This project investigated the relations between recalled job-satisfaction, ability, and task demands in Vietnam era helicopter aviators. It attempted to detect and describe factors present in a dangerous combat environment which may influence some individuals to enjoy and take satisfaction at being exposed to, creating, and participating in the dangerous and life threatening violence involved in helicopter combat. Participants were 30 pilots and crew members retired from the 335th Assault Helicopter Company who were all actively involved in combat in Vietnam from 1968 to 1970. This study found that developing a love of war is correlated with anger during combat. The love of war is not correlated with PTSD processes nor is it correlated with specific personality dimensions. The love of war research is a new area. The questions were used to operationalize the love of war represent a significant limitation. This method of operationalizing the love of war concept does not make fine discriminations has questionable content validity. To facilitate accuracy in discriminating between participants when conducting future research in the area, researchers could benefit from constructing a measure with greater content validity.

This research investigates on-blade partial span active plain trailing edge flaps (TEFs)with an aim to alleviate the helicopter vibrations. Among all the available smart materials, piezoelectric stack actuator(PEA)has shown its strong candidature for full scale rotor systems. Although, PEAs are quite robust in operation, however, they exhibit rate dependent hysteresis phenomenon and can generate only very small displacements. Dynamic hysteresis is a complex phenomenon which, if not modeled, can lead to drift in the vibration predictions. In this research, a comprehensive experimental analysis is performed on a commercially available piezostack actuator, APA-500L, which is well suited for full scale applications. Rate dependent hysteresis loops are obtained for helicopter operational frequencies. Nonlinear rate-dependent hysteresis loops are modeled using conic section approach and the results are validated with experimental data. Dynamic hysteresis exhibited by the PEA is further cascaded with the helicopter aeroelastic analysis and its effect on helicopter vibration predictions is investigated. PEAs generate high force but are limited by small translational motions. A linear to rotary motion amplification mechanism is required to actuate the TEF for vibration alleviation. A smart flap is designed and developed using computer-aided-design models. A rotor blade test section is fabricated and a lever-fulcrum mechanism (AM-1) is developed for a feasibility study. Smart flap actuation is demonstrated on the rotor blade test section. The conventional motion amplification devices contain several linkages, which are potential sites for structural failure. A novel pinned-pinned post-buckled beam linear-to-rotary motion amplifier (AM-2) is designed and developed to actuate the flaps. A new design of linear-to-linear amplification mechanism (LX-4) is developed and is employed in conjunction with AM-2 to increase the flap angles by an order of magnitude. An analytical model is developed using Mathieu-Hill type differential equations. Static and dynamic tests are conducted on a scaled flap model. Helicopter aeroelastic simulations show substantial reduction in hub loads using AM-2 mechanism. To further enhance the flap angles, an optimization study is performed and optimal beam dimensions are obtained. A new technique is also proposed to actively bias the flaps for both upward and downward motion. Critical flap design parameters, such as flap span, flap chord and flap location influences the flap power requirement and vibration objective function significantly. A comprehensive parametric investigation is performed to obtain the best design of TEFs at various advance ratios. Although, parametric study equips the designer with vital information about various critical system parameters, however, it is a computationally expensive exercise especially when used with large comprehensive helicopter aero elastic codes. A formal optimization procedure is employed to obtain the optimal flap design and location. Surrogate models are developed using design of experiments based on response surface methodology. Two new orthogonal arrays are proposed to construct the second order polynomial response surfaces. Pareto analysis is employed in conjunction with a newly developed computationally efficient evolutionary multi-objective bat algorithm. Optimal flap design and flap locations for dual trailing edge flaps are obtained for mutually conflicting objectives of minimum vibration levels and minimum power requirement to actuate the flaps.

