Dissertations / Theses on the topic 'Aerospace'
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1
Figueroa, Leonard J. "Aerospace Intrapreneurship: Systems Engineering an Aerospace Front End." Digital Commons at Loyola Marymount University and Loyola Law School, 2017. https://digitalcommons.lmu.edu/etd/394.
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2
Clark, Thomas William. "Aerospace power converter interfaces." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514425.
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3
Jenett, Benjamin (Benjamin Eric). "Digital material aerospace structures." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101837.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-76).
This thesis explores the design, fabrication, and performance of digital materials in aerospace structures in three areas: (1) a morphing wing design that adjusts its form to respond to different behavioral requirements; (2) an automated assembly method for truss column structures; and (3) an analysis of the payload and structural performance requirements of space structure elements made from digital materials. Aerospace structures are among the most difficult to design, engineer, and manufacture. Digital materials are discrete building block parts, reversibly joined, with a discrete set of positions and orientations. Aerospace structures built from digital materials have high performance characteristics that can surpass current technology, while also offering potential for analysis simplification and assembly automation. First, this thesis presents a novel approach for the design, analysis, and manufacturing of composite aerostructures through the use of digital materials. This approach can be used to create morphing wing structures with customizable structural properties, and the simplified composite fabrication strategy results in rapid manufacturing time with future potential for automation. The presented approach combines aircraft structure with morphing technology to accomplish tuned global deformation with a single degree of freedom actuator. Guidelines are proposed to design a digital material morphing wing, a prototype is manufactured and assembled, and preliminary experimental wind tunnel testing is conducted. Seconds, automatic deployment of structures has been a focus of much academic and industrial work on infrastructure applications and robotics in general. This thesis presents a robotic truss assembler designed for space applications - the Space Robot Universal Truss System (SpRoUTS) - that reversibly assembles a truss column from a feedstock of flat-packed components, by folding the sides of each component up and locking onto the assembled structure. The thesis describes the design and implementation of the robot and shows that an assembled truss compares favorably with prior truss deployment systems. Thirds, space structures are limited by launch shroud mass and volume constraints. Digital material space structures can be reversibly assembled on orbit by autonomous relative robots using discrete, incremental parts. This will enable the on-orbit assembly of larger space structures than currently possible. The engineering of these structures, from macro scale to discrete part scale, is presented. Comparison with traditional structural elements is shown and favorable mechanical performance as well as the ability to efficiently transport the material in a medium to heavy launch vehicle. In summary, this thesis contributes the methodology and evaluation of novel applications of digital materials in aerospace structures.
by Benjamin Jenett.
S.M.
4
Ashworth, Geoffrey (Geoffrey John). "Architectural disruption in aerospace." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55202.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 70-71).
Distinctive technology and customer / supplier relationships are currently the primary sources of competitive advantage in the Aerospace industry. Modular Open System Architecture (MOSA) requirements represent a significant disruption to this mode of competition. The United States Department of Defense intends to accelerate the rate of aerospace innovation and inject additional competitiveness into the procurement process through the modularization of its products and effective intellectual property management. This combination of architectural disruption and new customer capabilities has the potential to reduce the industry's opportunity to capture value from innovative technologies or a position as first supplier. Historical examples such as Polaroid and IBM demonstrate the organizational paralysis that often results from disruptions in product architecture. The competitive formula becomes ingrained in the processes, resources, and culture of mature companies and is no longer explicit knowledge, which limits the company's ability to develop the capabilities required to compete in its new environment. Competing in a MOSA environment will require the development of new organizational capabilities such as rapid experimentation, fighting standards wars, and protecting system-level knowledge. Defining the disruptive threat and the foundations of current core competencies will enable firms to develop the organizational capabilities essential for this shift in competitive context.
(cont.) The author will present several historical examples of architectural disruption, a framework for evaluating the disruptive change, and an identification of organizational anchors that may hinder a particular competitor's ability to respond to MOSA. The goal of the thesis is to start a dialogue within an identified incumbent with in hopes of beginning the organizational transformation required to effectively compete in this new era.
by Geoffrey Ashworth.
S.M.
5
Gostic, William J. (William John) 1957. "Aerospace supply chain management." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10000.
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6
Pratt, Roger W. "Control problems in aerospace engineering." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/27604.
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Control Engineering is a wide-ranging discipline which offers opportunities in research to people with diverse backgrounds and interests; from applied mathematicians interested solely in developing new theory right through to pragmatic engineers who are closely involved in a particular application. Additionally, for those involved in the application of control methodologies, there are the bonuses of complementing modelling, analysis and design with experimental validation. For my part, work has centred on the application of existing techniques in new areas. Since the early part of my career were spent in the aircraft industry and the Royal Air Force, it has proved very satisfying to return to this area after some years in 'general' control engineering.
7
Borman, Stephen. "Sensorless drives for aerospace applications." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1447.
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This Engineering Doctorate thesis investigates the different implementations and theories allowing drives to control motors using sensorless techniques that could be used in an aerospace environment. A range of converter topologies and their control will be examined to evaluate the possible techniques that will allow a robust and reliable drive algorithm to be implemented. The focus of the research is around sensorless drives for fuel pump applications, with the potential to replace an existing analogue implementation that is embedded in a fuel pump, contained within the fuel tank. The motor choice (Brushless DC) reflects the requirement for endurance and tight speed control over the life of the aircraft. The study of currently understood sensorless control will allow a critical analysis over the best and most robust sensorless control technique for a controller of this nature, where reliability is a fundamental requirement.
8
Delfa, G. L. a. "Aerospace composite materials in fire." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519566.
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9
Falco, James A. (James Anthony) 1955. "Offsets and the aerospace industry." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10008.
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10
Stimac, Andrew K. (Andrew Kenneth) 1977. "Precision navigation for aerospace applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16676.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Vita.
Includes bibliographical references (p. 162). Includes bibliographical references (p. 162).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Navigation is important in a variety of aerospace applications, and commonly uses a blend of GPS and inertial sensors. In this thesis, a navigation system is designed, developed, and tested. Several alternatives are discussed, but the ultimate design is a loosely-coupled Extended Kalman Filter using rigid body dynamics as the process with a small angle linearization of quaternions. Simulations are run using real flight data. A bench top hardware prototype is tested. Results show good performance and give a variety of insights into the design of navigation systems. Special attention is given to convergence and the validity of linearization.
by Andrew K. Stimac.
S.M.
11
Bílek, Jan. "Aerospace - Futuristický kokpit moderního letounu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2010. http://www.nusl.cz/ntk/nusl-237164.
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This work describes the visualization design of the flight related quantities in a cockpit of a modern light sport aircraft. It focuses on the utilization of the state of the art trends in flight data displays and introduces the innovative implementation of the aircraft's energy state smart clues that reduce pilots' workload. The initial part of the work presents a research into the flight, engine and navigation data presentation on analog instruments, followed by their illustrative depiction in glass cockpits. Within the framework of this thesis, Microsoft Flight Simulator has been used as a source of the flight related data. Final advances in the display design were introduced through the implementation of the synthetic vision system and a visualization of the virtual tunnel in the sky.
12
Brentari, Mirko. "Hybrid Control For Aerospace Systems." Doctoral thesis, Università degli studi di Trento, 2019. https://hdl.handle.net/11572/368808.
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Hybrid dynamical systems are dynamical systems in which continuous and discrete evolutions coexist and interact.
