To see the other types of publications on this topic, follow the link: COMPOSITE ROTOR.
Dissertations / Theses on the topic 'COMPOSITE ROTOR'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'COMPOSITE ROTOR.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Soykasap, Omer. "Aeroelastic optimization of a composite tilt rotor." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11823.
Full text
2
Ozbay, Serkan. "Extension-Twist Coupling Optimization in Composite Rotor Blades." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10422.
Full textAbstract:
For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different.
Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass.
A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept provides for tailoring of the structure without any additional weight penalty on the system.
3
Turnock, Wingyan Wong. "Impact response of composite helicopter rotor blades." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422188.
Full text
4
Pawar, Prashant M. "Structural Health Monitoring Of Composite Helicopter Rotor Blades." Thesis, Indian Institute of Science, 2006. https://etd.iisc.ac.in/handle/2005/273.
Full textAbstract:
Helicopter rotor system operates in a highly dynamic and unsteady aerodynamic environment leading to severe vibratory loads on the rotor system. Repeated exposure to these severe loading conditions can induce damage in the composite rotor blade which may lead to a catastrophic failure. Therefore, an interest in the structural health monitoring (SHM) of the composite rotor blades has grown markedly in recent years. Two important issues are addressed in this thesis; (1) structural modeling and aeroelastic analysis of the damaged rotor blade and (2) development of a model based rotor health monitoring system. The effect of matrix cracking, the first failure mode in composites, is studied in detail for a circular section beam, box-beam and two-cell airfoil section beam. Later, the effects of further progressive damages such as debonding/delamination and fiber breakage are considered for a two-cell airfoil section beam representing a stiff-inplane helicopter rotor blade. It is found that the stiffness decreases rapidly in the initial phase of matrix cracking but becomes almost constant later as matrix crack saturation is reached. Due to matrix cracking, the bending and torsion stiffness losses at the point of matrix crack saturation are about 6-12 percent and about 25-30 percent, respectively. Due to debonding/delamination, the bending and torsion stiffness losses are about 6-8 percent and about 40-45 percent after matrix crack saturation, respectively. The stiffness loss due to fiber breakage is very rapid and leads to the final failure of the blade. An aeroelastic analysis is performed for the damaged composite rotor in forward flight and the numerically simulated results are used to develop an online health monitoring system. For fault detection, the variations in rotating frequencies, tip bending and torsion response, blade root loads and strains along the blade due to damage are investigated. It is found that peak-to-peak values of blade response and loads provide a good global damage indicator and result in considerable data reduction. Also, the shear strain is a useful indicator to predict local damage. The structural health monitoring system is developed using the physics based models to detect and locate damage from simulated noisy rotor system data. A genetic fuzzy system (GFS) developed for solving the inverse problem of detecting damage from noise contaminated measurements by hybridizing the best features of fuzzy logic and genetic algorithms. Using the changes in structural measurements between the damaged and undamaged blade, a fuzzy system is generated and the rule-base and membership functions optimized by genetic algorithm. The GFS is demonstrated using frequency and mode shape based measurements for various beam type structures such as uniform cantilever beam, tapered beam and non-rotating helicopter blade. The GFS is further demonstrated for predicting the internal state of the composite structures using an example of a composite hollow circular beam with matrix cracking damage mode. Finally, the GFS is applied for online SHM of a rotor in forward flight. It is found that the GFS shows excellent robustness with noisy data, missing measurements and degrades gradually in the presence of faulty sensors/measurements. Furthermore, the GFS can be developed in an automated manner resulting in an optimal solution to the inverse problem of SHM. Finally, the stiffness degradation of the composite rotor blade is correlated to the life consumption of the rotor blade and issues related to damage prognosis are addressed.
5
Pawar, Prashant M. "Structural Health Monitoring Of Composite Helicopter Rotor Blades." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/273.
Full textAbstract:
Helicopter rotor system operates in a highly dynamic and unsteady aerodynamic environment leading to severe vibratory loads on the rotor system. Repeated exposure to these severe loading conditions can induce damage in the composite rotor blade which may lead to a catastrophic failure. Therefore, an interest in the structural health monitoring (SHM) of the composite rotor blades has grown markedly in recent years. Two important issues are addressed in this thesis; (1) structural modeling and aeroelastic analysis of the damaged rotor blade and (2) development of a model based rotor health monitoring system. The effect of matrix cracking, the first failure mode in composites, is studied in detail for a circular section beam, box-beam and two-cell airfoil section beam. Later, the effects of further progressive damages such as debonding/delamination and fiber breakage are considered for a two-cell airfoil section beam representing a stiff-inplane helicopter rotor blade. It is found that the stiffness decreases rapidly in the initial phase of matrix cracking but becomes almost constant later as matrix crack saturation is reached. Due to matrix cracking, the bending and torsion stiffness losses at the point of matrix crack saturation are about 6-12 percent and about 25-30 percent, respectively. Due to debonding/delamination, the bending and torsion stiffness losses are about 6-8 percent and about 40-45 percent after matrix crack saturation, respectively. The stiffness loss due to fiber breakage is very rapid and leads to the final failure of the blade. An aeroelastic analysis is performed for the damaged composite rotor in forward flight and the numerically simulated results are used to develop an online health monitoring system. For fault detection, the variations in rotating frequencies, tip bending and torsion response, blade root loads and strains along the blade due to damage are investigated. It is found that peak-to-peak values of blade response and loads provide a good global damage indicator and result in considerable data reduction. Also, the shear strain is a useful indicator to predict local damage. The structural health monitoring system is developed using the physics based models to detect and locate damage from simulated noisy rotor system data. A genetic fuzzy system (GFS) developed for solving the inverse problem of detecting damage from noise contaminated measurements by hybridizing the best features of fuzzy logic and genetic algorithms. Using the changes in structural measurements between the damaged and undamaged blade, a fuzzy system is generated and the rule-base and membership functions optimized by genetic algorithm. The GFS is demonstrated using frequency and mode shape based measurements for various beam type structures such as uniform cantilever beam, tapered beam and non-rotating helicopter blade. The GFS is further demonstrated for predicting the internal state of the composite structures using an example of a composite hollow circular beam with matrix cracking damage mode. Finally, the GFS is applied for online SHM of a rotor in forward flight. It is found that the GFS shows excellent robustness with noisy data, missing measurements and degrades gradually in the presence of faulty sensors/measurements. Furthermore, the GFS can be developed in an automated manner resulting in an optimal solution to the inverse problem of SHM. Finally, the stiffness degradation of the composite rotor blade is correlated to the life consumption of the rotor blade and issues related to damage prognosis are addressed.
6
Atilgan, Ali Rana. "Towards a unified analysis methodology for composite rotor blades." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/15403.
Full text
7
Ku, Jieun. "A Hybrid Optimization Scheme for Helicopters with Composite Rotor Blades." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16268.
Full textAbstract:
Rotorcraft optimization is a challenging problem due to its conflicting requirements among many disciplines and highly coupled design variables affecting the overall design. Also, the design
process for a composite rotor blade is often ambiguous because of its design space. Furthermore, analytical tools do not produce
acceptable results compared with flight test when it comes to aerodynamics and aeroelasticity unless realistic models are used, which leads to excessive computer time per iteration.
To comply these requirements, computationally efficient yet realistic tools for rotorcraft analysis, such as VABS and DYMORE were used as analysis tools. These tools decompose a three-dimensional problem into a two-dimensional cross-sectional and a one-dimensional beam analysis. Also, to eliminate the human interaction between iterations, a previously VABS-ANSYS macro was
modified and automated. The automated tool shortened the computer time needed to generate the VABS input file for each analysis from
hours to seconds. MATLAB was used as the wrapper tool to integrate VABS, DYMORE and the VABS-ANSYS macro into the methodology. This methodology uses Genetic Algorithm and gradient-based methods as
optimization schemes. The baseline model is the rotor system of generic Georgia Tech Helicopter (GTH), which is a three-bladed, soft-in-plane, bearingless rotor system. The resulting methodology is a two-level optimization, global and local. Previous studies showed that when stiffnesses are used as design variables in
optimization, these values act as if they are independent and produce design requirements that cannot be achieved by local-level optimization. To force design variables at the global level to stay within the feasible design space of the local level, a surrogate model was adapted into the methodology. For the surrogate model,
different ``design of experiments" (DOE) methods were tested to find the most computationally efficient DOE method. The response surface
method (RSM) and Kriging were tested for the optimization problem.
The results show that using the surrogate model speeds up the optimization process and the Kriging model shows superior performance over RSM models. As a result, the global-level optimizer
produces requirements that the local optimizer can achieve.
8
Macedo, Moura Geraldo A. "An approach for design and analysis of composite rotor blades." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25698.
Full text
9
SHARMA, ANUJ. "DEVELOPMENT, CHARACTERIZATION AND DYNAMIC ANALYSIS OF METAL MATRIX COMPOSITE ROTOR." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18893.
Full textAbstract:
Industrial development is one of the pioneer enablers of the economic and social prosperity
of any nation. High efficiency, low cost and reliable system are the most critical factors
that are focussed by industries. New developments in this direction are observed in the past
few decades. Researchers thrive for new inventions and technologies by which high-quality
output can be attained with effective and robust systems. Materials play an essential role
in achieving high efficiency by providing an outcome-based response to any process. With
the advent of composite materials, industries have started focusing on using lighter weight
materials with the same mechanical properties. Metal matrix composites have the edge
over the parent metals for rotor applications as it has a higher specific modulus and specific
modulus is the critical material factor for vibration responses. Aluminium /alumina MMCs
have shown prominent growth in the composite material market because of their
compatibility with the rotor systems. Several types of research are available for the
development of aluminium based metal matrix composites for industrial applications.
The main focus of this research is to propose a method of development of metal
matrix composite for specific rotary applications. This work focuses on the development,
characterization and dynamic analysis of the metal matrix rotor. The rotors are developed
through a cost-effective, flexible, and readily available method called the stir casting
process.