Incorporating uncertainties in the aeroelastic analysis increases the confidence levels of computational predictions and reduces the need for validation with experimental or flight test data. Helicopter rotor blades, which play a dominant role in the overall vehicle performance, are routinely made of composites. The material properties of composites are uncertain because of the variations in manufacturing process and other effects while in service, maintenance and storage. Though nominal values are listed, they are seldom accurate. In this thesis, the effect of uncertainty in composite material properties on the computational predictions of cross-sectional properties, natural frequencies, blade tip deflections, vibratory loads and aeroelastic stability of a four-bladed composite helicopter rotor is studied. The effect of material uncertainty is studied with the composite rotor blades modeled as components of soft-inplane as well as stiff-inplane hingeless helicopter rotors. Aeroelastic analysis based on finite elements in space and time is used to evaluate the helicopter rotor blade response in hover and forward flight. Uncertainty analysis is performed with direct Monte Carlo simulations based on a sufficient number of random samples of material properties. It is found that the cross-sectional stiffness parameters and natural frequencies of rotor blades show considerable scatter from their baseline predictions. The uncertainty impact on the rotating natural frequencies depends on the level of centrifugal stiffening of each mode. The propagation of material uncertainty into aeroelastic response causes large deviations from the baseline predictions. The magnitudes of 4/rev vibratory loads show deviations of 10 to 600 percent from their baseline predictions. The aeroelastic stability in hover and forward flight conditions also show considerable uncertainty in the predictions. In addition to the effects of material uncertainty, various factors influencing the propagation of material uncertainty are studied with the first-order based reliability methods. The numerical results have shown the need to consider the uncertainties in the helicopter aeroelastic analysis for reliable computational predictions. Uncertainty quantification using direct Monte Carlo simulation is accurate but computationally expensive. The application of response surface methodologies to reduce the computational cost of uncertainty analysis is studied. Response surface approximations of aeroelastic outputs are developed in terms of the composite material properties. Monte Carlo simulations are then performed using these computationally less expensive response surface models. The results of this study show that the metamodeling techniques can effectively reduce the computational cost of uncertainty analysis of composite rotor blades. In the last part of the thesis, an aeroelastic optimization method to minimize the vibration level is developed with due consideration to material uncertainty. Second-order polynomial response surfaces are used to approximate the objective function which smooths out the local minima or numerical noise in the design space. The aeroelastic optimization is carried out with the nominal values of composite material properties and the performance of final design is found to be optimum even for the perturbed values of material properties.

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.