Their twofold nature makes them particularly powerful for both describing and synthesizing complex dynamical behaviors.
In this work we exploit this capability for designing innovative control and estimation algorithms that cope with challenges in aerospace applications.
In particular:
1. we propose different impulsive control strategies for the problem of close-range rendezvous between two spacecrafts in elliptic orbits;
2. we design a robust time-sub-optimal controller for a class of linear systems emerging in aerospace applications where the control input is limited in magnitude;
3. we synthesize an observer to estimate the speed of rotary systems providing angular measurements that evolve on the unit circle.
To this end, we make use of a recent formalism tailored to hybrid dynamical systems for both modeling and proving desirable properties of the proposed algorithms, which are as well confirmed by simulative and experimental validations.
13
Brentari, Mirko. "Hybrid Control For Aerospace Systems." Doctoral thesis, University of Trento, 2019. http://eprints-phd.biblio.unitn.it/3666/2/PhDThesisMirkoBrentari.pdf.
Full textAbstract:
Hybrid dynamical systems are dynamical systems in which continuous and discrete evolutions coexist and interact.
Their twofold nature makes them particularly powerful for both describing and synthesizing complex dynamical behaviors.
In this work we exploit this capability for designing innovative control and estimation algorithms that cope with challenges in aerospace applications.
In particular:
1. we propose different impulsive control strategies for the problem of close-range rendezvous between two spacecrafts in elliptic orbits;
2. we design a robust time-sub-optimal controller for a class of linear systems emerging in aerospace applications where the control input is limited in magnitude;
3. we synthesize an observer to estimate the speed of rotary systems providing angular measurements that evolve on the unit circle.
To this end, we make use of a recent formalism tailored to hybrid dynamical systems for both modeling and proving desirable properties of the proposed algorithms, which are as well confirmed by simulative and experimental validations.
14
Roth, Matthew Adrian. "Vortex lattice methods for aerospace design." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720833.
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15
Landahl, Olof. "Weather visualization for the aerospace industry." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-95274.
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Denna rapport beskriver mitt examensarbete som utfördes på företaget Carmenta AB i Göteborg, hösten 2007. Examensarbetet är den slutgiltiga examinationen för min civilingenjörsutbildning i Medieteknik på Linköpings Universitet. Arbetet gick ut på att undersöka standarder för presentation av väderprognoser för flygtrafik och att implementera lämplig standard i Carmentas kartverktyg SpatialAce. Jag har framställt en studie som går igenom grundläggande teori för flygtrafik och väder, dataformat för lagring och distribution av meteorologisk information samt standarder för visualisering av flygväder. Utvärderingen av studien visar att en så kallad Significant Weather Chart, eller SIGWX, är den främsta visualiseringsstandarden. Denna standard har jag implementerat med hjälp av SpatialAce och programmeringsspråket C#. Dessutom har jag visualiserat vindprognoser enligt de standarder som finns. Detta gjordes också med SpatialAce men i programmeringsspråket C++. Resultatet är en demoapplikation som presenterar dessa prognoser på en karta. Applikationen tillåter även navigering och annan interaktion med kartan.
16
Aouf, Nabil. "Robust control techniques for aerospace vehicles." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38145.
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The research work presented in this thesis deals with flight control problems. Based on robust control techniques such as H infinity control and mu-synthesis, we develop control laws that are efficient in reducing gust loads on flexible aircraft. Uncertainty models for flexible aircraft are proposed and shown to be well adapted for robust control design, while tightly covering unknown but bounded variations of flexible mode parameters. One of the models presented introduces a new complex-rational controller design methodology that takes advantage of the uncertain plant structure and achieves good performance criteria. Other uncertainty models are presented for the first time for the purpose of closed-loop reduction of flexible models. We propose a new model/controller order reduction method for flexible aircraft preserving robust performance in closed loop. Two case studies of complex aircraft are presented with the objective of full flight envelope control. Solutions for scheduled control laws are given to maintain performance objectives along the entire flight envelope. We adapt to our complex aircraft case study known gain scheduling techniques such as observer-form controller scheduling, and we propose new gain scheduling techniques, including a robust performance blending/interpolation design, an optimal multi-switching methodology and a scheduled-partitioned controller.
17
Progoulakis, Losif. "Heated tooling for aerospace composites manufacture." Thesis, University of Plymouth, 2004. http://hdl.handle.net/10026.1/1105.
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The increasingly high capital investment required for large autoclaves, ovens and facilities for the processmg of large composite components creates a number of financial constraints for the development and manufacturing of larger composite aircraft products. This thesis has investigated the use of heated tooling as an alternative to the use of autoclave and oven curing. A design and development methodology for heated tools has been proposed while a number of heated tooling options have been identified and described. Three representative heated tool options using heater mats, electro-conductive textiles and wire heater elements have been evaluated. The curing capability of a prototype heated tool incorporating wire heater elements has been proved by carrying out a number of curing tests on RFI (Resin Fihn Infusion) laminates. The moulded laminates indicate that a 78-83% extent of cure is achieved prior to post-cure. The fibre and void content of cured laminates has also been verified through acid digestion and microscopy, where an acceptable fibre volume fraction (Vf) of 55-57% and a void content of less than 2% have been achieved. The usefulness of ID and 3D thermal Finite Element Analysis for the design and simulation of heated tooling has also been studied. A manufacturing and cost analysis study carried out has identified potential production implications, while the cost effectiveness of heated tooling compared to oven and autoclave processmg has been indicated. Cost reductions are noted in capital investments, operational costs and production set-up costs per part. The work described in this thesis gives valuable information for the implementation of heated tooling as a new processing method for aerospace composite products. The information can prove useful when considermg the processing options of large composite parts such as wing spars, fan cowl doors and wing skins.
18
Butters, Jonathan David. "Terminology recognition in the aerospace domain." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.575750.
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The objects and phenomena within the world around us are frequently shared. Common understandings, intuition, and common sense allow people to communicate ideas and instructions by identifying the semantics of the words used. When we communicate these ideas through text, we rely on strings of characters to carry semantics, and through these, because of common understandings, intuition, and common sense we are often able to gain back the references to the original ideas. As people's capacity to express their ideas through text is unbounded, the task of deciphering original meanings when synonyms and term variations are involved can be challenging, trying to do this task automatically is more so. The body of work within this thesis aims to identify and then overcome the challenges in automatically recognising the terminology used for concepts within the aerospace domain. The main achievements of this thesis include new knowledge about the use of terminology in this safety critical and highly technical domain, knowledge that approaches which are often impractical in open and alternate domains may be applicable due to the aerospace domain's unique nature, and an approach to automatically recognising terminology for the purposes of knowledge management. The approach involves constructing an explicit model of the domain (afforded by its closed nature), and then leveraging it along with exploiting the combinatorial nature of aerospace domain terms in an extraction methodology. Extraction is performed using a novel, hybrid dictionary and machine learning based technique which is shown to perform better than existing dictionary, statistics, and machine learning techniques. This thesis is organised into four parts, the first part provides a survey of the aerospace domain and state of the art methods by which terminology is recognised. The second part documents several investigations into the real-world use of terminology within and across aerospace-based communities in order to provide an understanding on how terminology should be recognised and generate a set of requirements. The third part details the proposed approach and presents a novel, patent-pending methodology to fulfil the requirements. The fourth part concludes this thesis with a summary and by v answering the original research questions, before discussing possible lines of future work.