The physical properties of the composites depend primarily on the homogeneity
and the fraction of reinforcement in the matrix. The uniformity and the concentration have
been enhanced by optimizing process parameters in various researches. However, these
vii
researches are based on the qualitative analysis (visual observation) of the microstructure
of composites. These qualitative methods do not assist in providing numerical and
objective-oriented results. Therefore, these methods lack a objective judgment that is
crucial for comparing the dispersion of reinforcements consistently. Therefore, quantitative
measurement of dispersion is essential for optimizing the process parameters in order to
attain better results.
There are several techniques for the quantitative measurement of particle dispersion
in the matrix. The mean free path has been calculated by dividing micrograph images into
multiple grid lines and was utilized for quantifying particle dispersions. The quantitative
distribution index and area fraction may be beneficial in optimizing the process parameters
and providing more authentic and reliable results than the qualitative analysis. There are
various methods used for parametric optimization having multivariant parameters. Box-
Behnken designs (BBD) are rotatable or nearly rotatable second-order designs based on
three-level incomplete factorial designs. BBD is one of the main types of response surface
design, the other being central composite design. The BBD design requires a smaller
number of runs as compared to the central composite design. The Box-Behnken design
operates within the range of parameters and does not generate experimentation points
beyond the range of parameters like the central composite design. BBD is suitable for
designs where the range of operations are constrained by manufacturing conditions. In this
work, a novel technique has been adopted where newly developed quantitatively assessed
responses are used for process optimization instead of conventional qualitative analysis
and thus, it provides a profound methodology for optimization of process parameters.
viii
A novel characterization approach has been adopted in this work, which determines
the effect of reinforcements on the dynamic properties and residual stress of the Al
6061/Al2O3 shafts. Long and slender shafts were fabricated through a stir casting process.
Grain structure has been obtained through optical microscopy, and morphological
evaluation of the composites was performed through Scanning Electron Microscopy
(SEM). In addition to that, an X-ray diffraction pattern (XRD) were analyzed, and residual
stress was calculated by X-ray residual stress measurement system μ-X360 Ver. 2. 3. 0. 1.
Tensile strength and microhardness were also determined in this analysis for various
compositions of the composite material.
For composite materials, the system response changes abruptly with a change in the
properties of the material. Therefore, attaining significant knowledge about the effect of
material composition on material properties is crucial. The researchers are looking for new
computational methods which can predict these alterations so that the effort in
experimental testing can be reduced. In this direction, this paper presents a robust and novel
methodology of validating the estimation of the composite's effective properties through a
multi-scale approach by a set of standardized experimentation. These effective properties
are estimated through the mean-field homogenization technique, whose parameters are
driven from the image analysis of Scanning Electron Microscopy (SEM) images. The
predicted results are validated with the results obtained by the experimentation as per
ASTM E1876 standard.
This research work has adopted a novel approach of providing a dedicated
methodology for determining the calibrated internal damping factor for bond graph
dynamic analysis, which has been used in various literature for transient and stable
ix
responses. The investigation has been performed on long and slender shafts of the metal
matrix composites. An insight into the change in dynamic response with the difference in
the composition of composite shafts is provided in this work.
Many valuable insights and findings were obtained in this work related to the
development and response of different compositions of metal matrix composite shafts. The
optimization of the stir casting parameters using a quantitative distribution index and area
fraction resulted in uniformly distributed composite shafts. The mechanical properties such
as tensile strength, microhardness, specific modulus increased with the addition of
reinforcement in the composite up to a particular limit. Above that limit, the agglomeration
and porosity become prominent factors and further depletes the properties of a composite.
The natural frequency of the composite shaft increased, and the amplitude of vibration was
reduced for the composites with a high volume fraction of reinforcements. The values of
Young's modulus of different compositions determined through computation were
congruent with the experimental results. The dynamic response was simulated using bond
graph analysis, and it was observed that the amplitude of orbits was also reduced for the
composites with a high volume fraction of reinforcements.
10
Bailey, Brent. "Investigation of a composite hingeless helicopter rotor blade with integral actuators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0024/MQ52385.pdf.
Full text
11
Wickramasinghe, Viresh K. (Viresh Kanchana) 1971. "Characterization of active fiber composite actuators for helicopter rotor blade applications." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/82200.
Full text
12
Bailey, Brent Carleton University Dissertation Engineering Mechanical and Aerospace. "Investigation of a composite hingeless helicopter rotor blade with integral actuators." Ottawa, 2000.
Find full text
13
Toh, Ee Liang Raymond. "A computational and experimental investigation into the strains within a composite rotor." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/8192.
Full text
14
Visweswaraiah, Swaroop. "Structural design and multi-objective optimization of an advanced composite rotor blade." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97179.
Full textAbstract:
Advanced composite materials provide a wide range of design freedom by virtue of their anisotropy. For the structural design and optimization of an advanced composite rotor blade, computationally efficient analytical models that can simulate the behaviour of the blade are necessary. A reliable and computationally efficient in-house cross-sectional analysis code has been developed for applications in the preliminary analysis and structural optimization of composite rotor blades. Parametric studies emphasizing the influence of the changes made to the internal structure of the blade are presented to illustrate the variation of the elastic stiffnesses and the coupling stiffness terms as a function of the internal geometry changes. Box-beam and D-spars that are the idealizations of a composite airfoil structure are considered in this work. The variation of the elastic stiffnesses for the actual blade structure with NACA0015 (symmetrical airfoil) and NACA23015 (cambered airfoil) profiles have been accomplished. The internal geometry changes considered include: the web inclination angle of the spar and the web distance from the leading edge. A discussion on the effect of these changes on the actual and idealized structures has been reported. In addition, multi-objective optimization of the cross-sectional design of a helicopter rotor blade with NACA0015 profile has been performed using the min-max approach. The optimization problem has been formulated as target vector optimization while considering the internal geometry variables of the blade. Particle swarm optimization, a multi-agent direct search algorithm, has been selected for the optimization due to its efficacy in dealing with composite optimization problems. A comparison of the optimization results with/without the inclusion of the internal geometry variables has been reported to highlight the role that the internal geometry variables play in the structural design of composite rotor blades.Keywords: Advanced composite rotor blades, Elastic tailoring, Multi-objective optimization, Target vector optimization, Particle swarm optimization.Grâce à leurs propriétés anisotropiques, les matériaux composites avancés présentent une grande liberté en termes de conception et design. Afin de concevoir et optimiser une pale principale en matériaux composites avancés, des modèles analytiques pouvant simuler le comportement de la pale sont nécessaires. Un code mathématique fiable and efficace, en terme de puissance de calcul, a été développé pour faire des analyses préliminaires d'optimisation structurelle de pales principales en composite. Des études paramétriques, démontrant l'influence des changements faits à la structure interne de la pale, sont présentées pour illustrer la variation des modules de rigidité et des termes de couplage de rigidité en fonction de la géométrie interne de la pale.Un caisson et un longeron, qui sont une idéalisation d'un profil aérodynamique en composite, ont été considéré dans ce travail. La variation des modules élastiques de rigidité pour des structures de pales symétriques NACA0015 et cambrées NACA23015 a été déterminée. Les changements de géométrie interne considérés inclus : l'angle d'inclinaison de l'âme du longeron et la distance entre l'âme et le bord d'attaque. Une discussion sur l'effet de ces changements sur les structures réelles et idéalisées est présentée.De plus, une optimisation à objectifs multiples du design de la section transversale d'une pale d'hélicoptère avec un profil NACA0015 a été accomplie avec une approche min-max. Le problème d'optimisation a été formulé en tant qu'une optimisation à vecteur cible tout en considérant les variables géométriques internes de la pale. Une optimisation à essaim de particules, un algorithme de recherche direct à cibles multiples, a été sélectionnée pour l'optimisation à cause de son efficacité à gérer les problèmes d'optimisation avec les composites. Une comparaison des résultats d'optimisation incluant ou non les variables de géométrie internes a été reportée pour souligner le rôle que celles-ci jouent dans la conception structurelle des pales en composite.
15
Minguet, Pierre Jacques. "Static and dynamic behavior of composite helicopter rotor blades under large deflections." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/40146.
Full text
16
Li, Leihong. "Structural design of composite rotor blades with consideration of manufacturability, durability, and manufacturing uncertainties." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24757.
Full textAbstract:
Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Hodges, Dewey H.; Committee Member: Bauchau, Olivier A.; Committee Member: Johnson, Ellis; Committee Member: Makeev, Andrew; Committee Member: Volovoi, Vitali V.
17
Lv, Peng. "Performance aérodynamique et structurelle du rotor flexible pour micro-drones." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0058/document.