Au cœur des moyens de transport, de transformation d'énergie, et de biens d'équipements, les machines tournantes peuvent avoir des comportements dynamiques complexes dus à de multiples sources de non linéarités liées aux paliers hydrodynamiques, à la présence de fissures, aux touches rotor-stator, ... Des phénomènes comme les décalages fréquentiels et donc de vitesses critiques, les cycles d'hystérésis avec sauts d'amplitudes, le changement brutal du contenu fréquentiel des réponses, sont des expressions de ces comportements. Résoudre les équations du mouvement induites par des modélisations avec des éléments finis de type poutre ou volumique, pour calculer les réponses à des sollicitations diverses (comme le balourd ou le poids propre), est réalisable avec des méthodes d'intégration pas à pas dans le temps mais au prix de temps de calcul prohibitifs. Cela devient particulièrement préjudiciable au stade du pré-dimensionnement où il est nécessaire de réaliser rapidement des études paramétriques. Aussi une alternative intéressante est de mettre en {\oe}uvre une méthode numérique, à la fois générale et efficace pour analyser la réponse non linéaire des rotors en régime stationnaire. La démarche proposée combine, dans un premier temps, la méthode de la balance harmonique (HBM) et la technique de bascule Temps-Fréquence (AFT) afin d'obtenir rapidement dans le domaine fréquentiel les réponses périodiques des rotors à grand nombre de degrés de liberté apportés par les éléments finis volumiques. Puis, l'association à la méthode de continuation par pseudo-longueur d'arc aboutit à établir continûment l'ensemble des solutions d'équilibre dynamique sur la plage de vitesse de rotation. Enfin la stabilité dynamique locale de la solution périodique est analysée grâce à des indicateurs de bifurcation basés sur l'évolution des exposants de Floquet. Ainsi sont détectées les bifurcations de branches de solutions périodiques de type point limite, point de branchement et notamment Neimark-Sacker. Leur localisation est déterminée précisément en résolvant un système augmenté constitué de l'équation du mouvement et d'une équation supplémentaire caractérisant le type de bifurcation considéré. En déclarant un paramètre du système (coefficient de frottement, jeu rotor/stator, amplitude de l'excitation,...) comme nouvelle variable, l'utilisation de la technique de continuation conjointement avec le système augmenté détermine directement le cheminement des bifurcations en fonction de ce paramètre sur la nappe des réponses non linéaires. Les suivis de bifurcations délimitent les zones de fonctionnement spécifiques, extraient efficacement l'essentiel du comportement dynamique et offrent ainsi une nouvelle approche pour dimensionner de façon efficace les systèmes notamment en rotation. Nombre des développements réalisés sont implantés dans le code de calcul Cast3M. / Generally speaking, the rotating systems utilized in the energy production have a small rotor-stator gap, are able to run during long periods, and are mounted on hydrodynamic bearings. Rotor-stator interactions in case of blade loss, crack propagation due to fatigue, and a variable stiffness due to the nonlinear restoring forces of the bearings can make the rotordynamics nonlinear and the responses complicated: significant amplitude and frequency shifts are introduced, sub- and super-harmonics appear, and hysteresis occurs. It is of great importance to understand, predict and control this complicated dynamics. Due to the large number of DOFs and the broad range of study frequency, the computation time for solving the equations of motion by a temporal integration method can be quite prohibitive. It becomes particularly disadvantageous at the design stage where a parametrical study need to be quickly performed. An alternative numerical method, which is general and effective at the same time, is proposed in order to analyse the nonlinear response of the rotors at steady state. Firstly, the periodic responses of nonlinear rotors are calculated in the frequency domain by combining harmonic balance method (HBM) and alternating frequency-time (AFT). With the help of continuation method, all dynamic equilibrium solutions of nonlinear systems are determined for the range of study frequency. Then, Floquet exponents which are the eigenvalues of Jacobian are sought for stability analysis of periodic solutions. Then the local stability of the periodic solution is analysed through the bifurcation indicators which are based on the evolution of Floquet exponents. The bifurcations of periodic solution branch, such as limit point, branch point, and Neimark-Sacker bifurcation, are thus detected. By declaring a system parameter (friction coefficient, rotor / stator gap, excitation amplitude, ...) as a new variable, applying once again the continuation method to the augmented system determines directly the bifurcation's evolution as a function of this parameter. Thus, parametric analysis of the nonlinear dynamic behaviour is achieved, the stability boundary or the regime change boundary is directly determined. Numerous developments are implemented in the calculation code Cast3M.