19
Barker, A. J. "Thin film sensors for aerospace applications." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636037.
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Since Frank Whittle demonstrated the first flight of an aircraft propelled by a turbo-jet engine in the early 1940's the aerospace industry has moved forward at a tremendous pace. Although the principle of operation of such engines has changed little in this time, their performance has soared. During the design and prototype stage of an engine, fluid dynamics models must be proved to ensure flow conditions do not adversely effect the performance. As an aid to this testing, thin film sensors capable of being fabricated directly on vital components have been designed, constructed and tested, for a variety of applications. Three sensors have been concentrated upon: the strain gauge, the hot film anemometer and the pressure sensor. All sensors have been constructed using r.f. plasma enhanced chemical vapour deposition, r.f. magnetron sputtering, photolithography and etching. Thin film strain gauges have been fabricated on special substrates and tested under fatigue conditions. The gauge factor of such devices was approximately 1.8. Flow sensors have been fabricated on flat and cylindrical substrates and tested using an in-house constructed wind tunnel. Thin film anemometers with frequency responses of several hundred kiloHertz have been fabricated, compared to several tens of kiloHertz for the commercial sensor tested. In addition to this, a novel, indirectly heated device has been fabricated, and shows increased sensitivity. Flow sensors have been used to determine the state of the boundary layer under varying flow conditions.
20
Knight, Sylvia Frances. "Natural language processing for aerospace documentation." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621395.
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21
Ebadan, Gracie E. "Laser welding of selected aerospace alloys." Thesis, Loughborough University, 1989. https://dspace.lboro.ac.uk/2134/7114.
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The literature relating to the laser welding of a number of alloys was studied, this revealed gaps in the current state of knowledge. It was found that no indepth parametric or inicrostructural investigations had been carried out into the laser welding of non-ferrous alloys. Although problems associated with the laser welding of aluminium alloys had been identified, there was little in the literature to suggest an indepth study into the effect of surface modifications in enhancing the laser weldability of this material had been carried out. The laser welding of aluminium based metal matrix composites has also yet to be studied in detail. A programme was therefore set up to carry out an indepth investigation into the laser welding of a number of alloys namely; Nimonics C263, and PE11, aluminium 6061, and aluminium 6061 based boron fibre reinforced, and silicon carbide particulate reinforced metal matrix composites. The study was aimed at developing an understanding of the microstructural effects of the laser welding process on the alloys, and assessing the structural integrity of the resultant welds. The effect of laser processing parameters such as laser power, laser beam traverse speed, lens focal length, and the manipulation of these parameters on the welding efficiency and weld area integrity was also investigated. Other tasks within the project included a study on the possibility of using an anodic film to enhance the laser weldability of Al 6061. Finally attempts were made to identify novel phases observed in the weld area of the composite materials. Nimonics C263, and PEll exhibited laser welds free of cracks and porosity. The difference in composition between the two alloys did not result in any significant dissimilarities in their response to the laser welding process. The welds in both alloys exhibited a fine columnar dendritic microstructure, and while carbides were observed in the interdendritic regions of the welds, electron optical analysis did not reveal any y precipitates in this region. It was concluded that for the welding of thin gauge materials above a threshold laser power the resultant welding efficiency shows a greater dependence on laser beam mode, and laser spot size, than on laser power, and beam traverse speed. Aluminium 6061 was not easily welded with a laser in its as received form, and the welds showed some degree of porosity. Anodising was found to improve the welding efficiency in this material. While the presence of an anodic film on the metal surface increased the welding efficiency of the alloy, no relationship was found between the thickness of the anodic film and welding efficiency in the range of film thicknesses investigated in this work. Weld regions were observed to be cellular dendritic in structure, with narrow heat affected zones. No precipitates or low melting point phases could be identified in the weld region. Melt zones were successfully produced in the composite materials, with the main problem encountered being that of porosity adjacent to the weld bead. It was shown that manipulation of the laser welding parameters resulted in a decrease in this porosity. In the weld beads, a number of novel phases were observed. These were identified with the aid of TEM, and SIMS analysis techniques.
22
Kirtley, Aaron L. (Aaron Lloyd) 1977. "Fostering innovation across aerospace supplier networks." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82696.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2002.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
"June 2002." Page 187 blank.
Includes bibliographical references (p. 180-184).
by Aaron L. Kirtley.
S.M.
23
Ferre, Gregoire 1978. "IT management in the aerospace industry." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27014.
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Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2004.Leaf 95 blank.
Includes bibliographical references (leaf 68).
(cont.) payoff IT investments. When the North American Aerospace Industry invests less than any other industry in the high risk investments, its foreign counterpart invests more than any other industry. The second major finding is that the governance mechanisms in place are similar in the two Aerospace Industry segments, contrary to the IT Portfolios. IT decisions are made usually by IT executives or business executives, based on the information provided by Chief level executives and at least one other business group. Finally, the third major finding is that the Aerospace Industry gets above average returns from IT by being good at IT Business Planning, Top Management involvement and User Satisfaction. However, a major effort needs to be placed on improving user satisfaction as it is not always properly managed and hinders returns from IT. The lack of extensive communication also hinders the returns from IT by not guarantying top management involvement and awareness of the IT governance mechanisms.
This thesis originated by a need for the Lean Aerospace Industry to study in the Aerospace Industry what seems to be a troublesome domain for many other industries: Information Technologies (IT). Beforehand, there were two ways to do so: study how aerospace companies implement major systems like Enterprise Resource Planning (ERP) or Product Data Management (PDM). After a few short case studies, it seemed companies were puzzled by the true extent and the pervasiveness of IT. Therefore, we chose to not look at IT "locally" but try to understand the bigger picture. This thesis is largely based on the pioneering work done by Peter Weill and the Center for Information Systems Research of the MIT Sloan School of Management on IT Portfolio and IT governance. It rationalizes IT by setting it as a portfolio, just like financial investments. Balancing the IT portfolio will ensure anticipated alignment with the corporate strategies. However, the elaboration of proper IT governance mechanisms is necessary to ensure value and return from IT. Defining the governance is "specifying the decision rights and accountability framework to encourage desirable behavior on the use of IT". We therefore applied the IT Portfolio and IT governance frameworks defined by Peter Weill to the Aerospace Industry through the analysis of surveys available in Appendix D. We were able to get data from ten different companies spread out across the world. This allowed us to examine several IT profiles, and to make several significant findings, among which three are of major importance and are described below. The first major finding is that the North American IT portfolio is risk-averse, while the aggregated rest of the world is prone to invest heavily in high risk/high
by Gregoire Ferre.
S.M.
24
Roman, Marco Antonio 1971. "Lean aerospace initiative electronic sector study." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/82680.
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Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, 2000.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaf 75).
by Marco Antonio Roman.
S.M.
25
Spendley, Paul R. "Design allowables for composite aerospace structures." Thesis, University of Surrey, 2012. http://epubs.surrey.ac.uk/810072/.