Full textAbstract:
Les essais en environnement libre et en soufflerie ont été effectués pour étudier la performance propulsive et la déformation de pales de référence et de pales souples. La poussée et le couple ont été évalués par deux méthodes: une mesure directe par balance et une estimation indirecte par bilan de quantité de mouvement, les deux méthodes ayant leurs avantages et limitations respectifs. La méthode indirecte s’est construite sur l’acquisition de champs de vitesse obtenus par PIV et s’appuie sur une estimation de la pression par mise en œuvre de l’équation de Poisson. En vol stationnaire, les pales flexibles ne peuvent pas aider à l’amélioration du rendement en mode rotor (FM), à chargement faible, puisque la distribution de vrillage est sans doute assez éloignée de l’optimal de vol stationnaire. En vol avancé, le rendement propulsif des pales flexibles est la plupart du temps plus élevé que l’hélice rigide de référence en raison de la torsion bénéfique généré en rotation. Dans le cas des pales flexibles, la vitesse axiale se trouve être inférieure au cas rigide, à même station aval; ceci correspondant à la la déformation de vrillage négatif. Pour les deux pales, la différence de poussée entre celle déduite du champ PIV test 2et celle obtenue avec la balance est plus grande que la différence entre les valeurs déduites du champ PIV test 1 et de la mesure directe. La technique de mesure laser pour les déplacements(LDS) a été utilisée pour mesurer la déformation stationnaire des pales lors de leur rotation. Par analyse du nuage de points mesurés par la LDS, la flexion et la torsion de la lame en rotation ont été identifiées à l’aide des régressions multiplesThe wind tunnel tests were conducted to explore the performance difference caused by the potential twist deformation between baseline blades and flexible blades. The balance was built in SaBre wind tunnel for measuring the thrust and torque of blades. The BEMT predictions of blades with varied twist were also performed in hover and forward flight, respectively. In hover,flexible blades cannot help in improving the FM at light disk loading since the twist generated on flexible blades is probably beyond the ideal hover twist. In forward flight, the propulsive efficiency η of flexible blades is mostly higher than baseline blades due to the beneficial twist generated in rotation. A Particle Image Velocimetry (PIV) approach of loads determination was developed based on control volume method to obtain thrust and torque of small-scale proprotor,especially for off-optimum conditions. The pressure Poisson equation was implemented for the pressure estimation based on the PIV velocity data. The axial velocity of flexible blades is found to be lower than baseline blades on the same station at downstream. This corresponds to the lower inflow ratio distribution along flexible blade, which results from the negative twist deformation. For both baseline blades and flexible blades, the thrust differences between PIV test 2 and balance are larger when compared to the differences between PIV test 1 based on nearfield and balance. The Laser Displacement Sensor (LDS) technique was employed for measuring the stationary deformation of rotating flexible blades. By obtaining the LDS point cloud, the bending and torsion of the rotating blade were identified using the multiple regressions
18
Karaolis, Nicos M. "The design of fibre reinforced composite blades for passive and active wind turbine rotor aerodynamic control." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235661.
Full text
19
Lasseigne, Alexis. "Optimization of variable-thickness composite structures. Application to a CROR blade." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEM006/document.
Full textAbstract:
Cette thèse aborde la problématique de la conception optimale de structures composites stratifiées d’épaisseur variable. Les variables d’empilement définissent un problème d’optimisation combinatoire et des espaces de décisions de grande taille et potentiellement multimodaux. Les algorithmes d’optimisation stochastiques permettent de traiter ce type de problème et de tirer profit des performances et de l’anisotropie des plis composites pour l’allègement des structures composites stratifiées. Le but de cette étude est double : (i) développer un algorithme d’optimisation dédié aux composites stratifiés d’épaisseur variable et (ii) estimer le potentiel des composites stratifiés pour la maîtrise des performances aérodynamiques d’une pale de CROR composite.Dans la première partie de cette thèse, un algorithme évolutionnaire est spécialisé pour l’optimisation de tables de drapage et la gestion d’un ensemble de règles de conception représentatif des pratiques de l’industrie. Pour se faire, un encodage spécifique des solutions est proposé et des opérateurs de variations spécialisés sont développés.Dans la deuxième partie, l’algorithme est enrichi d’une technique de guidage basée sur l’exploitation d’un espace auxiliaire afin d'accroître son efficacité et d’intégrer davantage de connaissances des composites dans la résolution du problème.Finalement, la méthode est appliquée pour la conception d’une pale de CROR composite à l’échelle de la maquette de soufflerie. Au préalable, des processus itératifs de mise à froid et mise à chaud de la pale sont mis en place afin d’estimer la forme de la pale au repos et l’état de contraintes dans la pale en fonctionnementThis thesis deals with the optimal design of variable-thickness laminated composite structures. The stacking variables define a combinatorial optimization problem and large decision spaces which are potentially multimodal. Stochastic optimization algorithms allow solving this type of problem and allow taking advantage from the performance and the anisotropic nature of unidirectional composite plies to lighten laminated composite structures.The purpose of this study is twofold: (i) developing an optimization algorithm dedicated to variable-thickness laminated composites and (ii) assessing the potential of laminated composites in influencing the aerodynamic performances of a composite CROR blade.Firstly, an evolutionary algorithm is specialized in order to optimize layup tables and handle a set of design guidelines which is representative of industrial practices. In this purpose, a specific encoding of the solutions is suggested and specialized variation operators are developed.Secondly, the algorithm is enriched with a guiding technique based on the exploitation of an auxiliary space in order to improve its efficiency and to include further composites-related knowledge for the resolution of the problem.Finally, the method is applied for the design of a reduced-scale composite CROR blade intended for wind-tunnel testing. Beforehand, iterative processes are implemented to estimate the shape of the non-operating blade and the stress state within the operating blade
20
Fu, Ping Rong Kimberly. "Study and development of novel composite materials for the application of car brake rotor." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2321.
Full textAbstract:
From experimental study of properties including density, tensile strength, Young’s modulus, fracture toughness for both aluminium alloy reinforced with silicon carbide and aluminium alloy reinforced with alumina representing metal matrix composites, and measurements of compressive strength for the above composites and alumina and aluminium titanate based ceramics as functionally graded materials, together with estimated thermal conductivity and specific heat capacity, show promising results for the use of these materials for car brake rotor.
21
Kim, Taehyoun 1959. "Nonlinear large amplitude structural and aeroelastic behavior of composite rotor blades at large static deflection." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/43251.
Full text
22
Lalonde, Stéphanie. "Investigation into the static and fatigue behaviour of a helicopter main rotor yoke made of composite materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0030/MQ64232.pdf.
Full text
23
Chakravarty, Uttam Kumar. "Section builder: a finite element tool for analysis and design of composite." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22640.
Full textAbstract:
Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2008.Committee Chair: Bauchau, Olivier; Committee Member: Craig, James; Committee Member: Hodges, Dewey; Committee Member: Mahfuz, Hassan; Committee Member: Volovoi, Vitali.
24
Rajagopal, Anurag. "Advancements in rotor blade cross-sectional analysis using the variational-asymptotic method." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51877.
Full textAbstract:
Rotor (helicopter/wind turbine) blades are typically slender structures that can be modeled as beams. Beam modeling, however, involves a substantial mathematical formulation that ultimately helps save computational costs. A beam theory for rotor blades must account for (i) initial twist and/or curvature, (ii) inclusion of composite materials, (iii) large displacements and rotations; and be capable of offering significant computational savings compared to a non-linear 3D FEA (Finite Element Analysis). The mathematical foundation of the current effort is the Variational Asymptotic Method (VAM), which is used to rigorously reduce the 3D problem into a 1D or beam problem, i.e., perform a cross-sectional analysis, without any ad hoc assumptions regarding the deformation. Since its inception, the VAM based cross-sectional analysis problem has been in a constant state of flux to expand its horizons and increase its potency; and this is precisely the target at which the objectives of this work are aimed. The problems addressed are the stress-strain-displacement recovery for spanwise non-uniform beams, analytical verification studies for the initial curvature effect, higher fidelity stress-strain-displacement recovery, oblique cross-sectional analysis, modeling of thin-walled beams considering the interaction of small parameters and the analysis of plates of variable thickness. The following are the chief conclusions that can be drawn from this work:
1. In accurately determining the stress, strain and displacement of a spanwise non-uniform beam, an analysis which accounts for the tilting of the normal and the subsequent modification of the stress-traction boundary conditions is required.
2. Asymptotic expansion of the metric tensor of the undeformed state and its powers are needed to capture the stiffnesses of curved beams in tune with elasticity theory. Further improvements in the stiffness matrix can be achieved by a partial transformation to the Generalized Timoshenko theory.
3. For the planar deformation of curved laminated strip-beams, closed-form analytical expressions can be generated for the stiffness matrix and recovery; further certain beam stiffnesses can be extracted not only by a direct 3D to 1D dimensional reduction, but a sequential dimensional reduction, the intermediate being a plate theory.
4. Evaluation of the second-order warping allows for a higher fidelity extraction of stress, strain and displacement with negligible additional computational costs.
5. The definition of a cross section has been expanded to include surfaces which need not be perpendicular to the reference line.
6. Analysis of thin-walled rotor blade segments using asymptotic methods should consider a small parameter associated with the wall thickness; further the analysis procedure can be initiated from a laminated shell theory instead of 3D.
7. Structural analysis of plates of variable thickness involves an 8×8 plate stiffness matrix and 3D recovery which explicitly depend on the parameters describing the thickness, in contrast to the simplistic and erroneous approach of replacing the thickness by its variation.
25
Miersch, Sören, Ralph Schubert, Thomas Schuhmann, Uwe Schuffenhauer, Markus Buddenbohm, Markus Beyreuther, Jeannette Kuhn, Mathias Lindner, Bernd Cebulski, and Jakob Jung. "Ceramic-like Composite Systems for Winding Insulation of Electrical Machines." IEEE, 2020. https://htw-dresden.qucosa.de/id/qucosa%3A74384.
Full textAbstract:
Insulating sheets, impregnants and encapsulation materials commonly used for winding insulation offer low thermal conductivities. This leads to an increased heating of the winding of electrical machines and to the existence of hotspots. The electromagnetical utilization of the machine has to be reduced with respect to the allowed maximum winding temperature. In this paper, the development and experimental investigation of novel polysiloxane composites with ceramic fillers are presented. The materials are tested by means of impregnated and encapsulated samples of a round-wire winding as well as the main insulation of electrical steel sheets and laminated cores. Numerical models are implemented for determining the equivalent thermal conductivity of the winding compound comprising the enameled wire and the impregnant. Based on the example of a permanent-magnet synchronous machine with outer-rotor in modular construction, the potential for increasing the electromagnetical utilization is shown.
26
Sarker, Pratik. "Dynamic Response of a Hingeless Helicopter Rotor Blade at Hovering and Forward Flights." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2545.