Ces travaux de thèse ont été réalisés grâce à une collaboration entre Safran Helicopter Engines (anciennement Turbomeca) et le Laboratoire de Mécanique des Contacts et des Structures (LaMCoS) de l’INSA de Lyon (UMR CNRS 5259). Les boîtes de transmission par engrenages des moteurs d’hélicoptères convoient la puissance mécanique du turbomoteur aux accessoires (pompes, démarreur) et au rotor. Leur conception dépend des nécessités des équipements embarqués, en particulier l’allègement pour réduire la consommation en carburant. Les engrenages haute vitesse de la transmission sont allégés grâce à des enlèvements de matière dans les corps sous la denture, les voiles-minces. Un modèle dynamique d’engrenages a été développé pendant ce projet de recherche. Son approche modulaire permet l’inclusion conjointe des sollicitations dues aux vibrations de l’engrenage et de la nouvelle flexibilité des voiles-minces. Il dérive d’un modèle à paramètres concentrés, comprenant des arbres en poutre, des paliers et carters sous forme de raideurs additionnelles et un élément d’engrenage rigide inclus par son nœud central. Hypothèse est faite que tous les contacts sont situés sur les lignes de contact du plan d’action. Ces lignes sont discrétisées selon des tranches-minces dans les dents et la déviation normale des cellules est recalculée à chaque pas de temps selon la déflexion de la denture. Le nouveau modèle remplace l’engrenage rigide par une modélisation EF du pignon et/ou de la roue condensée sur les nœuds de jante. Une interface lie les raideurs du plan d’action discrétisé aux éléments finis du corps d’engrenage. L’élément prend donc en compte à la fois les sollicitations de l’engrenage et le comportement statique et modal des corps flexibles en dynamique. Des comparaisons sont faites avec des données numériques et expérimentales. Elles attestent de la capacité du nouveau modèle à prédire le comportement dynamique des engrenages flexibles à hauts régimes de rotation. Ces résultats intègrent entre autres des données locales et globales en dynamique. Finalement, le modèle est utilisé sur les deux cas académiques validés pour visualiser les effets des corps flexibles plus en détails. Un premier focus sera fait sur la déflexion statique due aux charges d’engrènement et sur l’optimisation sur le fonctionnement dynamique possible. Puis, les impacts des sollicitations de l’engrènement sur le voile en rotation seront étudiés. Enfin, le pignon et la roue seront affinés, afin de visualiser l’optimisation massique possible et son impact sur la dynamique de l’engrenage. / The research work presented in this manuscript was conducted in the Contact and Structural Mechanics Laboratory (LaMCoS) at INSA Lyon, in partnership with Safran Helicopter Engines (formerly-Turbomeca). In helicopters, the power from the turboshaft is transmitted to the rotor and the various accessories (pumps, starters etc…) via transmission gearboxes. In the context of high-speed, light-weight aeronautical applications, mechanical parts such as gears have to meet somehow contradictory design requirements in terms of reliability and mass reduction thus justifying precise dynamic simulations. The present work focuses on the definition of modular gear dynamic models, capable of integrating both the local phenomena associated with the instant contact conditions between the tooth flanks and the more global aspects related to shafts, bearings and particularly the contributions of light thin-rimmed /-webbed gear bodies. The proposed models rely on combinations of condensed sub-structures, lumped parameter and beam elements to simulate a pinion-gear pair, shafts, bearings and housing. Mesh elasticity is time-varying, possibly non-linear and is accounted for by Winkler foundations derived from a classic thin-slice model. The contact lines in the base plane are therefore discretised into elemental segments which are all attributed a mesh stiffness function and a normal deviation which are updated depending on the pinion and gear angular positions. The main originality in this PhD consists in inserting condensed finite elements models to simulate flexible gear bodies while keeping the simple and faster rigid-body approach for solid gears. To this end, a specific interface has been developed to connect the discretised tooth contact lines to the continuous finite element gear body models and avoid numerical spikes in the tooth load distributions for example. A number of comparisons with numerical and experimental results show that the proposed modelling is sound and can capture most of the quasi-static and dynamic behaviour of single stage reduction units with thin-webbed gears and/or pinions. The model is then applied to the analysis of academic and industrial gears with the objective of analysing the contributions of thin, flexible bodies. Results are presented which highlight the role of centrifugal effects and tooth shape modifications at high speeds. Finally, the possibility to further improve gear web design with regard to mass reduction is investigated and commented upon.