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Recent developments in aircraft design have seen the Airbus A380 and the Boeing Dreamliner employ significant amounts of advanced composite materials. There is some thought however, und the motivation for this current work, that these materials continue to suffer a weight penalty. In this work tests required to generate design allowables which accommodate environmental effects and holes arc performed on Carbon/epoxy quasi-isotropic laminatcs. The test data is treated statistically to provide B-basis allowables for each specimen type and condition. It was seen that the notched specimens (coupons containing a centrally placed through hole) displayed significantly less scatter in strength than unnotched specimens. This is significant when considering the widespread use of deterministic knock-down factors as an alternative route to obtain design allowables which accommodate environmental effects and/or holes. This results in an over-conservative design allowable being employed in subsequent structural design calculations. The possibility for using notched coupons to determine design allowables was explored using the COG (Critical Damage Growth) model. This showed that. given two of the three parameters. the unnotched and notched strength, and fracture toughness the variation in strengths could be reasonable predicted. This leads to a more representative design allowable by maintaining the statistical nature of the B-basis allowable. During the statistical treatment of the test data it was also seen that although current aerospace guidelines recommend a particular distribution model (i.e. the Wcibull distribution) this can also leads to an artificially reduced design allowable. These findings suggest that the use of notched specimens can lead to a reduced development test programme and reduced structural weight.
26
Ameyugo, Gregorio. "Distributed propulsion and future aerospace technologies." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/10029.
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This thesis describes
an
Engineering Doctorate
project
in Distributed Propulsion
carried
out
from 2004 to 2007
at
Cranfield University. Distributed
propulsion
is
a propulsion
system arrangement that consists
in
spreading the engine thrust along the aircraft span.
This
can
be
accomplished
by distributing
a series of
driven fans
or the engines
themselves. The
aim of this project
is to determine the feasibility
of
distributed
propulsion
for
civil aviation
in the medium term (with
small gas turbines) and
long term
(with driven fans) from
a technical and economic perspective.
The
effect of
distributed
propulsion was assessed
by
creating a
long-range
subsonic
airliner
baseline
with conventional technology for the small gas turbines study, and an
equivalent
blended
wing
body baseline for the driven fans
study.
Different distributed
propulsion effects were modelled and
integrated together to produce optimised
baselines
with
different technological parameters.
The feasibility
of small gas turbine distributed
propulsion was
found to be limited by the
excessive
fuel
consumption associated with small gas turbines. Although
advanced
heat
exchanger technology could
improve their performance, the resulting cost advantage
might not
be large
enough to justify the development
costs.
The feasibility
of
distributed driven fans depends on the availability of superconductive
elements, as electrical power transmission seems to be the only promising transmission
method
in the long
run.
If
superconductive elements are applied,
distributed driven fans
could afford
fuel burn
reductions of more than 50%
relative to current technology.
As both distributed
propulsion concepts rely on small propulsive units, their enabling
technologies coincide with those required to develop future
unmanned aerial vehicles.
UAVs therefore represent the most appropriate technological avenue to develop
technologies with
the potential to become distributed
propulsion enablers.
Future
work
should therefore concentrate on
improving
engine performance and cost
for
unmanned
aerial vehicles.
27
RAJYALAKSHMI, P. S., and R. K. RAJANGAM. "FLIGHT INSTRUMENTATION TELEMETRY FOR AEROSPACE APPLICATION." International Foundation for Telemetering, 1986. http://hdl.handle.net/10150/615418.
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International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, NevadaIn Aerospace missions it is often required to have a flexible telemetry system for carrying out flight test on aircraft, in which the bit rate, sampling rate and the number of channels can be programmed. This enables the pilot of the aircraft to reconfigure the telemetry system to suit any particular test missions. An L-Band PCM/FM Telemetry System containing a Stored Programme Multiplexer, 12 bit ADC and other digital interfaces for carrying out the measurements on Speed, Events, etc has been developed as a flight instrumentation telemetry for HAL, India. This paper not only presents complete details of the system, which was qualified to meet MIL-5422 levels but also the performance of the system during actual aircraft missions.
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Farinha, Marques Vitor Manuel. "Lead free solders for aerospace applications." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:85707054-bc46-44f3-b9c6-9fd29358ad25.
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The factors controlling the reliability of Pb-free solders when subject to thermomechanical regimes relevant to the harsh aerospace environment have been studied. Ball grid array (BGAs) typical of microelectronic devices have been manufactured in-house and subjected to isothermal ageing and thermal cycling. The BGAs comprised both Cu and Ni-Au metallizations, Pb-free Sn-Ag-Cu 400 and 600μm solder balls, FR4 and Al2O3 boards, and included circuits to measure resistance changes due to damage in the joints during thermal cycling. Microstructural evolution within the solders balls and complex interfacial reactions were studied in all configurations using various types of electron microscopy. The mechanical properties of the different phases formed within solder joints were studied using nanoindentation at room and elevated temperatures up to 175°C for the first time. Intermetallic compounds (IMCs) were stiff, hard and brittle with very low creep rates, while the softer primary Sn, eutectic regions and Cu metallization readily underwent creep. Two-dimensional finite element analysis (FEA) of nanoindentation was used to understand better the physical meaning of nanoindentation creep data. Reliability experiments comprised both thermal cycling and FEA of BGAs. The difference in coefficient of thermal expansion (CTE) in the BGA materials caused interfacial fatigue damage in the solder joints, which was detected primarily at the solder/metallization interface of the outermost, most strained solder joint. Accumulated creep strain per cycle at this interface was evaluated using 3D FEA of the stress-strain state of the BGA and results calibrated against experimental BGA mean lifetimes using the Coffin-Mason relationship. Nanoindentation combined with FEA has been shown to be a viable route for the rapid assessment of creep performance and lifetime in lead-free solders under aerospace thermal cycles.
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Jönsson, Gustav. "Material selection for an aerospace component." Thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-198494.
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In the world of today there is a drive for lighter and more effective products for various reasons e.g. reduced environmental impact, higher payload, fuel efficiency etc. There is also an expanding development of new materials for a large number of different applications. This makes it more and more difficult for engineers to make good material selections. This has led to the development of a large amount of material selection methods that require more or less effort to select material. An effective way to do this is offered by utilisation of material selection software’s like Granta Design CES Selector [1]. A material selection tool may allow you to investigate and evaluate, unbiased, materials or material designs that meet the product requirements. This can also be used in combination with any selection method to further improve the selection of material. The objective within this work is to propose a strategy for implementing results from material selection tools, e.g. Granta Design, into current set based design optimisation procedures at GKN. Through this new materials and their impact on an existing design may be explored in a rational way. This is then presented through materials selection in a case study. The case is to select material for the cone at the rear of a jet engine and come up with three design proposals. Two methods are used to achive this, Ashby’s method utilized in Granta Design for finding suitable materials, and the QFD-method [] for ranking the proposed materials. Granta design uses material property charts where material properties are presented against each other i.e. Young’s modulus versus density and then a material index is inserted in the graph to see how well different material perform against the index. The index varies depending on function of the structure i.e. a beam, on the constraints i.e. stiffness specified and on the goal i.e. minimize weight and this index is to be maximized for maximum performance. The materials are ranked against all possible material indices for the specific structure in this case the cone. Specific requirements are also possible to insert into Granta design i.e. the materials must handle at least 400°C and all materials not fulfilling the requirements or the material indices are removed. The remaining materials are presented in a list where there material performance index (MPI), how well they fulfil the material index, is presented. To rank these, since different materials have varying performance compared to different indices the QFD-method [3] is used. The QFD-method is based on goals set up by the designer and then the material indices are weighed against these goals in a systematic way. These are then used to rank the materials MPI. The materials are then studied to find out availability, environmental issues and produceability to make the final decision. Granta design can also be used to create new materials by combining different materials i.e. sandwich. This is used to fill gaps in the materials property charts and find materials performing better than monolithic materials. Three design proposals were retrieved and studied using FEM-software ANSYS. The first using a monolithic shell in Ti-6Al-4V titanium alloy with a weight of 51.157 kg, the second a sandwich with face material of Ti-6Al-4V and core material of Ti-6Al-4V honeycomb. This has a weight of 36.3 kg. The third design is a stiffened shell of Ti-6Al-4V with stiffeners of Stainless steel, PH 13-8Mo, H1150. Here the concept of shape factors where different materials can be shape to different slenderness and thus higher effectivity before buckling is utilized and therefore the stainless steel performs better than the titanium.
