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Preface of the "symposium on progressing multidisciplinary design analysis and optimization"
No full textA super-convergent thin-walled 3D beam element for analysis of laminated composite structures with arbitrary cross-section
No full textAn efficient, fully coupled beam model is developed to analyse laminated composite thin-walled structures with arbitrary cross-sections. The Euler–Lagrangian equations are derived from the kinematic relationships for a One-Dimensional (1D) beam representing Three-Dimensional (3D) deformations that take into account the cross-sectional stiffness of the composite structure. The formulation of the cross-sectional stiffness includes all the deformation effects and related elastic couplings. To circumvent the problem of shear locking, exact solutions to the approximating Partial Differential Equations (PDEs) are obtained symbolically instead of by numerical integration. The developed locking-free composite beam element results in an exact stiffness matrix and has super-convergent characteristics. The beam model is tested for different types of layup, and the results are validated by comparison with experimental results from literature
Ornicopter Multidisciplinary Analyses and Conceptual Design
No full textThe tail rotor of conventional helicopters has always been considered a necessary 'evil'. It is necessary to counteract the reaction torque of the engine and to control the helicopter in yaw but it consumes substantial power, has only marginal control authority under unfavourable wind conditions, and it is noisy, vulnerable and dangerous. A solution to all these problems would be a helicopter concept that eliminates the need for a tail rotor. The so-called 'Ornicopter', a helicopter with flapping blades, is such a concept. The mechanism of the Ornicopter is inspired by bird flight. When birds flap their wings they are able to generate both a lifting force and a propelling force from this single movement. Instead of propelling a helicopter blade by spinning it around and deriving lift from this rotating movement, as is done in conventional helicopter configurations, the Ornicopter flaps its blades like a bird and derives both lift and a propulsive force from this movement. In this case the blades propel themselves and there is no longer a need for a direct torque supplied by the engine to rotate the blades. The Ornicopter's rotor, therefore, will not cause a reaction torque on the fuselage, which makes the tail rotor's anti-torque function redundant. The goal of the present thesis is to develop a thorough understanding of the Ornicopter concept and its feasibility throughout a realistic flight envelope. The first part presents the analysis of the Ornicopter's main characteristics regarding performance, stability, controllability, handling qualities, as well as an exploratory vibratory analysis. In the second part a preliminary design and sizing thereof are presented based on the conclusions obtained in the first part. The basis for the Ornicopter's study is an analytically-derived flight mechanics model. The model is based on the blade element theory (BET) and considers 6 rigid body degrees of freedom (DoF), 3 DoF blade flapping dynamics and 3 DoF Pitt-Peters inflow dynamics. Previous mathematical models developed as a proof of the Ornicopter concept have concentrated mainly on hovering flight. The model developed in this thesis is capable of representing the Ornicopter's dynamics well within its entire operational flight envelope. As a benchmark for the Ornicopter's specifications, the Bolkow Bo-105 helicopter is used. The Bo-105 helicopter is a light twin-engine, multi-purpose helicopter developed in Germany in the 1970s. For the initial values of the design parameters of the Ornicopter (such as rotor radius, blade loading, rotor tip velocity, vertical fin size) the Bo-105 helicopter design is used. A 2X2 anti-symmetric rotor flapping configuration (with two opposite blades flapping in the same direction) is used for the Ornicopter in order to eliminate the necessity for a tail rotor. Using these design parameters it is demonstrated that the Ornicopter rotor can generate enough propulsive torque to rotate the blades with modest flapping amplitudes (maximum less than 9 deg). The present thesis demonstrates that, compared to the Bo-105 helicopter, the Ornicopter concept suffers from higher required power, a smaller flight envelope (mainly due to the larger rotor stall area) and lower yaw stability. All these drawbacks are attributed to the large rotor blade angle of attack variation introduced by the forced flapping mechanism and the absence of a tail rotor. In the second part of this thesis, the Ornicopter concept is optimized for performance. Keeping the performance specifications of the Bo-105 as the objectives, the design values (blade radius, blade loading etc) are turned to fit the Ornicopter concept and no longer use the Bo-105 design values. The design optimization is formulated through minimization of the required power, while satisfying the stall area requirement. The thesis proves that the optimal design for the Ornicopter as compared to the Bo-105 benchmark is characterized by a lower blade loading, increased rotor tip velocity and larger vertical fin size. This optimal design results in an enlarged flight envelope due to the reduced rotor stall area and improved yaw stability in forward flight. Nevertheless, despite these improvements in the Ornicopter's flight envelope, there is a slight increase in required power when compared with the Bo-105 specification (approximately 5% at 150 knots). To compensate for the higher profile power needed for the Ornicopter's optimal design, a larger rotor radius is required in order to reduce the induced power and keep the increase in the total required power to a minimum. This thesis may be considered as a first step in rationalizing the expectations regarding the Ornicopter's tailless helicopter design. The thesis proved that this new concept shows a slightly poorer performance than that of conventional helicopters regarding power consumption in forward flight and service ceiling. This is disappointing since one of the assumptions was that the elimination of the tail rotor would also eliminate the power consumption associated with a tail rotor. Further analyses of the Ornicopter's performance (such as endurance, payloads, climbing performance, and environmental performance related to safety and noise), costs or maintenance should be performed for a comprehensive understanding of the advantages and disadvantages of this helicopter concept.Aerospace Design, Integration & OperationsAerospace Engineerin
Sequential Multi-Disciplinary Optimization for the Conceptual Design of a Blended-Wing-Body Aircraft
No full textConcurrent stringer topology and skin steered fiber pattern optimization for grid stiffened composite shell structures