Full textAbstract:
The helicopter possesses the unrivaled capacity for vertical takeoff and landing which has made the helicopter suitable for numerous tasks such as carrying passengers and equipment, providing air medical services, firefighting, and other military and civil tasks. The nature of the aerodynamic environment surrounding the helicopter gives rise to a significant amount of vibration to its whole body. Among different sources of vibrations, the main rotor blade is the major contributor. The dynamic characteristics of the hingeless rotor consisting of elastic blades are of particular interest because of the strongly coupled equations of motion. The elastic rotor blades are subjected to coupled flapping, lead-lag, and torsional (triply coupled) deflections. Once these deflections exceed the maximum allowable level, the structural integrity of the rotor blade is affected leading to the ultimate failure. The maximum deflection that a blade can undergo for a specific operating condition needs to be estimated. Therefore, in this study, the triply coupled free and forced response of the Bo 105 hingeless, composite helicopter rotor blade is investigated at hovering and forward flights. At first, a model of the composite cross-section of the rotor blade is proposed for which a semi-analytical procedure is developed to estimate the sectional properties. These properties are used in the mathematical model of the free vibration of the rotor blade having the proposed cross-section to solve for the natural frequencies and the mode shapes. The aerodynamic loadings from the strip theory are used to estimate the time-varying forced response of the rotor blade for hovering and forward flights. The large flapping and inflow angles are introduced in the mathematical model of the forward flight and the corresponding nonlinear mathematical model requires a numerical solution technique. Therefore, a generalization of the method of lines is performed to develop a robust numerical solution in terms of time-varying deflections and velocities. The effect of the unsteady aerodynamics at the forward flight is included in the mathematical model to estimate the corresponding dynamic response. Both the analytical and the numerical models are validated by finite element results and the convergence study for the free vibration is performed.
27
Moisy, Amélie. "Imprégnation capillaire anisotherme et polymérisation d'une résine thermodurcissable dans un bobinage composite de rotor électrique : Caractérisation expérimentale, modélisation et simulation du couplage multiphysique." Electronic Thesis or Diss., Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0052.
Full textAbstract:
Dans le cadre de l'électrification du parc automobile, Renault assemble ses propres moteurs électriques : le rotor est principalement composé d'un noyau en acier sur lequel sont bobinés des fils de cuivre isolés. Le bobinage est ensuite immergé dans un bain de résine liquide thermodurcissable assurant la performance et la durabilité du moteur. L'imprégnation, faite à température contrôlée pour faciliter l'écoulement et la polymérisation, n'implique pas de pressurisation. Cela suggère que la capillarité et la gravité jouent un rôle significatif. L'objectif global est d'évaluer laqualité de l'imprégnation. Cela requiert de caractériser, modéliser et simuler un procédé multi-matériaux et multi-physiques dans lequel transfert thermique, cinétique de polymérisation et écoulement capillaire sont fortement couplés. Les matériaux sont caractérisés (cinétique de polymérisation, viscosité, propriétés thermiques et de surface) pour modéliser leur comportement temporel et thermique. Ensuite, pour un cas unidirectionnel idéal, un montage expérimental original de suivi de l'imprégnation par prise en masse à température contrôlée est conçu et développé. Des essais de 20°C à 120°C permettent de mieux comprendre les phénomènes et l'influence des paramètres. Un modèle analytique simplifié est optimisé pour correspondre aux expériences. Pour compléter, une simulation anisotherme 2D couplée est réalisée sur un domaine homogénéisé, fournissant les gradients de polymérisation et thermiques et leur impact sur la dynamique d'écoulement. Enfin, l'analyse est montée en échelle sur une bobine de type rotor. Un autre montage original basé sur les diélectriques est développé pour mesurer le flux de résine. La simulation de l’imprégnation de la bobine est présentéeIn the mobility electrification context, the Renault Group assembles its own electric engines: the rotor is mainly composed of a steel core wound by insulated copper wires. The winding is immersed into a thermosetting resin bath ensuring the performance and durability of the motor. The impregnation occurs under controlled temperature to facilitate the flow and the polymerization. This process does not involve any pressurization. This suggests that capillary and gravity forces play a significant role. The global objective is to evaluate the impregnation quality. It requires characterizing, modeling and simulating a multi-materials andmulti-physics process in which heat transfer, polymerization kinetics and capillary-driven resin flow are strongly coupled. The materials are characterized (polymerization kinetics, viscosity, thermal and surface properties) to model their temporal and thermal behavior. Then, for an ideal unidirectional coil, an original temperaturecontrolled experimental resin weight intakefollow-up setup is designed and developed. Tests from 20°C to 120°C enable a deeper understanding of the phenomena andparameters’ influence. A simplified analytical model is optimized to match the experimental results. To complete, a coupled 2D anisothermal simulation is performed on a homogenized domain, providing the polymerization and thermal gradients and their impact on fluid dynamics. Finally, the analysis is up-scaled for a rotor-like coil. Another original dielectric-based setup is developed to measure the resin flow experimentally. The simulation of the coil’s impregnation is provided
28
Taufik, Atik. "Contribution au développement d'un outil de conception des poutres composites : application aux pales d'hélicoptères." Toulouse, ENSAE, 1996. http://www.theses.fr/1996ESAE0017.
Full textAbstract:
Ce travail porte sur l'analyse de poutres composites à section complexe. Dans une première partie, l'étude est limitée aux matériaux anisotropes dont un axe d'orthotropie est parallèle à l'axe longitudinal de la poutre. La méthode utilisée est basée sur le principe des travaux virtuels. Le code réalisé à partir de cette théorie permet de calculer toutes les grandeurs caractéristiques d'une section droite. L'étude est complétée par une analyse des problèmes relatifs à la torsion à gauchissement gêné et au couplage torsion-effort normal. La méthode est étendue aux poutres dont l'orientation des axes d'orthotropie des matériaux est quelconque. Ceci est réalisé en utilisant une formumation unifiée du vecteur déplacement et en appliquant le principe des travaux virtuels. Le code de calcul basé sur cette théorie a été développé et il permet de déterminer tous les termes de couplage. Dans la dernière partie, une méthode et un programme sont réalisés pour optimiser la forme d'une section droite pour une masse minimale et avec des contraintes imposées. Ceci est rendu possible grâce au mailleur paramétré développé.
29
Pavlík, Ondřej. "Návrh kompozitní objímky rotoru vysokootáčkového rotačního stroje." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382567.
Full textAbstract:
The diploma thesis focuses on manufacturing carbon fiber and epoxy composite material using filament winding method. Material properties of manufactured composite are ap-proximated using analytical and numerical homogenization models. Calculated material properties are applied to design and evaluate reserve factor of retaining sleeve for high speed brushless permanent magnet synchronous motor. Margin of safety of designed rotor is evaluated using composite failure criteria. Test stand for both static and dynamic testing is designed, static test stand is manufactured and assembled. Static strength test is carried out.
30
Skladanek, Yan. "Formulation d’un élément fini de poutre pour la dynamique des pales d’hélicoptère de géométrie complexe." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0122.
Full textAbstract:
L'optimisation des rotors d'hélicoptère, tant en termes de forme, de structure interne, ou de performance aérodynamique conduit à explorer de nouveaux types de design pour les pales. L'emploi massif de matériaux composites, le recours à des formes courbes et non plus simplement droites ou encore l'ajustement du vrillage aérodynamique font partie des pistes explorées. Ces nouveaux concepts de pales font apparaitre des comportements élastiques complexes où la torsion, la flexion et l'allongement axial viennent se coupler entre eux. L'étude de ces couplages est réalisée dans le repère tournant afin de pouvoir y intégrer tous les effets inhérents à la rotation des pales. Un élément fini de poutre droite non-linéaire et haute précision est formulé dans ce mémoire afin de répondre aux besoins de modélisation tant pour la prédiction des déformations quasi-statiques sous charge aérodynamique et centrifuge que pour la réalisation d'études dynamiques et de stabilité sur les pales. Le modèle a pour but d'être implémenté dans un code de calcul global de simulation d'hélicoptère et se doit donc de proposer un compromis acceptable entre la précision, la robustesse et le temps de calcul. La validation du modèle proposé s'appuie sur des études analytiques, numériques et expérimentales. La grande précision de l'élément fini proposé est démontrée sur des pales de dernière génération. Il est maintenant attendu que le couplage de ce modèle élastique avec les modèles aérodynamiques les plus avancés permette d'améliorer sensiblement la précision des outils de simulation, en particulier lors de l'étude de phénomènes instables dont la maitrise est indispensable au vol de l'hélicoptèreStructural, shape and performances optimization in helicopter rotor leads to design composite blades initially curved and twisted. This design yields a highly coupled behavior between torsion, longitudinal and bending motions of blades. Besides, dynamic studies of blades have to be performed in the rotational frame, so that all rotatory effects could be siezed by the modeling. A highly accurate non-linear straight beam finite element is proposed to predict the static deformation under aerodynamic and centrifugal loads and achieve dynamic and stability analysis. This elastic model is to be implemented in a comprehensive rotorcraft analysis code, which means accuracy, reliability and calculation time compromise. Model validation is based on analytical, numerical and experimental investigations. The developed model reveals to be very accurate for new blade design including important twist angle and initially curved shape. It is expected to improve prediction quality for full helicopter simulation tools, undergoing strong coupling with advanced aerodynamic model
31
Janse, van Rensburg Petrus J. "Energy storage in composite flywheel rotors." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17864.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: As the push continues for increased use of renewables on the electricity grid, the problem of energy storage is becoming more urgent than ever. Flywheels with wound, composite rotors represent an efficient and environmentally friendly option for energy storage. They have already been applied successfully for voltage control on electrical rail networks and for bridging power in backup UPS systems, but lately they have also proven useful for grid-scale frequency regulation. For flywheels to be deployed on a wider scale, the high cost associated with the technology will have to be addressed. An important driver of cost is the density at which energy can be stored. Currently, flywheel designs do not consistently achieve high energy density, and this study investigates the reasons for this. A critical analysis is made of the design methodologies that have been proposed in the available literature, and some improvements are suggested. Most notably it is shown that significant improvements in energy density may be possible if the design optimization problem is formulated carefully. In addition, the problem of material selection is discussed, because material properties have a significant influence on energy density. Some guidance is given for flywheel designers on how to choose an optimal set of materials without invoking undue computational effort. It is hoped that these suggestions may be carried forward as a topic of further research.
