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Qualification of Metal Additive Manufacturing in Space Industry : Challenges for Product DevelopmentDordlofva, Christo January 2018 (has links)
Additive manufacturing (AM), or 3D printing, is a collection of production processes that has received a good deal of attention in recent years from different industries. Features such as mass production of customised products, design freedom, part consolidation and cost efficient low volume production drive the development of, and the interest in, these technologies. One industry that could potentially benefit from AM with metal materials is the space industry, an industry that has become a more competitive environment with established actors being challenged by new commercial initiatives. To be competitive in these new market conditions, the need for innovation and cost awareness has increased. Efficiency in product development and manufacturing is required, and AM is promising from these perspectives. However, the maturity of the AM processes is still at a level that requires cautious implementation in direct applications. Variation in manufacturing outcome and sensitivity to part geometry impact material properties and part behaviour. Since the space industry is characterised by the use of products in harsh environments with no room for failure, strict requirements govern product development, manufacturing and use of space applications. Parts have to be shown to meet specific quality control requirements, which is done through a qualification process. The purpose of this thesis is to investigate challenges with development and qualification of AM parts for space applications, and their impact on the product development process. Specifically, the challenges with powder bed fusion (PBF) processes have been in focus in this thesis. Four studies have been carried out within this research project. The first was a literature review coupled with visits to AM actors in Sweden that set the direction for the research. The second study consisted of a series of interviews at one company in the space industry to understand the expectations for AM and its implications on product development. This was coupled with a third study consisting of a workshop series with three companies in the space industry. The fourth study was an in-depth look at one company to map the qualification of manufacturing processes in the space industry, and the challenges that are seen for AM. The results from these studies show that engineers in the space industry work under conditions that are not always under their control, and which impact how they are able to be innovative and to introduce new manufacturing technologies, such as AM. The importance of product quality also tends to lead engineers into relying on previous designs meaning incremental, rather than radical, development of products is therefore typical. Furthermore, the qualification of manufacturing processes relies on previous experience which means that introducing new processes, such as AM, is difficult due to the lack of knowledge of their behaviour. Two major challenges with the qualification of critical AM parts for space applications have been identified: (i) the requirement to show that critical parts are damage tolerant which is challenging due to the lack of understanding of AM inherent defects, and (ii) the difficulty of testing parts in representative environments. This implies that the whole product development process is impacted in the development and qualification of AM parts; early, as well as later stages. To be able to utilise the design freedom that comes with AM, the capabilities of the chosen AM process has to be considered. Therefore, Design for Manufacturing (DfM) has evolved into Design for Additive Manufacturing (DfAM). While DfAM is important for the part design, this thesis also discusses its importance in the qualification of AM parts. In addition, the role of systems engineering in the development and qualification of AM parts for space applications is highlighted.
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Improving Fatigue Life of LENS Deposited Ti-6Al-4V through Microstructure and Process ControlPrabhu, Avinash W. 02 June 2014 (has links)
No description available.
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Design for Manufacturing and Topology Optimization in Additive ManufacturingRanjan, Rajit 08 September 2015 (has links)
No description available.
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Developing Robot assisted Plastic 3D Printing PlatformKHAN, FAHAD AHMAD January 2021 (has links)
This project was initiated by Dr. Sasan Dadbaksh upon listening to the requirements I presented for my master thesis. My requirements were to do a master thesis project in the field of additive manufacturing specifically fused deposition modeling that should not only involve the research work but should also present an opportunity to develop hardware and should involve experimental testing. Then Sasan came up with the idea of developing a system capable to perform 3D printing with the extruder fixed in one position and the motion required for 3D printing will be provided by the robotic arm. The title of developing green build strategies for robot assisted plastic 3D printing came into being. The main concept behind the title of developing robot assisted plastic 3D printing platform is to develop such a system that can offer additive manufacturing services, specifically of fused deposition modeling 3D printing, as an inbound process during the manufacturing of any part through subtractive processes with the help of a robotic arm along with the repair of any kind of parts with the assistance of fused deposition modeling 3D printing. The main objectives of the master thesis include building a stationary filament extrusion module to interact with a robot hand and establishing a strategy for a robot hand to move the part to appropriate locations to complete building a part on a preform without support structures. The targets that were achieved with the completion of this thesis project includes the development of the complete hardware that consists of a mechanical structure with the option of mounting the components required to run the extrusion setup, learning the basic working of the software that are able to simulate the 3D printing process with the robotic arm (Robot Studio and Robo DK), creation of the simulation of the whole process, achieving communication between the robotic arm and the microcontroller of the extruder and finally the printing of a simple part for the demonstration. The components needed to be installed on the structure includes the motor, extruder, hot end, nozzle, filament. The structure also accumulated the required electronics that includes power supply, microcontroller, and an LCD to monitor the extrusion parameters. The developed machine runs on the state-of-the-art components that belong to the few of the best manufacturers of the technology.