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Schäfer, Lukas Matthias. "Design of reliable aerospace system architecture." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31391.
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Reliability and redundancy of safety-critical network systems is a paramount issue in system engineering. Be it in evaluating existing network systems or solving optimization problems for designing network systems, it is important to consider reliability and redundancy. This dissertation is in collaboration with AIRBUS Group, France, and they are very interest in the optimal design of safety-critical aircraft architecture systems which have to consider reliability and redundancy. To address the problem of optimally designing such systems, we chose to focus on one specific aircraft architecture system the door management system. It checks if all doors are properly closed and the cabin has the correct pressure. It is a safety-critical system since it is part of the pressurization system of an aircraft. To optimally design the DMS while considering reliability, a suitable reliability evaluation algorithm is necessary. In this dissertation, we begin by proposing a suitable reliability evaluation algorithm for a type of non series-parallel network system which includes the DMS and which can be used in an optimization model. The reliability evaluation algorithm is based on a simplification of the probability principle of inclusion-exclusion formula for intersections of unions. The simplification exploits the presence of many repeated events and has many fewer terms, which significantly reduces the number of operations needed. We compare its computational efficiency against the sum of disjoint products method KDH88 for a simple artificial example and for the DMS. Afterwards, we introduce the first MILP model for the DMS with k-redundancy. As the model is too difficult to be solved efficiently by standard MILP solvers, we discuss the issues of solving the model with general solving methods such as branch-and-bound and branch-and-price. We introduce specialized branching rules and new heuristics to solve the DMS problem with k-redundancy more efficiently and show results of computational tests which compare the specialized solving algorithms with general solving algorithms for example instances of the DMS problem. Lastly, we discuss the problems of considering reliability in MI(N)LP models for the DMS and how the new reliability evaluation algorithm can be used. In this discussion, we give different MI(N)LP models for the DMS problem with redundancy and reliability. Moreover, we propose a new heuristic for the DMS problem with redundancy and reliability. It is based on branch-and-bound, the Dantzig-Wolfe decomposition and on the new reliability evaluation algorithm. We show results of computational tests of the new heuristic for example instances of the DMS problem and discuss its validity.
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Yeremenko, Roman, and Valeri Badakh. "Public access data in aerospace industry." Thesis, ORT Publishing, 2019. http://er.nau.edu.ua:8080/handle/NAU/40228.
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In industries like an aerospace engineering a large amount of researches is funded by the corporations, which grant special access to the specific documentation and data to affiliated scientists and may provide internship to affiliated universities students. The downside of above-mentioned model is that it might complicate the researches that require general statistical design and/or performance data from the wide range of products (such as aircrafts or helicopters), thus complicating predictions of trends in the field, which could be detrimental to conceptual advancement of aerospace engineering as a whole, as well as to providing the cutting-edge industry awareness to students, teachers and researchers alike.
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Hanuska, Alexander Robert Jr. "Thermal Characterization of Complex Aerospace Structures." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36617.
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Predicting the performance of complex structures exposed to harsh
thermal environments is a crucial issue in many of today's aerospace
and space designs. To predict the thermal stresses a structure might
be exposed to, the thermal properties of the independent materials
used in the design of the structure need to be known. Therefore, a
noninvasive estimation procedure involving Genetic Algorithms was
developed to determine the various thermal properties needed to
adequately model the Outer Wing Subcomponent (OWS), a structure located at the trailing edge of the High Speed Civil Transport's (HSCT) wing tip.
Due to the nature of the nonlinear least-squares estimation method
used in this study, both theoretical and experimental temperature
histories were required. Several one-dimensional and two-dimensional finite element models of
the OWS were developed to compute the transient theoretical
temperature histories. The experimental data were obtained from
optimized experiments that were run at various surrounding
temperature settings to investigate the temperature dependence of the
estimated properties. An experimental optimization was performed to
provide the most accurate estimates and reduce the confidence
intervals.
The simultaneous estimation of eight thermal properties, including the
volumetric heat capacities and out-of-plane thermal conductivities of
the facesheets, the honeycomb, the skins, and the torque tubes, was
successfully completed with the one-dimensional model and the results used to
evaluate the remaining in-plane thermal conductivities of the
facesheets, the honeycomb, the skins, and the torque tubes with the
two-dimensional model. Although experimental optimization did not eliminate all
correlation between the parameters, the minimization procedure based
on the Genetic Algorithm performed extremely well, despite the high
degree of correlation and low sensitivity of many of the parameters.Master of Science
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Hamad, Baran, and Markus Englund. "Improved Release Mechanisms for Aerospace Applications." Thesis, Uppsala universitet, Tillämpad mekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448399.
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Hold down release mechanisms (HDRMs) are used for tightly attaching segments of bodies together when it is desired to release them rapidly at some point. When transporting sensitive payloads on launch vehicles, the challenge arises of releasing the fastened segments of the spacecraft without risking damage to the costly equipment. Non-explosive HDRMs are favourable from a safety perspective as there is a lower risk of producing potentially destructive shock-waves throughout the structure. One variant of a non-explosive HDRM uses a so called 'split spool initiator'. This initiator can only be used once in the actuator mechanism and to reuse the HDRM the initiator must be replaced. The purpose of this thesis is to design an improved split spool initiator which can be reusable while conserving the functionality aspects of the existing design. To achieve this, different ideas were considered and ultimately a solution using shape memory alloys (SMAs) was explored. A prototype was constructed to demonstrate the functionality of the design and simulations are done to determine the forces acting on different parts of the mechanism.Hold down release-mekanismer (HDRM) används för att säkert kunna fästa samman delar av strukturer för att sedan kunna lossa dessa vid rätt tillfälle. När det transporteras känslig last på exempelvis rymdfarkoster uppkommer utmaningen att göra så på ett sätt som inte riskerar att skada den ofta dyra utrustningen. Det finns en mängd olika HDRM, dessa kan delas upp i två typer som är icke explosiva release-mekanismer och pyrotekniska release-mekanismer. Icke explosiva release-mekanismer har en fördel över pyrotekniska som är att de inte producerar potentiellt destruktiva chock-vågor som sprids genom strukturen. En typ av icke-explosiva release-mekanismer är den så kallade split spool-initieraren. Denna kan endast användas en gång när fästelementet är aktiverat och för att kunna använda fästelementet igen måste hela initieraren bytas ut. Syftet med denna studie har varit att att designa en förbättrad split spool-initierare som är återanvändbar, medan funktionaliteten hos den ursprungliga designen är bevarad. För att åstadkomma detta övervägdes olika idéer och slutligen valdes en lösning som använder minnesmetaller eller Shape memory alloys på engelska (SMA). En prototyp konstruerades för att demonstrera funktionaliteten hos designen. Simuleringar gjordes även för att bestämma krafter som agerade på split spool-strukturen och för att få en överblick över spänningsfördelningen genom initieraren.