AFRIKAANSE OPSOMMING: Namate die aanvraag vir hernubare energie op die elektrisiteit netwerk vergroot, word die probleem van energie berging van kardinale belang. Vliegwiele met silindriese rotors van samegestelde materiale bied ’n effektiewe en omgewingsvriendelike opsie vir energieberging. Hierdie tipe vliegwiele is reeds suksesvol aangewend vir spanningsbeheer op elektriese spoornetwerke en om oorbruggingskrag te voorsien aan rugsteun sisteme. Meer onlangs is hulle ook nuttig bewys vir die regulasie van frekwensie op die elektrisiteit netwerk. Grootskaalse aanwending van vliegwiele kan egter slegs oorweeg word indien die hoë koste van die tegnologie aangespreek word. Een van die onderliggende redes vir die hoë koste van vliegwiele is die relatiewe lae digtheid waarby energie geberg kan word, en hierdie studie ondersoek die redes hiervoor. Die ontwerpmetodiek wat in die beskikbare literatuur voorgestel is, word krities geanaliseer en ’n paar verbeteringe word aanbeveel. Mees noemenswaardig is die opmerklike verbeteringe in energie-digtheid wat soms moontlik is indien die optimerings-probleem deurdag geformuleer word. Omdat materiaaleienskappe ’n bepalende invloed op energie digtheid uitoefen word die probleem van materiaalseleksie ook verder bespreek. ’n Paar riglyne vir die seleksie van ’n optimale stel materiale sonder om oordrewe berekenings-inspanning te veroorsaak, word aan vliegwielontwerpers gegee. Hierdie voorstelle kan hopelik in die toekoms verder deurgetrap word as onderwerp vir verdere studies.
32
Droz, Christophe. "Guidage des ondes d'ordre élevé dans les composites : application au dégivrage en vol des pales d'hélicoptères." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0026.
Full textAbstract:
Lorsqu’un hélicoptère opère dans des conditions givrantes extrêmes, l’accumulation de glace sur les pales peut considérablement impacter les performances de l’appareil. De nombreuses recherches portant sur le développement d’un système de dégivrage à faible consommation et moindre coût ont été initiées ces dernières années. Dans cette thèse, une technique ondulatoire de protection contre la formation de glace sur les surfaces des pales d’hélicoptères est étudiée. La stratégie proposée repose sur l’utilisation d’ondes guidées d’ordre élevé spécifiques pour créer des cisaillements dépassant la force d’adhésion surfacique d’un profil de glace. Des essais ont d’abord été menés pour réaliser le modèle E.F. d’un tronçon de pale, puis une stratégie de réduction de modèle est développée pour la Méthode des Éléments Finis Ondulatoires. Cette formulation s’appuie sur la projection des vecteurs d’état sur une base réduite, constituée des formes d’ondes progressives. Elle permet de réaliser des analyses ondulatoires large-bande dans les structures complexes, 1D ou 2D périodiques. Les ondes guidées sont d’abord examinées dans la pale d’hélicoptère, puis les effets de localisation et de conversion des ondes sont interprétés dans divers guides d’ondes 1D et 2D. Les interactions de ces ondes d’ordre élevé avec les profils d’accrétion de glace, ainsi qu’avec plusieurs types de singularités structurelles, sont analysées au moyen d’une Méthode des Matrices de Diffusion. Une formulation ondulatoire temporelle est ensuite proposée pour l’analyse rapide de la propagation d’un train d’ondes dans les guides d’ondes couplés. Enfin, un réseau d’actionneurs est conçu pour la génération de trains d’ondes d’ordre élevé, et des validations temporelles sont réalisées dans une plaque composite ainsi que dans une pale de Super PumaWhen helicopters fly through extreme conditions, ice can aggregate on their blades and seriously affect the aircraft performances. Recently, an increasing research effort was devoted to the development of affordable low power de-icing solutions. In this thesis, a wave-based approach is adopted to prevent and/or remove ice aggregates from the surfaces of helicopter rotor blades. The de-icing strategy uses specific high-order guided waves to exceed the shear adhesion strength of ice accretion profiles. Experiments are conducted in order to update the FE model of a realistic rotor blade, then a Model Order Reduction strategy is developed for the Wave Finite Element Method. It involves a projection of the state vectors on a reduced basis of propagating waves shapes, and enables broadband wave analysis in structurally advanced 1D and 2D periodic structures. Guided wave propagation is studied within a helicopter rotor blade, and wave localization and conversion effects are discussed in various 1D and 2D composite waveguides. The interactions of high-order waves with ice aggregates and other types of structural singularities are also examined by means of a Diffusion Matrix Method. Then, time-domain propagation in coupled waveguides subjected to a wave pulse is analysed through a computationally efficient wave-based formulation. Finally, a smart actuator network is designed for the generation of high-order wave pulses and validations are conducted in a composite plate and a Super Puma rotor blade using time simulation
33
Sino, Rim. "Comportement dynamique et stabilité des rotors : application aux rotors composites." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0067/these.pdf.
Full textAbstract:
Ce travail a pour objet l'étude de la stabilité des ensembles tournants lorsque des termes d'amortissement interne (dus aux matériaux) et d'amortissement externe (paliers) sont introduits dans le modèle. La majorité des études identifiées dans la littérature sont fondées sur des développements numériques. La principale difficulté réside dans l'évaluation des paramètres physiques de l'amortissement interne qui permettent une prédiction des instabilités potentielles avec une précision suffisante. Afin de considérer des propriétés mécaniques réelles en terme d'amortissement interne, un modèle rhéologique de solide viscoélastique associé à une approche générale éléments finis de type poutre est développée, incluant les effets de cisaillement transverse. Après une description théorique (choix du modèle d'amortissement interne et équations du mouvement), une première application valide la méthode proposée. L'influence de l'amortissement sur les fréquences et les seuils d'instabilité est analysée via une étude paramétrique. Les résultats sont comparés à ceux obtenus à partir d'une approche analytique et à partir des expérimentations en rotation. Une seconde application s'intéresse à la stabilité dynamique d'un rotor composite avec prise en compte de l'amortissement avec prise en compte de l'amortissement interne et du cisaillement transverse. Une théorie simplifiée d'homogénéisation de poutre (SHBT : Simplified Homogenized Beam Theory), associée à une formulation éléments finis est introduite et utilisée pour évaluer les fréquences naturelles et les seuils d'instabilité. Cette théorie est comparée avec d'autres théories issues de la littérature (EMBT : Equivalent Modulus Beam Theory), EMBT modifié et (LBT : Layerwise Beam Theory). Une étude qualitative montre l'influence de différents paramètres (orientations, séquences d'empilement, etc. . . ) ainsi que les effets du cisaillement transverse lorsque ce dernier est introduit dans le modèle. Les effets associés sont traduits directement en terme de fréquences et de seuils d'instabilité de la structure tournante lorsque des empilements symétriques aussi bien qu'asymétriques sont considérésThis work deals with the study of dynamic instabilities within rotating assemblies due to internal damping effects. In order to consider realistic mechanical properties, in terms of internal damping, a rheological model is associated to a general finite element beam approach, including transversal shear. After a description of the theoretical background (choice of internal damping model and equations of motion), a first application illustrates the ability of the proposed model. The influence of damping on frequencies and on instability thresholds is investigated using a parametric study. Results are compared to those obtained from an analytical approach as well as from experiments. A second application is concerned with the dynamic instability of an internally damped rotating composite shaft. A Simplified Homogenized Beam Theory (SHBT), which takes into account internal damping, is introduced and then used to evaluate natural frequencies and instability thresholds. The results are compared to those obtained by using an Equivalent Modulus Beam Theory (EMBT) widely used in the literature, a Modified Equivalent Modulus Beam Theory and a Layerwise Beam Theory (LBT). The influence of laminate parameters: stacking sequences, fiber orientation and transversal shear effect on natural frequencies and instability thresholds of the shaft is studied via a parametrical study. This parametric study shows that shaft instability thresholds can be very sensitive to all these parameters
34
Sino, Rim Jacquet-Richardet Georges. "Comportement dynamique et stabilité des rotors application aux rotors composites /." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=sino.
Full text
35
Hufenbach, W., M. Gude, B. Zhou, and L. Kroll. "Stress and failure analysis of thick-walled conical composite rotors." Sage, 2004. https://publish.fid-move.qucosa.de/id/qucosa%3A38442.
Full textAbstract:
The high specific strength and stiffness of composite materials, as well as the possibility of creating a load-adapted property profile of them are ideally suited for the design of high-speed lightweight rotors. With respect to a load-adapted reinforcement structure of composite rotors, the rotor geometry has a significant influence on the optimum fibre orientation. In the case of conical rotors—the structural behaviour is strongly influenced by centrifugally induced bending effects in the rotor structure, which cause complex three-dimensional stress states in combination with the ordinary tangential and radial stresses. For analysis of the resulting complex stress states, an analytical method has been developed and verified numerically as well as experimentally. The novel method presented here is the basis for a realistic failure analysis and, in particular, serves as an efficient tool for extensive parameter studies and optimizations within the design process.
36
Shang, Xiaoyang. "Aeroelastic stability of composite hingeless rotors with finite-state unsteady aerodynamics." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12543.
Full text
37
Hayes, Daniel E. E. "The effects of porosity on the friction and wear of carbon-carbon composite aircraft brakes." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/34822.
Full textAbstract:
Six sets of subscale carbon–carbon composite rotors and stators for aircraft brakes were manufactured to provide friction and wear test samples at six different densities. The friction and wear tests used energies to represent the service energy of the Boeing 767 aircraft. A functional relationship between fiction coefficient and porosity/density was made. This relationship was used to minimise manufacturing cost by providing the minimum densification of the carbon–carbon composite brake discs needed to meet design friction coefficient.