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Design for Additive Manufacturing Considerations for Self-Actuating Compliant Mechanisms Created via Multi-Material PolyJet 3D PrintingMeisel, Nicholas Alexander 09 June 2015 (has links)
The work herein is, in part, motivated by the idea of creating optimized, actuating structures using additive manufacturing processes (AM). By developing a consistent, repeatable method for designing and manufacturing multi-material compliant mechanisms, significant performance improvements can be seen in application, such as increased mechanism deflection. There are three distinct categories of research that contribute to this overall motivating idea: 1) investigation of an appropriate multi-material topology optimization process for multi-material jetting, 2) understanding the role that manufacturing constraints play in the fabrication of complex, optimized structures, and 3) investigation of an appropriate process for embedding actuating elements within material jetted parts. PolyJet material jetting is the focus of this dissertation research as it is one of the only AM processes capable of utilizing multiple material phases (e.g., stiff and flexible) within a single build, making it uniquely qualified for manufacturing complex, multi-material compliant mechanisms. However, there are two limitations with the PolyJet process within this context: 1) there is currently a dearth of understanding regarding both single and multi-material manufacturing constraints in the PolyJet process and 2) there is no robust embedding methodology for the in-situ embedding of foreign actuating elements within the PolyJet process. These two gaps (and how they relate to the field of compliant mechanism design) will be discussed in detail in this dissertation. Specific manufacturing constraints investigated include 1) "design for embedding" considerations, 2) removal of support material from printed parts, 3) self-supporting angle of surfaces, 4) post-process survivability of fine features, 5) minimum manufacturable feature size, and 6) material properties of digital materials with relation to feature size. The key manufacturing process and geometric design factors that influence each of these constraints are experimentally determined, as well as the quantitative limitations that each constraint imposes on design. / Ph. D.
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Modeling Material Microstructure and Fatigue Life of Metal Components Produced by Laser Melting Additive ProcessChun-Yu Ou (8791262) 12 October 2021 (has links)
<p>There
has been a long-standing need in the marketplace for the economic production of
small lots of components that have complex geometry. A potential solution is
additive manufacturing (AM). AM is a manufacturing process that adds material
bottom-up. It has the distinct advantages of low preparation cost and high geometric
creation capability. Components fabricated via AM are now being selectively
used for less-demanding applications in motor vehicles, consumer products,
medical products, aerospace devices, and even some military projects.</p><p><br></p>
<p>For engineering
applications, high value-added components require consistency in the fatigue
properties. However, components fabricated by AM have large variation in the
fatigue properties compared to those by conventional manufacturing processes. To
alleviate unpredictable catastrophic failures of components, it is essential to
study and predict fatigue life. Previous study reported that fatigue crack
initiation process accounts for a large portion of fatigue life, especially for
low loading amplitude and high cycle fatigue. However, this major portion of
fatigue life prediction is mostly ignored by main stream researchers working on
fatigue modeling. For industrial applications, engineers often specify a lower
stress condition to obtain a higher safety factor. Under these circumstances,
fatigue crack initiation becomes even more important, so it is essential to further
study of crack initiation.</p><p><br></p>
<p>The
objective of this research is to develop a fatigue crack initiation model for
metal components produced by AM. To improve life prediction accuracy, the model
must incorporate the effect of different microstructures, which are typically
produced by AM due to a large number of repetitive cycles of re-heating and re-cooling
processes. To fulfill this objective, the tasks are separated into three studies:
(1) developing a temperature model to simulate temperature history, (2) modeling
the component’s microstructure for the potential crack initiation zone, and (3)
developing a fatigue crack initiation model for life estimation. A summary of
each task is provided in the following.</p>
<p>First,
the role of temperature model is to understand the mechanism that leads to the
variation of microstructures. The existing temperature models are
computationally expensive to obtain an accurate prediction of the temperature
history due to repetitive heating and cooling. The main reason is that these
models considered entire boundary conditions of all the material points. In
this section, we proposed and employed the concept of effective computation zone,
which can save the computational time significantly for AM process. </p><p><br></p>
<p>Second,
it is critical to include the effect of microstructure in the fatigue life
model since the microstructure variation at different locations within the real
AM component is large. The grain size variation is modeled by using representative
volume element, which is defined as a volume of heterogeneous material that is
sufficiently large to be statistically representative of the real component’s
microstructure. Regarding phase transformation, a continuous cooling
transformation (CCT) diagram is a useful tool that can be used with a thermal
model for microstructure design and manufacturing process control. However,
traditional CCT diagrams are developed based on slow and monotonic cooling
