des Plasma-Pulver-Auftragschweißprozesses für die generative Herstellung von Bauteilen der Legierung 1.4404." 2020. https://monarch.qucosa.de/id/qucosa%3A74064.
Повний текст джерелаAdditive manufacturing is one of the key technologies of the future for large parts of the economy. The process of plasma powder deposition welding is intended to close a gap in the existing portfolio of generative processes. First, the classical cladding process was adapted to the requirements of additive manufacturing. As a result, components, which can consist of up to four different materials, could be reliably generated. The subsequent consideration of the influence of the system parameters on the component showed that the main influencing variables on the part geometry are the welding current, the welding speed, the powder flow rate and the plasma gas volume. The component density as well as the powder utilization rate show no significant changes within the range considered here. On average, a relative component density of 98.7 % and a material utilization rate of 77 % could be determined. In sum, the process can be characterized by a stable application characteristic with at least comparable properties to existing systems and is very well suitable as an additive manufacturing process, especially for the production of multi material components.
Sunil, Maligi Anantha. "Studies on AgInS2 Films as Absorber Layer for Heterojunction Solar Cells." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2818.
Повний текст джерела