38
Marchand, Marc Pierre. "Static and dynamic balancing of high speed fibre composite rotors." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4929.
Full text
39
Vennam, Sandeep. "Hygrothermal effects on free vibration characteristics of rotating composite beams." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4969.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-72).
40
Bao, Jinsong. "Development of Mach scale rotors with composite tailored couplings for vibration reduction." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2085.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
41
Rancourt, David. "Analyse structurelle et validation expérimentale d'un Rim-Rotor Rotary Ramjet Engine (R4E)." Mémoire, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/1612.
Full textAbstract:
Le Rim-Rotor Rotary Ramjet Engine (R4E) est un moteur très haute densité de puissance utilisant des statoréacteurs en rotation pour produire un couple à grande vitesse angulaire.Le design structurel d'une première génération de R4E est présenté dans ce mémoire ainsi qu'une validation expérimentale avec combustion haute température. Ces travaux s'imbriquent dans un programme de recherche où l'objectif ultime est de démontrer expérimentalement qu'il est possible de produire de la puissance positive de ce type de moteur. La structure principale du moteur est basée sur l'utilisation d'un Rim-Rotor, un anneau de Carbone-PEEK unidirectionnel, qui reprend partiellement le chargement des propulseurs en compression. Un moyeu en aluminium en une pièce inclut les propulseurs et supporte le système d'allumage inductif intégré à la structure. Ce dernier a été caractérisé indépendamment afin de connaître l'effet des paramètres tels la distance entre les électrodes sur la puissance et l'énergie des étincelles.Le concept final proposé pèse 76 g, ne contient que 5 pièces dans un assemblage unique et peut résister à une vitesse tangentielle de 330 m/s (120 krpm) au niveau des propulseurs lors d'une combustion d'hydrogène de 1 sec. Un autre concept présenté est conçu pour résister 560 m/s (200 krpm) pour des durées de combustion très courtes, sans échauffement significatif des composants. Un modèle structurel analytique est proposé et validé par un modèle numérique ainsi que des essais expérimentaux sans combustion réalisés jusqu'à 188 krpm sans rupture.Le prototype conçu pour la combustion est validé par rapport à ses paramètres de conception et une rupture des pales de turbine survient tel que prédit par le modèle couplé thermique-structurel numérique. Les recherches ont démontré que le concept d'un R4E est viable et qu'il a le potentiel d'atteindre une vitesse tangentielle de près de 1000 m/s en utilisant des matériaux disponibles aujourd'hui. Les dissimilitudes d'expansion thermique entre les composantes, la différence de rigidité entre les pièces de l'assemblage ainsi que le transfert de chaleur vers le Rim-Rotor ont été identifiés comme des considérations importantes pour les futurs concepts de R4E.
42
Simon, Fabrice. "Moteur couplé supraconducteur à aimants permanents." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0149.
Full textAbstract:
L'apparition dans les années 80 de semi-conducteurs fonctionnant aux fréquents industrielles avec de très faibles pertes a relancé l'étude des machines supraconductrices. L'association d'un induit supraconducteur statique avec un inducteur à aimants permanents conduit à des moteurs couples robustes. Ces structures hybrides très compactes et légères sont destinées aux systèmes embarqués qui nécessitent de forts couples massiques. Les essais menés sur une maquette de petite puissance ont validé le concept et les calculs théoriques. Pour tirer des conclusions sur cette structure hybride originale il convenait de concevoir, construire et tester une machine de taille significative. L'objet de cette thèse est l'étude de définition de ce démonstrateur de 150 kW à 400 tr/min. En vue de la construction, une étude des matériaux utilisés a été menée, notamment sur les composites en fibres de verre. Les contraintes thermiques expliquent la structure, dite air, des moteurs hybrides. Après une réflexion sur la réalisation de l'induit et l'inducteur, la machine a été calculée à partir d'un programme d'optimisation pour maximiser le rendement rapport au couple massique. Le démonstrateur présente de bonnes caractéristiques, principalement limitées par la cryogénie. De nombreuses simulations numériques avec le programme d'éléments finis flux ont permis de mieux apprécier les caractéristiques de la machine. Enfin, l'extrapolation à de plus forts couples donne une idée du seuil de compétitivité de ces moteurs hybrides et gains possibles en termes de poids, encombrement et rendement. Une comparaison avec une solution classique a été menée pour la chaîne de traction du T. G. V.
43
Chaudhary, Sumeet. "Lightweight Electromagnetic Induction Motor." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1581333548692675.
Full text
44
Schliesman, Michael Dean. "Improved testing methods for measurement of extension-twist coupling." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18862.
Full text
45
Tawk, Issam. "Contribution à la modélisation à l'impact de pales d'hélicoptère." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/503/.
Full textAbstract:
Cette étude est une contribution à la modélisation à l'impact de pales d'hélicoptère. Des essais d'impact sur des tronçons de pales ont été réalisés à différents niveaux d'énergies, à l'aide d'un canon à gaz comprimé. Ces essais ont permis de dresser l'état des endommagements en fonction de la vitesse d'impact. Des essais complémentaires ont montré que la structuration de la stratification et le renforcement de la peau modifie le comportement à l'impact de la pale. Une méthode de modélisation est développée sur le code explicite RADIOSS. Il s'agit de gérer la dégradation du bord d'attaque qui apparaît sous la forme d'une rupture de la résine et apparition des paquets de fibres en modélisant la résine par des éléments 3D endommageables et les paquets de fibres par des éléments 1D. La modélisation des décollements est réalisée par une couche d'éléments endommageables de faibles dimensions. Pour enrichir la modélisation proposée et afin de prendre en compte tous les types de décollement observés expérimentalement, une approche locale globale pour la modélisation du délaminage est développée. Cette approche construite sur un élément de volume spécifique PEC est basée sur la méthode de VCCT. Elle est validée à travers la simulation des différents essais de poutre DCB, ELS, ENF et ADCBThis study is a contribution to the modelling of impact on helicopter blades. Experimental tests of impact were made with a compressed gas gun on sections of blades at different levels of energy. These tests were used to establish the damage in terms of impact velocity. Additional tests showed that the stratification and the reinforcement of the skin change the behaviour of the blade during the impact. A modelling approach is developed with the finite element code RADIOSS. It consists in controlling the degradation of the front edge that appears by a break of the resin and by the appearance of bundles of fibers. This approach is realised by modelling the resin with 3D damaged elements and the bundles of fibers by 1D elements. Delamination was modelled with a thin layer of damaged elements. To enrich the proposed modelling and to take into account all types of delamination observed experimentally, a local global approach for modelling the delamination is developed. This approach, built with the use of a specific 3D element PEC, is based on the VCCT method. It is validated through the simulation of different beam tests DCB, ELS, ENF and ADCB
46
Lobo, Candido Jorge de Sousa. "Estudo sobre a utilizaÃÃo do rejeito do granito rosa iracema como matÃria-prima na fabricaÃÃo de funis de saÃda da fiaÃÃo a rotor na indÃstria tÃxtil." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=3313.
Full textAbstract:
O presente trabalho foi motivado pela necessidade de minimizar impactos ambientais causados pela extraÃÃo de granito, dando aplicabilidade aos rejeitos da indÃstria de rochas ornamentais. Trabalhos anteriores mostraram a viabilidade de se utilizar esses rejeitos na produÃÃo de guia-fios cerÃmicos para a IndÃstria TÃxtil. Um outro componente, bastante utilizado na IndÃstria TÃxtil à o funil de saÃda da fiaÃÃo a rotor. O elevado custo de importaÃÃo desses componentes torna bastante atrativo a busca de materiais alternativos para sua fabricaÃÃo no PaÃs. AnÃlises preliminares mostraram que esses funis sÃo compostos basicamente de alumina, com resistÃncia mecÃnica muito superior ao dos resÃduos de granito que se pretendia utilizar, levando à necessidade de se reforÃar o material. PartÃculas de alumina foram incorporadas Ãs amostras formando compÃsitos dos quais foram estudadas diversas composiÃÃes de matriz e reforÃo para se obter caracterÃsticas aproximadas daquelas dos funis comerciais. Foram realizadas analises de caracterizaÃÃo dos materiais envolvidos, e ensaios para determinaÃÃo das propriedades fÃsicas. As amostras com 30% e 40% em peso do reforÃo de alumina resultaram em uma melhor sinterizaÃÃo e resultados de dureza com 81% dos valores obtidos pelos funis comerciais, com uma rugosidade prÃxima da exibida por aqueles componentesThe present work was motivated by the need to minimize environmental impacts caused by granite quarrying. One of the ways to achieve this objective is to find value-added technical applications for granite residues. In a previous work it has been demonstrated that these silica-rich granite powders can be employed as raw-materials for the production of textile thread-guides. One very promising application for the textile industry in Brazil is the fabrication of open end navels. These are high-cost components made from expensive technical ceramics, which are imported from Europe. Therefore, it would be very interesting to be able to produce them at a lower cost, using residual granite powders. Preliminary analysis of the materials of commercially available textile navels has shown that they are composed mainly of alumina. Under normal conditions, alumina-made components exhibit much higher mechanical strength and hardness than silica-made components. Thus, it is necessary to introduce reinforcements to the starting granite powder used in this work (a residue obtained form the commercial stone âRosa Iracemaâ), in order to improve the performance of the parts made from it. Different amounts of submicrometric alumina particles were added to the starting powder, rendering composites. These composites were submitted to several mechanical and physical analysis aiming at finding the best combination of properties, compared to the properties of the commercially available textile navels. Test pieces containing 30% and 40%wt alumina gave the best results in terms of sinterability, and surface roughness. Their hardness was approximately 80% of the hardness of the alumina navels
47
Ripoll, Masferrer Lluís. "Análisis y diseño de volantes de inercia de materiales compuestos." Doctoral thesis, Universitat Politècnica de Catalunya, 2006. http://hdl.handle.net/10803/6415.