processes such as furnace cooling and air cooling, which are greatly different
from the repetitive heating and cooling processes in AM. In this study, a new
general methodology is presented to create CCT diagrams for materials
fabricated by AM. We showed that the effect of the segmented duration within
the critical temperature range, which induced precipitate formation, could be
cumulative. </p><p><br></p>
<p>Third, the
existing fatigue crack initiation life model has poor accuracy. One of the reasons
for the poor accuracy is the coefficients change due to the variation in
microstructure is not accounted for. In this section, a semi-empirical fatigue
crack initiation model is presented. The important coefficients include maximum
persistent slipband width, energy efficiency coefficient, resolved shear stress
and plastic slip rate per cycle. These coefficients are modeled and determined
as a function of microstructure, which can improve the accuracy of life
estimation.</p><p><br></p>
<p>The contribution
of this study is to provide a new engineering tool for designing the melting AM
process based on scientific research. With this tool, the fundamental mechanism
contributing to a large variation of the fatigue life of the metal components
made by AM process can be understood, attributed, predicted and improved. The seemly
‘stochastic’ nature of fatigue life of the AM components can be changed to be
more deterministic and predictable. This approach represents a major advance in
fatigue research on AM materials. The model
developed is considered as a tool for research, design, and control for
laser-based AM process applications. </p>
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FUSION BONDING OF FIBER REINFORCED SEMI-CRYSTALLINE POLYMERS IN EXTRUSION DEPOSITION ADDITIVE MANUFACTURINGEduardo Barocio (5929505) 16 January 2020 (has links)
<p>Extrusion deposition additive manufacturing (EDAM)
has enabled upscaling the dimensions of the objects that can be additively
manufactured from the desktop scale to the size of a full vehicle. The EDAM
process consists of depositing beads of molten material in a layer-by-layer
manner, thereby giving rise to temperature gradients during part manufacturing.
To investigate the phenomena involved in EDAM, the Composites Additive
Manufacturing Research Instrument (CAMRI) was developed as part of this
project. CAMRI provided unparalleled flexibility for conducting controlled
experiments with carbon fiber reinforced semi-crystalline polymers and served
as a validation platform for the work presented in this dissertation. </p>
<p>Since the EDAM process is
highly non-isothermal, modeling heat transfer in EDAM is of paramount
importance for predicting interlayer bonding and evolution of internal stresses
during part manufacturing. Hence, local heat transfer mechanisms were
characterized and implemented in a framework for EDAM process simulations.
These include local convection conditions, heat losses in material compaction
as well as heat of crystallization or melting. Numerical predictions of the
temperature evolution during the printing process of a part were in great
agreement with experimental measurements by only calibrating the radiation
ambient temperature. </p>
In
the absence of fibers reinforcing the interface between adjacent layers, the
bond developed through the polymer is the primary mechanisms governing the
interlayer fracture properties in printed parts. Hence, a fusion bonding model was
extended to predict the evolution of interlayer fracture properties in EDAM
with semi-crystalline polymer composites. The fusion bonding model was
characterized and implemented in the framework for EDAM process simulation.
Experimental verification of numerical predictions obtained with the fusion
bonding model for interlayer fracture properties is provided. Finally, this
fusion bonding model bridges the gap between processing conditions and
interlayer fracture properties which is extremely valuable for predicting
regions with frail interlayer bond within a part.
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Investigating the Ability to Preheat and Ignite Energetic Materials Using Electrically Conductive MaterialsMarlon D Walls Jr. (9148682) 29 July 2020 (has links)
<div>The work discussed in this document seeks to integrate conductive additives with energetic material systems to offer an alternative source of ignition for the energetic material. By utilizing the conductive properties of the additives, ohmic heating may serve as a method for preheating and igniting an energetic material. This would allow for controlled ignition of the energetic material without the use of a traditional ignition source, and could also result in easier system fabrication.</div><div>For ohmic heating to be a viable method of preheating or igniting these conductive energetic materials, there cannot be significant impact on the energetic properties of the energetic materials. Various mass solids loadings of graphene nanoplatelets (GNPs) were mixed with a reactive mixture of aluminum (Al)/polyvinylidene fluoride (PVDF) to test if ohmic heating ignition was feasible and to inspect the impact that these loadings had on the energetic properties of the Al/PVDF. Results showed that while ohmic heating was a plausible method for igniting the conductive energetic samples, the addition of GNPs degraded the energetic properties of the Al/PVDF. The severity of this degradation was minimized at lower solids loadings of GNPs, but this consequently resulted in larger voltage input requirements to ignite the conductive energetic material. This was attributable to the decreased conductivities of the samples at lower solids loading of GNPs.