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Saotome, Tsuyoshi. "Transparent polymer nanocomposites for aerospace applications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1970611211&sid=54&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Riva, Sephira. "Scandium metal processing for aerospace application." Thesis, Swansea University, 2018. https://cronfa.swan.ac.uk/Record/cronfa39867.
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The use of scandium has been conventionally restricted to minor additions in alloys for structural applications. The term ‘scandium effect’ came thus to indicate the properties improvements caused by the precipitation of scandium intermetallics in the matrix. The development of High-Entropy Alloys (HEA, multi-principal component alloys combining compositional complexity with simple crystal structures) opened the door for the development of new systems, and therefore for new applications for lightweight metals such as scandium. This work is a thorough investigation of the potential of scandium-based in- termetallics in the growing field of HEAs. The synthesis and characterisation of multi-principal component alloys contain- ing scandium as active alloying element illustrate the compound-forming ability of this element. The high mixing entropy of the studied systems (comprising alloys of scandium with first raw metals or with hcp-structured elements) cannot efficiently inhibit the precipitation of stable intermetallic compounds. Among them, of in- terest is the so-called W -phase, so-far only reported for Al-basedCu-containing commercial alloys. Small scandium additions to Al2CoCrFeNi, Al0.5CoCrCuFeNi and AlCoCr- Cu0.5FeNi cause the segregation of a secondary phase along grain boundaries. This hexagonal Laves phase, formed by scandium in combination with Al, Co, Cr, Cu, Fe and Ni, does not disrupt the HEA matrix and is extremely stable. Moreover, it deeply affects microstructure and mechanical properties – for ex-ample, by enhancing the HEA stability with the postponement of a T-dependent phase exsolution by roughly 150 °C. Furthermore, a synergistic effect in the main phase stabilisation takes place when the Sc-doped sample is pressed at 9.5 GPa: no transition occurs and the intermetallic dissolves in the matrix. Preliminary investigations performed by spark-plasma sintering of different additives (among which Sc2O3, used as a source of scandium metal) in combination with the Al CoCrFeNi alloy led to the discovery of a promising nanodiamond HEA composite.
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Frauenberger, Douglas H. "Lean transformation in aerospace assembly operations." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39728.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; in conjunction with the Leaders for Manufacturing Program at MIT, 2007.Includes bibliographical references (p. 81-82).
For the past two decades, virtually all manufacturing companies in the United States have adopted or are in the process of adopting lean manufacturing. Globalization has resulted in the increased availability of reliable, low cost sources putting greater pressures on traditional US manufacturing companies to reduce costs. The need to successfully transform to lean has only grown in importance in this new operating environment, resulting in renewed focus on such initiatives in the United States. This thesis discusses various approaches to lean manufacturing with reference to specific examples from both academia and industry. In particular, lean transformation efforts in Mitchell Engine Company's* Final Assembly Plant will be provided as a case study. Focus on the JP-3525 fan case assembly cell provides specific examples on how shop floor improvements, assembly cell redesign, and flow can improve process cycle time and decrease variability. The direct result of this work has been a 15% decrease in cycle time and a 100% decrease in variability in the JP-3525 fan case assembly cell. Finally, the role front-line supervisors play in change initiatives will be introduced, discussing the position from both management and labor perspectives. Based on past research, recommendations will be made on how to improve cell leader effectiveness, recognizing these changes require systemic change within the organization.
by Douglas H. Frauenberger.
M.B.A.
S.M.
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McQuarrie, Allan J. (Allan John) 1963. "Fire fighting in aerospace product development : a study of project capacity and resource planning in an aerospace enterprise." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29535.
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Thesis (S.M.)--Massachusetts Institute of Technology, System Design & Management Program, 2003.Includes bibliographical references.
It is broadly recognized in the aerospace industry, as well as many others, that organizations which effectively execute development projects to meet desired cost, schedule, and performance targets for their customers produce higher levels of customer satisfaction and also a significant source of competitive advantage. Continually meeting the needs of the customer through effective project execution allows a company to become a preferred supplier favored in source selection for follow-on contracts and new development projects necessary for business growth. This research effort examines one aerospace company, which has multiple, diverse development projects on-going at any one time across several business units. The motivation for this thesis is to explore the product/system development capacity of the enterprise by analyzing the historical program performance of major projects, understanding the level of problem projects or fire fighting within the project pipeline, and the perceived causes of poor project performance. In addition, system dynamics models are developed to analyze the dynamics associated with project planning and resource planning strategies for both multi-project and single project scenarios. This analysis provides insight into the potential for project pipeline "tipping" and the effects of various project management and resource planning strategies in an aerospace product/system development context. Such analysis is believed to provide greater insight and opportunity to improve the product/system development performance for the enterprise.
by Allan J. McQuarrie, Jr.
S.M.
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Liaghati, Amir, Nick Chang, Mahsa Liaghati, and John Blumer. "PREDICTIVE TELEMETRY MODELS FOR AEROSPACE FLIGHT MISSIONS." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/627017.
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Designing an efficient telemetry system is one of the most challenging tasks in the aerospace industry due to the limited telemetry bandwidth and the restricted radio frequency spectrum allocation. In a traditional telemetry system design, a large percentage of the allotted bandwidth is consumed by the overhead information to follow various standards and protocols which results in inefficiency of output data. A dynamic simulation model is created by using the Matlab/Simulink to analyze the telemetry system performance, and it is also used to predict the overall downlink data, including sensor instrumentation, flight critical information, video, and the Consultative Committee for Space Data System (CCSDS) overhead over the mission event timeline.
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Strubel, Vincent. "Particle entrapment in EHD contacts - Aerospace applications." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI098/document.