No full textFlying GLARE
No full textAt the end of the second millennium did the aircraft industry decide for the first time to apply the fiber metal laminate GLARE in a large quantity on a civil transport aircraft. It was focused on an application of the material on the pressurised fuselage, the decision driven by the demand for weight saving at an affordable cost level. GLARE material properties are linked to both, monolithic aluminium properties as well as fiber composite properties, with the preference depending on the particular strength feature under investigation. Between others, three major structural mechanic advantages compared with monolithic aluminium can be identified for fiber metal laminates, i.e. the lower density, the crack bridging capability of the fibers in presence of a fatigue crack in the particular aluminium sheets and the possibility to tailor the material according to structural mechanic requirements by appropriate orientation of the fibers. Essential for an economic application of the material is the acceptance of 'flying with undetectable fatigue damages'. This rule and it's implications on structural sizing and justification is discussed in depth in this report, leading to the particular subject of the strength behaviour of riveted joints in a fatigued condition. Because GLARE contains an epoxy resin prone to moisture absorption, strength degradations due to environmental influences have to be taken into account. However, as for other materials, it is searched for a realistic exposure in order to design a structural component to the limits of the material strength and to avoid unnecessary high reserves. An outdoor exposure program is under evaluation as part of the structural investigation, which extends the time frame of this thesis. Structural components are supposed to remain for up to 6 years on a tropical exposure site. However, evaluated weight gain measurements allow extrapolations for 30 years aircraft operation and the definition of a representative accelerating ageing process. Extensive results on particular GLARE related investigations are reported since the end of the 1980's. This thesis is compiling the available information on fatigue issues and environmental related material issues, it is extending the previous research and it interprets the material properties within the framework of the mandatory airworthiness rules. For that purpose, two structural items which are tested by Airbus under full scale conditions are investigated concerning all particular strength properties which are required for certification or not are investigated. The application of airworthiness regulations which are defined for monolithic aluminium are discussed for GLARE in chapter 1. While fatigue sensitive monolithic aluminium structures have a relatively long crack initiation life but a relatively short crack propagation life, GLARE shows the opposite behaviour. What does that mean for the certification of a GLARE structure? Which fatigue methods should be used for the certification and is GLARE a single load path or a multiple load path structure? Some basic rules are discussed and proposals concerning the structural certification are provided. No type certification of a commercial passenger aircraft is accepted without test substantiation. The test pyramid is starting with elementary specimens (can be tested early in a project) and finishes with a full scale fatigue test. Chapter 2 discusses the particular influences which have to be considered for structural certification, e.g. crack initiation scatter and temperature sensitivities to crack initiation, and which have to be reconsidered for GLARE. Chapter 3 presents all specimen types which belong to the outdoor exposure program, i.e. test series from which some specimens are shipped to a tropic exposure site and some are tested under laboratory conditions, for comparison. The relevance of the particular specimen types and their history for GLARE is briefly discussed. A review of accelerating ageing experiences of previous researches with Fiber Metal Laminates is done in chapter 4. Diffusion coefficients for GLARE3 made of 2024T3/FM94 are determined. First weight gain measurements which are available from the outdoor exposure test site are investigated and interpreted in chapter 5. Predictions of the weight gain of GLARE around bore holes for both, long range aircraft and short range aircraft, are performed. Chapter 6 presents elementary specimen test results for the two tested materials, related to different ageing conditions. First experiments with specimens which have been exposed for one year outdoors are included. The crack initiation and crack propagation scatter for a row of bore holes is determined. Chapter 7 is dealing with coupon specimens, which are representative for the full scale structure tested by Airbus. A review and calibration of crack initiation, crack propagation and residual strength methods under development by Airbus Deutschland and Delft University is performed for a prediction of the full scale behaviour. The calculated results are discussed in view of a fatigue & damage tolerance certification. Full scale test results are related to the elementary- and the coupon experiments performed in this thesis. The outdoor exposure investigation is extended by a few panel tests, i.e. non-stiffened riveted repair panels, non-stiffened bonded repair panels and door corner cut out specimens. This analyses are collected in chapters 9 to 11. All experiments and analysis are performed with/for GLARE composed of aluminium 2024T3 and prepreg FM94/S-glass, cured at 120°C. Due to the wide range of specimen types each of them couldn'd be provided in a high quantity, for economic reasons. Therefore just property trends can be provided. The investigations performed in frame of this thesis contribute to the verification of the TU Delft / Airbus computer program 'FML F&DT Toolbox', which is developed at the same time.Aerospace Engineerin
Structured Design Automation
Full text linkOrganised by: Cranfield UniversityThe next stage in product development process evolution should be the automation of labour intensive
repetitive steps. The design automation strategy should follow the trend of the supply chain management
approach and deliver a flexible framework, allowing local specification and adjustment The proposed
Adjoined Design Automation Process Trajectory (ADAPT) and associated tools provide such a framework. It
covers the process from fuzzy front-end to the evaluation of automated processes. Considerable lead time
and cost savings are shown for electrical component design and the feasibility of a Domain Specific
Language approach is an important step towards acceptance of design automation.Mori Seiki – The Machine Tool Compan
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