Full textAbstract:
Los volantes de inercia superan a las baterías eléctricas por su capacidad de absorber y ceder energía en poco tiempo y, si se fabrican con materiales compuestos, también por su reducido peso. La tesis presenta un estudio sobre los rotores de materiales compuestos aplicados a los acumuladores cinéticos para hacerlos más asequibles a usos industriales baratos. Para ello se proponen dos objetivos: obtener un sistema analítico de cálculo, y mejorar el diseño de rotores de bajo coste.Se desarrolla un sistema analítico de cálculo muy completo, tanto en las cargas como en las tensiones. Se consideran todas las cargas necesarias para el diseño mecánico del rotor: la fuerza centrífuga, la fuerza de aceleración y las tensiones residuales, térmica y de hidratación; y se determinan todas las componentes, normales y cortantes, de la tensión para cada punto del rotor.
El cálculo en condiciones de tensión plana, utilizado por la mayoría de autores, se amplía con el cálculo en deformación axial constante, que es una variante mejorada de la deformación plana. Se comprueba que sus resultados son mejores que los de tensión plana cuando se comparan con los obtenidos en modelos de elementos finitos. Paralelamente, como aportación nueva de la tesis, se deducen las funciones de la variación de la tensión axial y de la tensión cortante radial-axial a lo largo del eje longitudinal del rotor. A partir de estos resultados se desarrolla un sistema general de cálculo que, además de unificar los sistemas de tensión plana y deformación axial constante, permite determinar todas las tensiones en cualquier posición radial-axial del rotor.
Este sistema unificado de cálculo se amplia con tres particularidades: una aplicación de cálculo para resolver rotores multicapa, las ecuaciones especiales para los materiales singulares no resolubles con las ecuaciones generales, y el cálculo de capas con fibras orientadas axialmente aplicadas para refuerzo en configuraciones especiales.
Con el objeto de mejorar las prestaciones del rotor se estudian dos procedimientos para crear tensiones de pretensado: generando tensiones durante el bobinado y utilizando las tensiones residuales térmicas. En el primero se elabora un sistema analítico de cálculo para determinar las tensiones residuales de bobinado y se complementa con una simulación mediante elementos finitos basada en submodelos incrementales. Ambos cálculos son capaces de simular el material no curado aplicando las propiedades viscoelásticas de los ensayos experimentales de otros autores. En el segundo se presenta un sistema nuevo, denominado pretensado térmico, basado en el curado por etapas, que genera tensiones residuales parecidas a las de bobinado pero con menos problemas de fabricación.
El diseño de volantes se aplica a tres configuraciones básicas: rotores híbridos multicapa con materiales de rigidez progresiva, rotores de un solo material con anillos de elastómero y rotores con pretensado térmico.
Sus prestaciones se valoran con tres variables: la masa, el volumen y el coste del material; de las cuales el coste es la principal y se utiliza para la optimización de la geometría.
En cada configuración se determina la energía máxima para distintas relaciones de radios del rotor y se compara con el rotor de un sólo material. Se utilizan los materiales básicos usados en la fabricación de rotores: la fibra de carbono con matriz epoxi, la fibra de vidrio con matriz epoxi, el aluminio y el acero. Los dos materiales compuestos ofrecen mejores resultados que los metales, pero disminuyen sensiblemente en rotores con espesor de pared grande. En estos casos, la energía por unidad de coste mejora aplicando los anillos elásticos y el pretensado térmico.
Flywheels are better than electric batteries in that they absorb and yield energy in shorter time and, if made out of composite materials, also in that they weight less. This thesis presents a study of composite material rotors applied to kinetic accumulators in order to make them usable for low cost general industrial uses. Two objectives are proposed: a) to develop an analytical system for computation and b) to design alternatives in order to improve the performance on low-cost rotors.
The analytical system is intended to be very complete, considering all relevant types of external loads and stress components. For the former, centrifugal, acceleration forces and residual, thermal and moisture stresses are included. For the latter, five normal and shear components are computed at each point of the rotor.
The usual plane stress condition is expanded with the consideration of constant axial strain, along the lines of the plane strain hypothesis but with greater accuracy. It is shown that the current theory results fit the ones from finite elements much better than those from plain stress. As a new contribution, the functions for the axial stress and the radial-axial stress along the axis of the rotor are developed. From these results, a general system that unifies the plane stress and constant axial strain can compute the stress state at any position.
In addition, the unified system includes three novel aspects: an extension of computation for multi-layer rotors, special equations for some materials in which behaviour present singularities and the computation of layers with fibers along the axial direction, which can be useful as a reinforcement for some configurations.
Two procedures that can create beneficial residual stresses are studied: generating stresses during the filament winding and using the thermal stresses. For the first, analytical expressions are developed and validated and complemented with especially developed finite elements based on incremental submodels. In both cases the material is characterized by viscoelastic properties taken from the literature. For the second, a new procedure called thermal prestress is based on the accumulation of partial curing processes (by stages), which is able to create residual stresses similar to those of winding but involving simpler manufacturing.
Three basic configurations are studied for the design: hybrid rotors with progressive stiffness along the radius, single material rotors with elastomer thin rings and rotors manufactured with thermal prestress, evaluating the performance as a function of the mass, volume and cost of the material. The latter is defined as the most important, and it is used as a reference for the geometry optimization.
The maximum energy stored on each of the configurations is compared with that of a single material rotor, using the most common ones: glass and carbon fiber both with epoxy matrix, aluminium and steel. Results show that glass/epoxy has the highest storing capability per unit cost, although the number is greatly reduced when the thickness increases. If this rotor has a thin layer of carbon/epoxy, the capability does not increase, although it does with distributed elastomeric layers. There is also an increase with fabrication based on the thermal prestress technique.
48
Thierry, Olivier. "Réduction des vibrations de structures composites complexes par dispositifs piézoélectriques shuntés : application aux aubes de turbomachines." Thesis, Paris, CNAM, 2016. http://www.theses.fr/2016CNAM1111/document.
Full textAbstract:
Cette thèse CIFRE (Conventions Industrielles de Formation par la REcherche), en collaboration avec Safran Aircraft Engines, concerne la réduction des vibrations de flexion en basse fréquence d'une aube de rotor de soufflante en matériau composite. L'intérêt premier est de réduire les marges au flottement en augmentant l'amortissement des aubages pour permettre l'utilisation des moteurs dans des plages de fonctionnement à haut rendement actuellement inexploitées. Les autres avantages directement liés à la réduction de vibration sont l'augmentation de la durée de vie des pièces ainsi que la réduction du bruit du moteur. L'objet de cette étude, est d'étudier différents dispositifs d'amortissement de vibrations piézoélectriques, en basses fréquences, applicables à une aube de turbomachine fabriquée en matériaux composites. Les applications principalement visées sont des aubes de rotor de soufflante ou des pales de rotor non caréné ("open-rotor"), de géométrie élancée et complexe. Les solutions étudiées utilisent des éléments piézoélectriques couplés à un circuit électrique passif ou semi-passif. Le coeur de ce travail de thèse, encore un verrou scientifique à l'heure actuelle, est de proposer des solutions performantes qui intègrent les éléments piézoélectriques aux aubes de soufflante afin de respecter les contraintes aérodynamiques imposées pour ce type de structure, tout en augmentant l'amortissement sur un des premiers modes de vibration. Les performances de ce genre de dispositifs sont directement liées à une grandeur : le facteur de couplage électromécanique, qu'il s'agit de maximiser. Il dépend de toutes les caractéristiques de la structure : les matériaux utilisés (structure composite hôte, matériau piézoélectrique), mais surtout du placement et de la géométrie des éléments piézoélectriques. L'utilisation de matériaux piézoélectriques connectés à des circuits actifs, semi-passifs ou passifs a été largement étudiée mais les expériences traitent presque toujours de cas académiques de poutres ou de plaques. L'objectif est ici, pour le dispositif piézoélectrique développé, de pouvoir évaluer les performances des shunts en terme d'atténuation sur une structure massive faiblement amortie. Une partie du travail consiste ainsi à bâtir un modèle éléments finis prédictif de la structure composite couplée aux matériaux piézoélectriques, en vue de quantifier les performances du dispositif. Plusieurs solutions sont testées sur une structure simple pour évaluer l'influence sur les performances du dispositif, (1) du choix du matériau piézoélectrique, (2) du placement et de la géométrie des éléments piézoélectriques ainsi que (3) du circuit électrique dissipatif. Différentes solutions d'intégration à l'aube sont proposées et une méthode de caractérisation des propriétés des matériaux tissés est développée dans la perspective d'intégrer les matériaux actifs à la préforme du composite. Cette étude est à la fois numérique et expérimentale : un démonstrateur, utilisant une aube en matériaux composites est conçu puis testé en laboratoire pour valider les concepts proposésThis thesis concerns the vibration reduction in the low frequency range of a composite fan blade of a turbojet engine with piezoelectric devices. The interest is to increase lifespan and avoid flutter phenomena by reducing the vibration amplitude. The purpose of this thesis is to study several shunted piezoelectric devices, in the low frequency range, that can be applied to a woven composite turbojet fan blade. The targeted applications are the LEAP fan blades or the “open-rotor” fan blade, both of them required to manage a complex geometry. The solutions investigated used piezoelectric elements coupled to a passive or semi-passive circuit. The core of this thesis, still a scientific obstacle at present, is to propose efficient solutions that integrate the piezoelectric elements to the fan blades in order to meet aerodynamic constraints for this type of structure, while increasing damping level on one of the first modes of vibration. The performances of such devices are directly related to a coefficient: the electromechanical coupling factor that requires to be maximized. This coefficient depends on all the features of the structure: materials used (host composite structure, piezoelectric material), but especially the placement and geometry of the piezoelectric elements. The use of piezoelectric material connected to active, semi-passive or passive circuits has been extensively studied but the experiences almost always deal with academic cases such as beams or plates. The aim is for the developed piezoelectric device, to evaluate the damping performance of a weakly damped massive structure.A part of the work is thus to develop a predictive finite element model of the structure coupled to the piezoelectric material to quantify the performance of the device. Several solutions are tested on a simple structure to evaluate the influence on the device performance of, (1) the choice of the piezoelectric material, (2) the placement and geometry of the piezoelectric elements, and (3) of the dissipative circuit. Various integration solutions in the blade are proposed and a method for characterizing the properties of woven materials is developed in the perspective of integrating the active materials in the composite preform.This study is both numerical and experimental: a demonstrator using a composite fan blade is designed and tested in the laboratory to validate the proposed concepts
49
ROCHA, Adi Neves. "Conversor estático de 9 chaves acionando máquina hexafásica." Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/442.