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Une lubrification suffisante est essentielle au bon fonctionnement des mécanismes et/ou composants comme par exemple les paliers à roulement. Par contre, les lubrifiants contiennent souvent des débris d’usure ou des polluants extérieurs. Ces particules micrométriques peuvent pénétrer des contacts d’épaisseur inférieure au micromètre induisant des empruntes ou indents pouvant conduire à des endommagements irréversibles pour les surfaces en contact. L’objet de ce travail est l’étude du piégeage de polluants solides à l’aide de particules sphériques d’acier, d’un point de vue théorique, numérique et expérimental. Dans un premier temps, une étude phénoménologique a été proposée à l’aide d’une nouvelle méthode expérimentale basée sur la technique PIV combinée à un tribomètre bille/disque. Les trajectoires des polluants à l’entrée du contact ont pu ainsi être identifiées. En parallèle, un modèle numérique d’écoulement du lubrifiant a été développé pour permettre l’évaluation des conditions menant au piégeage ou non de particules. Finalement, des expériences sur une machine bi-disques en conditions de lubrification polluée contrôlée ont permis de valider les tendances observées pour le piégeage. Une première série de résultats a montré que le piégeage de contaminants est fortement dépendant du profil de vitesse du lubrifiant. Un taux de piégeage très hétérogène a été observé sur des contacts avec une ellipticité transverse à l’écoulement variable. De manière surprenante, malgré une augmentation de la largeur de contact, une forte diminution du nombre de particules piégées a été observée dans des contacts elliptiques. Il a été démontré que cette diminution pouvait être imputée à la présence d’importants reflux de lubrifiant dans les contacts elliptiques larges. L’étude de contacts hybrides, nitrure de silicium–acier, a montré une bonne résistance à l’indentation du nitrure de silicium. Il est à noter que les contacts hybrides présentent des niveaux de piégeage similaire à un contact tout acierContact lubrication is essential in a wide range of mechanical systems like rolling element bearings (REBs). A minimum quantity of clean lubricant all along the bearing life is necessary but difficult to ensure. In fact, lubricants contain inevitably wear debris or external particles, like dust. Carried by the lubricant in the vicinity of elastohydrodynamic (EHD) contacts, particles can be entrapped with disastrous consequences for contacting surfaces. Entrapment of micrometric particles in submicrometric contacting gaps means irreversible damages for the surfaces. Damages weaken the surfaces and reduce significantly the REBs lifetime. The goal of this work is to analyze the critical particle entrainments in the contact inlet. Entrapment of steel spherical particles was investigated from the numerical and experimental point of view. Firstly, the phenomenology of entrapment was explored with a new experimental method based on Particle Image Velocimetry (PIV) technique installed on a tribometer. It enabled the evaluation of velocity profiles in the contact inlet and the tracking of particles within EHD contacts. Secondly, a numerical modelling of the inlet flow for EHD contacts, including the particle tracking, was developed. Finally, tests on a twin-disc machine with a controlled level of well-defined contamination were conducted to validate previous conclusions. A first set of results showed that particle entrapment is highly dependent on the lubricant velocity profile. Depending on contact geometry, from point to wide elliptical contacts, different entrapment probability were revealed. Surprisingly, increasing contact width with wide elliptical contacts leads to a drop of entrapped particles. It was demonstrated that this phenomenon is due to backflows occurring upstream from these contacts. Introducing a hybrid pair of contacting materials (silicon nitride–steel), dents on the surfaces due to entrapped particles were explored. It has been confirmed that silicon nitride surface offers a real ability to resist to indentation. It was also noticed that the entrapment probability for silicon nitride–steel contacts is equivalent to a steel–steel one
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White, Caleb, and caleb white@rmit edu au. "Health Monitoring of Bonded Composite Aerospace Structures." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090602.142122.
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Airframe assemblers have long recognised that for a new aircraft to be successful it must use less fuel, have lower maintenance requirements, and be more affordable. One common tactic is the use of innovative materials, such as advanced composites. Composite materials are suited to structural connection by adhesive bonding, which minimises the need for inefficient mechanical fastening. The aim of this PhD project was to investigate the application of existing, yet immature Structural Health Monitoring (SHM) techniques to adhesively bonded composite aerospace structures. The PhD study focused on two emerging SHM technologies - frequency response and comparative vacuum monitoring (CVM). This project aimed to provide missing critical information for each technique. This included determining sensitivity to damage, repeatability of results, and operating limitations for the frequency response method. Study of the CVM technique aimed to address effectiveness of damage detection, manufacture of sensor cavities, and the influence of sensor integration on mechanical performance of bonded structures. Experimental research work is presented examining the potential of frequency response techniques for the detection of debonding in composite-to-composite external patch repairs. Natural frequencies were found to decrease over a discrete frequency range as the debond size increased; confirming that such features could be used to both detect and characterise damage. The effectiveness of the frequency response technique was then confirmed for composite patch and scarf repair specimens for free-free and fixed-fixed boundary conditions. Finally, the viability of the frequency response technique was assessed for a scarf repair of a real aircraft component, where it was found that structural damping limited the maximum useable frequency. The feasibility of CVM technique for the inspection of co-cured stiffener-skin aircraft structures was explored. The creation of sensor cavities with tapered mandrels was found to significantly alter the microstructure of the stiffener, including crimping and waviness of fibres and resin-rich zones between plies. Representative stiffened-skin structure with two sensor cavity configurations (parallel and perpendicular to the stiffener direction) was tested to failure in tension and compression. While tensile failure strength was significantly reduced for both configurations (up to 25%), no appreciable differences in compression properties were found. Two potential sensor cavity configurations were investigated for the extension of the CVM technique to pre-cured and co-bonded scarf repair schemes. The creation of radial and circumferential CVM sensor cavities was found to significantly alter the microstructure of the adhesive bond-line and the architecture of the repair material in the case of the co-bonded repair. These alterations changed the failure mode and reduced the tensile failure strength of the repair. A fibre straightening mechanism responsible for progressive failure (specific to co-bonded repairs with circumferential cavities) was identified, and subsequently supported with acoustic emission testing and numerical analysis. While fatigue performance was generally reduced by the presence of CVM cavities, the circumferential cavities appeared to retard crack progression, reducing sensitivity to the accumulation of fatigue damage. These outcomes have brought forward the implementation of SHM in bonded composite structures, which has great potential to improve the operating efficiency of next generation aircraft.
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Letovsky, Robert. "Public policy and the Quebec aerospace sector." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ47721.pdf.
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Levedahl, Blaine Alexander. "Decentralized Autonomous Control of Aerospace Vehicle Formations." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-03062003-104749/.
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Two approaches for the autonomous control of aerospace vehicle formations are developed. The development of the approaches relies on fundamental work in the areas of distributed control; specifically modal, robust, optimal, and decentralized control. The algorithms are shown to satisfy five separation principles that simplify design and enable the algorithms to be implemented reliably. The autonomous controllers uniformly dampen the modes of the formation (global control) using a decentralized approach and a nearest-neighbor approach. A numerical example illustrates robust formation changes from 9-vehicle (3 x 3) grids to V-type formations.
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Marvasti, Mazda Alim. "Applications of fractal geometry in aerospace engineering." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/12079.
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Lazim, Duraid. "Springback in draw-bending on aerospace alloys." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79244.
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The springback phenomenon was studied by a series of draw-bend tests. These tests were done by varying the blankholding pressure with different lubrication conditions, and with different transverse anisotropy directions. The purpose is to find the forming loads, the thickness changes and the springback angles. It has been found that the springback angle after unloading depends on the amount of blankholding pressure, the material properties, and the tool geometry. Increasing the blankholding pressure almost eliminates the springback if the tensile stress caused by the blankholding pressure reaches the yield in the material. To compliment the experiments, a theoretical model has been developed by calculating the tensile strain developed from applying the blankholding pressure. This strain then was considered in finding the total bending moment.
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Ma, Weitao. "Cost modelling for manufacturing of aerospace composites." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6279.
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The application of composites has been increasing dramatically in aerospace structures recently, for example, composites have contributed over 50 percent of the structure mass of large transport airplanes Boeing 787 and Airbus 350XWB. However, the further usage has been restricted because of the high material and manufacturing costs. Hence, it is essential to utilize cost estimation tools for accurate cost estimation in the early design stages, and then efficient decisions and design optimizations could be made to reduce the cost of composite products. This research project aims to develop a cost model for aerospace carbon fibre reinforced plastic (CFRP) composites, which will help designers and cost engineers with the cost estimation for composites manufacturing in the early development stages. The main objectives of the research are to: (i) recognise the standard manufacturing stages and activities of CFRP components; (ii) identify the cost drivers of composites manufacturing; (iii) identify the cost estimation relationships; (iv) develop a cost model that can assist designers and engineers with manufacturing cost estimation for CFRP components; (v) validate the developed cost model through case studies and expert judgements. The process of model development was carried out through four main steps: firstly, conducting an integrated understanding of cost modelling for composites manufacturing; secondly, collecting data for cost modelling from industry and existing literature and databases; thirdly, developing the cost model with several function modules and databases; and finally, taking a validation of the developed model. The developed cost model consists of several modules: material selection, process planning, cost estimation, cost reporting and a user friendly interface. Moreover, the selection and planning modules are combined with databases including material and process. The developed model enables the user to estimate the manufacturing cost and process time of CFRP composites, and it can also help designers realize the impact of design changes on the manufacturing cost. The process planning can efficiently help estimators with manufacturing process understanding and accurate time estimation. Quality control activities are time consuming and investment sensitive in composites manufacturing.