</div><div>In hopes of conserving the energetic properties of the Al/PVDF while integrating the conductive additives, additive manufacturing techniques, more specifically fused filament fabrication, was used to print two distinct materials, Al/PVDF and a conductive composite, into singular parts. A CraftBot 3 was used to selectively deposit Conductive Graphene PLA (Black Magic) filament with a reactive filament comprised of a PVDF binder with 20% mass solids loadings of aluminum. Various amounts of voltage were applied to these conductive energetic samples to quantify the time to ignition of the Al/PVDF as the applied voltage increased. A negative correlation was discovered between the applied voltage and time to ignition. This result was imperative for demonstrating that the reaction rate could be influenced with the application of higher applied voltages.</div><div>Fused filament fabrication was also used to demonstrate the scalability of the dual printed conductive energetic materials. A flexural test specimen made of the Al/PVDF was printed with an embedded strain gauge made of the Black Magic filament. This printed strain gauge was tested for dual purposes: as an igniter and as a strain sensor, demonstrating the multi-functional use of integrating conductive additives with energetic materials.</div><div>In all, the experiments in this document lay a foundation for utilizing conductive additives with energetic materials to offer an alternative form of ignition. Going forward, ohmic heating ignition may serve as a replacement to current, outdated methods of ignition for heat sensitive energetic materials.</div>
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ADDITIVE MANUFACTURING OF VISCOUS MATERIALS: DEVELOPMENT AND CHARACTERIZATION OF 3D PRINTED ENERGETIC STRUCTURESMonique McClain (9178199) 28 July 2020 (has links)
<p>The performance of solid rocket
motors (SRMs) is extremely dependent on propellant formulation, operating
pressure, and initial grain geometry. Traditionally, propellant grains are cast
into molds, but it is difficult to remove the grains without damage if the geometry
is too complex. Cracks or voids in propellant can lead to erratic burning that
can break the grain apart and/or potentially overpressurize the motor. Not only
is this dangerous, but the payload could be destroyed or lost. Some geometries
(i.e. internal voids or intricate structures) cannot be cast and there is no
consistent nor economical way to functionally grade grains made of multiple propellant
formulations at fines scales (~ mm) without the risk of delamination between
layers or the use of adhesives, which significantly lower performance. If one
could manufacture grains in such a way, then one would have more control and
flexibility over the design and performance of a SRM. However, new
manufacturing techniques are required to enable innovation of new propellant
grains and new analysis techniques are necessary to understand the driving
forces behind the combustion of non-traditionally manufactured propellant.</p>
<p>Additive manufacturing (AM) has
been used in many industries to enable rapid prototyping and the construction
of complex hierarchal structures. AM of propellant is an emerging research area,
but it is still in its infancy since there are some large challenges to
overcome. Namely, high performance propellant requires a minimum solids loading
in order to combust properly and this translates into mixtures with high
viscosities that are difficult to 3D print. In addition, it is important to be
able to manufacture realistic propellant formulations into grains that do not
deform and can be precisely functionally graded without the presence of defects
from the printing process. The research presented in this dissertation
identifies the effect of a specific AM process called Vibration Assisted
Printing (VAP) on the combustion of propellant, as well as the development of
binders that enable UV-curing to improve the final resolution of 3D printed structures.
In addition, the combustion dynamics of additively manufactured layered
propellant is studied with computational and experimental methods. The work
presented in this dissertation lays the foundation for progress in the
developing research area of additively manufactured energetic materials. </p>
<p>The appendices of this dissertation
presents some additional data that could also be useful for researchers. A more
detailed description of the methods necessary to support the VAP process,
additional viscosity measurements and micro-CT images of propellant, the
combustion of Al/PVDF filament in windowed propellant at pressure, and microexplosions
of propellant with an Al/Zr additive are all provided in this section. </p>
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Tribological and corrosion properties of Al–12Si produced by selective laser meltingPrashanth, K.G., Debalina, B., Wang, Z., Gostin, P. F., Gebert, A., Calin, M., Kühn, U., Kamara, M., Scudino, S., Eckert, J. 03 June 2020 (has links)
The effect of annealing on the tribological and corrosion properties of Al–12Si samples produced by selective laser melting (SLM) is evaluated via sliding and fretting wear tests and weight loss experiments and compared to the corresponding material processed by conventional casting. Sliding wear shows that the as-prepared SLM material has the least wear rate compared to the cast and heat-treated SLM samples with abrasive wear as the major wear mechanism along with oxidation. Similar trend has also been observed for the fretting wear experiments, where the as-prepared SLM sample displays the minimum wear loss. On the other hand, the acidic corrosion behavior of the as-prepared SLM material as well as of the cast samples is similar and the corrosion rate is accelerated by increasing the heat treatment temperature. This behavior is due to the microstructural changes induced by the heat treatment, where the continuous network of Si characterizing the as-prepared SLM sample transforms to isolated Si particles in the heat-treated SLM specimens. This shows that both the wear and corrosion behaviors are strongly associated with the change in microstructure of the SLM samples due to the heat-treatment process, where the size of the hard Si particles increases, and their density decreases with increasing annealing temperature.
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