Full textAbstract:
Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-20T22:15:13Z
No. of bitstreams: 1
ADI NEVES ROCHA - DISSERTAÇÃO PPGEE 2014..pdf: 4213060 bytes, checksum: 41dbc9ec6203a02fc678bc1c878970dc (MD5)Made available in DSpace on 2018-04-20T22:15:13Z (GMT). No. of bitstreams: 1 ADI NEVES ROCHA - DISSERTAÇÃO PPGEE 2014..pdf: 4213060 bytes, checksum: 41dbc9ec6203a02fc678bc1c878970dc (MD5) Previous issue date: 2014-08-08
O objetivo do estudo apresentado nessa dissertação é analisar e comparar dois inversores fonte de tensão acionando uma máquina de indução hexafásica. as estruturas analisadas são: o conversor composto de seis braços possuindo dois dispositivos semicondutores por braço (12 chaves) e um conversor composto de três braços e nove dispositivos semicondutores (9 chaves). A estrutura composta por 12 chaves é a configuração padrão para acionamento de cargas hexafásicas . Analisando quanto ao aspecto da quantidade de chaves o conversor de 9 chaves apresenta uma evidente redução do número de componentes. Neste trabalho busca-se uma comparação mais fundamentada a partir da análise destas topologias com relação a outras características, tais como: (i) estrutura ou modo de conexão dos dispositivos com a descrição das limitações de cada estrutura; (ii) diferenças nas técnicas de modulação empregadas; (iii) níveis de corrente e tenção em cada um dos dispositivos que compõem a estrutura; (iv) análise do desempenho segundo a quantidade de perdas por condução e por chaveamento; (v) análise de desempenho quanto aos níveis de dispersão harmônica. Apesar da análise estar voltada para a comparação dos conversores, há uma descrição da máquina hexafásica modelada por decomposição vetorial e a aplicação de uma estratégia de controle no acionamento da máquina, utilzando a técnica de controle por fluxo rotórico.
The goal of the study presented in this thesis is to analyze and compare towo voltage source inverters driving a six-phase induction machine. The types of structures analyzed are: the converter of six legs having two semiconductor devices per leg (12 switches) and an inverter composed of three legs - (nine semiconductor devices 9 switches). The converter of 12 switches is the default configuration for driving six-phase loads. Analyzing the numbers of switches aspects, the 9 switches converter shows a clear reduction in the number of components. This paper seeks a more reasoned comparison from the analysis of these topologies with respect to other characteristics, such as: (i) structure or way of connecting devices to the description of the limitations of each structure; (ii) differences in the modulation techniques employed ; (iii) levels of current voltage in each of the devices of the structure; (iv) analysis of performance depending on the amount of conduction and switching losses; (v) performance analysis of the levels of harmonic distortion. Althought the analysis is focused on the comparison of the converters, there is a description of the six-phase machine modeled by vector decomposition and implementation of a control strategy to drive the machine using the rotor flux control technique.
50
Hou, Zhicheng. "Modeling and formation controller design for multi-quadrotor systems with leader-follower configuration." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2259/document.
Full textAbstract:
Cette thèse propose des solutions aux problématiques inhérentes au contrôle de formations aériennes de type leader-suiveur pour des flottes de quadrirotors. Au regard des travaux existants, les stratégies qui sont proposés dans notre travail, considère que le(s) leader{s) a une interaction avec les suiveurs. En outre, les rôles de leader et de suiveur sont interchangeables lors de la formation. Dans un premier temps, la modélisation mathématique d'un seul quadrirotor et celle de la formation de quadrirotors est développée. Ensuite, le problème de suivi de trajectoire pour un seul quadrirotor est étudié. Au travers de l'analyse de 1, dynamique du système pour la conception d'une commande par platitude, il apparait que le suivi de trajectoire pour chaque quadrirotor équivaut à déterminer les sorties plates désirées. Un contrôleur pour système plats permettant l'asservissement des drones pour le suivi de trajectoire est donc proposé. Étant donné la propriété de double-boucle de la dynamique du quadrirotor en boucle fermée, un contrôleur d'attitude avec des grands gains est conçu, selon la théorie « singular perturbation system ». Puisque la dynamique du quadrirotor en boucle fermée fonctionne sur deux échelles de temps, la dynamique de rotation (boundary-layer mode) est contrôlée sur l'échelle de temps la plus rapide. La conception du contrôleur de formation dépend seulement de la dynamique de translation (modèle réduit dans une échelle de temps lente). Ce résultat a simplifié la conception du contrôleur de formation, de telle sorte que le modèle réduit du quadrirotor est utilisé au lieu du modèle complet. Étant donné que le modèle réduit du quadrirotor a une caractéristique de double-intégrateur, un algorithme de consensus pour des systèmes caractérisés par de multiple double-intégrateurs est proposé. Pour traiter le problème de la formation leader-suiveur, une matrice d'interaction est initialement proposée basée sur la matrice de Laplacienne. Nous montrons que la condition de convergence et la vitesse de convergence de l'erreur de formation dépendent de la plus petite valeur propre de la matrice d'interaction. Trois stratégies de contrôle de la formation avec une topologie fixe sont ensuite proposées. Le contrôle de formation par platitude est proposé pour obtenir une formation agressive, tandis que les dérivées de grands ordres de la trajectoire désirée pour chaque UAV sont estimées en utilisant un observateur; la méthode Lyapunov redesign est implémentée pour traiter les non-linéarités de la dynamique de la translation des quadrotors; une loi de commande bornée par l'utilisation, entre autre, de la fonction tangente hyperbolique est développée avec un feedback composite non linéaire, afin d'améliorer les performances de la formation. De plus, une commande de commutation saturée de la formation est étudiée, car la topologie de la formation est variable. La stabilité du système est obtenue grâce aux théories “convex hull » et « common Lyapunov function ». Cette stratégie de commande de commutation permet le changement des leaders dans la formation. Inspirée par certains travaux existants, tels que le contrôle de la formation avec des voisins anonymes, nous proposons, finalement, une loi de commande avec des voisins pondérés, qui montre une meilleure robustesse que le contrôle avec des voisins anonymes. Les résultats de simulation obtenus avec Matlab illustrent premièrement nos stratégies de contrôle que nous proposons De plus, en utilisant le langage de programmation C ++, nos stratégies sont mises en œuvre dans un framework de simulation et d'expérimentation développé au laboratoire Heudiasyc. Grâce aux nombreux tests variés que nous avons réalisés en simulation et en temps-réel, l'efficacité et les avantages de nos stratégies de contrôle de la formation proposées sont présentésIn this thesis, we address a leader-follower (L-F) formation control problem for multiple UAVs, especially quadrotors. Different from existing works, the strategies, which are proposed in our work, consider that the leader(s) have interaction with the followers. Additionally, the leader(s) are changeable during the formation. First, the mathematical modeling of a single quadrotor and of the formation of quadrotors is developed. The trajectory tracking problem for a single quadrotor is investigated. Through the analysis of the flatness of the quadrotor dynamical model, the desired trajectory for each quadrotor is transferred to the design of the desired at outputs. A flatness-based trajectory tracking controller is, then, proposed. Considering the double-loop property of the closed-loop quadrotor dynamics, a high-gain attitude controller is designed, according to the singular perturbation system theory. Since the closed-loop quadrotor dynamics performs in two time scales, the rotational dynamics (boundary-layer model) is controlled in a fast time scale. The formation controller design is then only considered for the translational dynamics: reduced model in a slow time scale. This result has simplified the formation controller design such that the reduced model of the quadrotor is considered instead of the complete model. Since the reduced model of the quadrotor has a double-integrator characteristic, consensus algorithm for multiple double-integrator systems is proposed. Dealing with the leader-follower formation problem, an interaction matrix is originally proposed based on the Laplacian matrix. We prove that the convergence condition and convergence speed of the formation error are in terms of the smallest eigenvalue of the interaction matrix. Three formation control strategies with fixed formation topology are then proposed. The flatness-based formation control is proposed to deal with the aggressive formation problem, while the high-order derivatives of the desired trajectory for each UAV are estimated by using an observer; the Lyapunov redesign is developed to deal with the nonlinearities of the translational dynamics of the quadrotors; the hyperbolic tangent-based bounded control with composite nonlinear feedback is developed in order to improve the performance of the formation. In an additional way, a saturated switching control of the formation is investigated, where the formation topology is switching. The stability of the system is obtained by introducing the convex hull theory and the common Lyapunov function. This switching control strategy permits the change of the leaders in the formation. Inspired by some existing works, such as the anonymous neighbor-based formation control, we finally propose a weighted neighbor-based control, which shows better robustness than the anonymous neighbor-based control. Simulation results using Matlab primarily illustrate our proposed formation control strategies. Furthermore, using C++ programming, our strategies are implemented on the simulator-experiment framework, developed at Heudiasyc laboratory. Through a variety of tests on the simulator and real-time experiments, the efficiency and the advantages of our proposed formation control strategies are shown. Finally, a vision-based inter-distance detection system is developed. This system is composed by an on-board camera, infrared LEDs and an infrared filter. The idea is to detect the UAVs and calculate the inter-distance by calculating the area of the special LEDs patterns. This algorithm is validated on a PC, with a webcam and primarily implemented on a real quadrotor