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Ashry, Mahmoud Mohamed. "Control of multivariable aerospace and industrial systems." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504785.
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This thesis presents theoretical and practical issues of local optimal control, which is one of the advanced control methods. It can be counted as an optimal modelbased multivariable control technique. The main contributions of this work can be summarized as follows. A comparative robustness study of local optimal controller with other conventional controllers is performed for gas turbine engine as a multivariable system. As the original local optimal control is incapable to deal with non-minimum phase systems, a modified local optimal control is proposed to deal with non-minimum phase systems as well as minimum phase systems. The local optimal controller performance is investigated for reduced order models. Because of its effectiveness, genetic algorithm is used with certain predefined controller structures as an alternative method to estimate the controller parameters without obtaining the model parameters. A new tuning technique of digital PID controller is introduced for both multivariable and single-input single-output systems based on the relations deduced with the local optimal controller. As such, the PID controller is turned into model-based controller. As tlie PIO and the local optimal controller are model based multivariable controllers, their parameters can be tuned online based on online identification techniques. The recursive lease squares algorithm is used as an online . closed loop identification technique to achieve such online tuning of those controller parameters. Local optimal controller is generalized to deal with non-linear systems as a non-linear controller. Most of the above techniques are tested on a laboratory-based test rig.
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Jaffery, Mujtaba Hussain. "Precision landing and testing of aerospace vehicles." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551147.
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Planetary precision landing in non-cooperative sites has been a major challenge. An indoor novel planetary precision landing facility known as Surrey Precision Landing Facility (SPLF) has been developed to bridge the gap between software simulations and outdoor expensive UA V based planetary precision landing testbeds. The 3D motion capture system provides real-time accurate navigation data by removing the uncertainty in the position, and thus allows the flexibility to test the planetary terminal descent based Guidance and Control algorithms on quadrotors safely, rapidly, repeatedly with very low operating cost. Quadrotors can follow the trajectory of a planetary lander during its terminal descent. Model Predictive Control (MPC) incorporates input/output constraints in the calculation of the control law and thus can be used for the planetary terminal descent scenarios. Feasibility and computation time have been a key hindrance in practical validation of MPC for quadrotor control. Therefore, a novel single stage linear MPC algorithm in a state-space framework has been developed to improve feasibility and computation time over Optimal MPC (OMPC), Laguerre OMPC (LOMPC) and Steady-State (SS) OMPC (SSOMPC) by linking reference governor, Closed-Loop Paradigm, Steady-State Target Optimization and Laguerre function techniques. The novel SSLOMPC algorithm is simulated to test its performance on a simple two state model, and then has been implemented in simulation and practically validated at SPLF on a quadrotor for the set-point tracking scenarios. Disturbance rejection and offset free tracking is achieved via a Kalman filter. . Simulated and practical implementations of PID, LQR and MPC control laws on a quadrotor helicopter for the Mars terminal descent phase has been performed at SPLF, where SSOMPC/SSLOMPC successfully demonstrates the ability to respect the control input and output constraints. The conclusion is that the use of Steady-State OMPC with Laguerre functions improves feasibility and computation time. MPC can be used as a practical candidate controller for planetary precision landing scenarios. The tracking errors for PID, LQR and MPC control laws were less than 10 cm in the practical tests.
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Tuppen, S. J. "Resistance bonding of titanium based aerospace alloys." Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639270.
Full textAbstract:
The current research was commissioned to assess the feasibility of fabricating bonds between a range of commercially available titanium based aerospace alloys, using a low-cost direct resistance heating technique. A novel methodology has been devised and implemented which utilises a Gleeble facility to produce controlled resistance bonds. The optimisation of bonding parameters required to produce high quality joints is discussed i.e. the effects of surface treatment, pressure, time, temperature and environment. Optimised bond conditions have been defined for joining Ti 6/4 to itself and TNB (gamma titanium aluminide) to itself, negating the requirement for specialised surface treatments. In addition, a collaborative venture with Birmingham University was established to incorporate novel surface treatments using an electrical discharge machining procedure. In this respect, Ti 6/4 and TNB bonding couples utilising integral copper recast surface braze layers have been suitably optimised. Finally, the bonding of the dissimilar alloy combination Ti 6/4 to Ni-Ti (shape memory alloy) has been attempted using butt welding (with and without a Cu-Ni interlayer) and eutectic bonding procedures. However, bonding of this material combination proved difficult and this specific pairing may be incompatible using the present technique. Metallographic sections, chemical composition and micro-hardness traverses across all bond lines are presented as evidence of the form and integrity of the resulting joints. The mechanical performance of the bonds was assessed under monotonic tensile loading conditions.
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Wechsler, Andrew Philip. "Improving fault tolerant drives for aerospace applications." Thesis, University of Newcastle Upon Tyne, 2013. http://hdl.handle.net/10443/1841.
Full textAbstract:
The aerospace industry is moving towards the more electric aeroplane where traditional hydraulic systems are being replaced with electrical systems. Electrical technology offers some strong advantages compared to hydraulic technology including; cost, efficiency, power on demand and relative ease of maintenance. As with most new technologies, a major disadvantage is its limited reliability history. A lot of research in the aerospace field therefore focuses on improving fault tolerant electrical systems. Work done in this thesis builds on an existing fault tolerant drive, developed by Newcastle University and Goodrich Actuation Systems as part of the ELGEAR (Electrical Landing Gear) project. The purpose of this work is to continue improving the drive’s fault tolerant features; especially in areas where the drive is most vulnerable. The first part of this thesis focuses on improving the overall system reliability by monitoring the health of the dc-link capacitors in the fault tolerant drive. The implemented estimation technique makes use of voltage and current sensors which are already in place for protection and control purposes. The novel aspect of the proposed technique relates to monitoring capacitors in real time whilst the motor is operational. No external interferences, such as injected signals or special operation of the drive, are required. The condition monitoring system is independent of torque and speed, and hence independent of a variation in load. The work was validated using analytical methods, simulation, low voltage experimentation and high voltage implementation on the ELGEAR drive. The second part of this thesis focuses on single shorted turn faults, in fault tolerant permanent magnet (PM) motors. Despite the motor being able to withstand a wide range of faults, the single shorted turn fault remains a difficult fault to detect and handle. The problem arises from the magnets on the spinning rotor that cannot be ‘turned off’ at will. This thesis investigates the severity of the faulted current in a shorted turn and how it varies depending on the turn’s location in the stator slot. The severity of the fault is studied using 2D finite element analysis and practical implementation on the ELGEAR rig. Finally, recommendations are proposed for improving the ELGEAR motor for future fault tolerant designs.
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Kudesia, Sean Swarup. "Precision Nd:YAG laser drilling of aerospace materials." Thesis, Heriot-Watt University, 2003. http://hdl.handle.net/10399/387.
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