Made available in DSpace on 2016-12-23T14:21:18Z (GMT). No. of bitstreams: 1 Andre Manhaes Machado.pdf: 1039285 bytes, checksum: 2b356c4d0279c975232bd92c5e2ab326 (MD5) Previous issue date: 2013-11-16 / O petróleo é a principal fonte energética do mundo contemporâneo, insumo básico de diversos setores econômicos. Com a descoberta do Pré-sal, o Brasil tem a oportunidade de tornar-se um dos maiores produtores de petróleo. Entretanto, para que isso seja alcançado, vários desafios deverão ser superados e, dentre eles, encontra-se o problema de transporte de empregados para operarem as plataformas offshore, distantes até 300km de distância da costa brasileira. Os problemas referentes ao deslocamento de empregados por meio de helicópteros são usualmente tratados como o Capacitated Helicopter Routing Problem (CHRP). Com base nas restrições de origem e de destino de cada cliente, no número de veículos e na capacidade e restrições de voo dos helicópteros, neste tipo de problema deseja-se minimizar os custos de aluguel de helicópteros mais o custo total de quilômetros voados. A presente dissertação propõe um modelo de Programação Linear Inteira Mista (PLIM) para o problema de roteirização de helicópteros com base no Dial-a-Ride Problem (DARP). Além do modelo apresentado, foram apresentados duas abordagens para a execução do modelo de forma exata: i) abordagem sem agrupamento, na qual as requisições que possuem origens iguais e destinos iguais são modeladas como requisições distintas e ii) abordagem com agrupamento, na qual requisições que possuem origens iguais e destinos iguais são aglutinados numa nova e única requisição. O modelo matemático foi executado no software CPLEX e os resultados mostraram que instâncias com até 25 requisições podem ser resolvidas pela abordagem com agrupamento / Oil is the main energy source of contemporary world; it is basic inputs of various economic sectors. With the discovery of Brazil pre-salt, there is an opportunity to become one of the largest oil producers. However, to achieve her own goals, Brazil must overcome several challenges, including the problem of transporting employees to operate offshore platforms 300km distant away from the Brazilian coast. Problems related to displacement of employees by helicopters are usually treated as Capacitated Helicopter Routing Problem (CHRP). Based on source and destination restrictions of each client, the number of vehicles, capacity and helicopter flight constraints, this type of problem proposes to minimize the cost of renting helicopters and the total cost of flown kilometers. This dissertation proposes a model of Mixed Integer Linear Programming (MILP) for the helicopters routing problem based on a Dial-a-Ride Problem (DARP). Besides the presented model, we presented two approaches to implementing the model in an exact way: i) non-clustered approach, in which requests that have the same origin and destination are equal modeled as separate requests; and ii) clustered approach, in which requests that have the same origins and destinations are clumped together in a new single request. The mathematical model was implemented in software CPLEX and results showed that instances with up to 25 requests can be resolved in the clustered approach

Thesis (M.S.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Oct. 14, 2003). Thesis advisor: Ralph Kimberlin. Document formatted into pages (x, 64 p. : ill. (some col.), col. maps). Vita. Includes bibliographical references (p. 58-63).

No description available.

Regime recognition is an important tool used in creation of usage spectra and fatigue loads analysis. While a variety of regime recognition algorithms have been developed and deployed to date, verification and validation (V&V) of such algorithms is still a labor intensive process that is largely subjective. The current V&V process for regime recognition codes involves a comparison of scripted flight test data to regime recognition algorithm outputs. This is problematic because scripted flight test data is expensive to obtain, may not accurately match the maneuver script, and is often used to train the regime recognition algorithms and thus is not appropriate for V&V purposes. In this paper, a simulation-based virtual pilot algorithm is proposed as an alternative to physical testing for generating V&V flight test data. A “virtual pilot” is an algorithm that replicates a human’s piloting and guidance role in simulation by translating high level maneuver instructions into parameterized control laws. Each maneuver regime is associated with a feedback control law, and a control architecture is defined which provides for seamless transitions between maneuvers and allows for execution of an arbitrary maneuver script in simulation. The proposed algorithm does not require training data, iterative learning, or optimization, but rather utilizes a tuned model and feedback control laws defined for each maneuver. As a result, synthetic HUMS data may be generated and used in a highly automated regime recognition V&V process. In this thesis, the virtual pilot algorithm is formulated and the component feedback control laws and maneuver transition schemes are defined. Example synthetic HUMS data is generated using a simulation model of the SH-60B, and virtual pilot fidelity is demonstrated through both conformance to the ADS-33 standards for selected Mission Task Elements and comparison to actual HUMS data.