1,721,049 research outputs found
Application of the extra-modes method to the aeroelastic analysis of morphing wing structures
No full textWhen dealing with the design of morphing wings, conventional structural arrangements are commonly replaced by innovative solutions enabling shape changes through actively controlled elasticity or mechanical systems. In both cases, no simplified rules coming from consolidated experiences may be invoked to guarantee that a specific design will be characterized by stable and sustainable aeroelastic response to external loads expected in service.A rational approach for the aeroelastic analysis of the structural arrangements is therefore recommended since the earliest design stage so that the maturation of unflyable solutions is naturally avoided.The extra-modes method is herein detailed as a dramatically efficient tool to accomplish this paramount task. The morphing device is treated as a substructure and the aircraft (A/C) as the basic system on which the device is installed. Substructure's contribute to the aeroelastic response of the global system is expressed in terms of generalized parameters pertinent to additional and strategically defined modes capturing the substructure dynamics. After recalling the general formulation of the method, two case studies are presented in order to show its great potential to rapidly appreciate the aeroelastic behavior of a given design, irrespective of the maturity level of the design itself
Active metal structures
No full textMorphing of metallic wing structures has fascinated generations of researchers; numerous and sometimes bizarre architectures have been proposed, tailored to specific end-applications and aircraft type. Although different for layout, all of them can be categorized in two basic groups: mechanized architectures and compliant mechanisms.Mechanized architectures implement morphing through the rigid-body motion of stiff subcomponents interconnected by suitably designed kinematic chains and actuation leverages.Each subcomponent of the kinematic chain is sized to provide its own contribution to the adsorption of the external solicitations arising in operative conditions; actuators and actuation transmission line are sized to enable the motion of the system and to preserve given shape configurations while counteracting aerodynamic loads with the minimum need of power.Compliant mechanisms involve the deformation of structural elements to enable the required shape-change; mechanical properties of the structure have to be properly distributed in order to assure adequate morphing compliance and adequate stiffness to withstand external loads.In this chapter, the design philosophy behind each type of morphing structure has been presented, together with practical applications to wing trailing edge camber adaptation.By referring to similar end-application, the adopted design strategies and obtained outcomes are compared, thus better highlighting the advantages and weak points of each morphing solutio
Morphing wing flaps for large civil aircraft: Evolution of a smart technology across the Clean Sky program
No full textMorphing wing structures are widely considered among the most promising technologies for the improvement of aerodynamic performances in large civil aircraft. The controlled adaptation of the wing shape to external operative conditions naturally enables the maximization of aircraft aerodynamic efficiency, with positive fallouts on the amount of fuel burned and pollutant emissions. The benefits brought by morphing wings at aircraft level are accompanied by the criticalities of the enabling technologies, mainly involving weight penalties, overconsumption of electrical power, and safety issues. The attempt to solve such criticalities passes through the development of novel design approaches, ensuring the consolidation of reliable structural solutions that are adequately mature for certification and in-flight operations. In this work, the development phases of a multimodal camber morphing wing flap, tailored for large civil aircraft applications, are outlined with specific reference to the activities addressed by the author in the framework of the Clean Sky program. The flap is morphed according to target shapes depending on aircraft flight conditions and defined to enhance high-lift performances during takeoff and landing, as well as wing aerodynamic efficiency during cruise. An innovative system based on finger-like robotic ribs driven by electromechanical actuators is proposed as morphing-enabling technology; the maturation process of the device is then traced from the proof of concept to the consolidation of a true-scale demonstrator for pre-flight ground validation tests. A step-by-step approach involving the design and testing of intermediate demonstrators is then carried out to show the compliance of the adaptive system with industrial standards and safety requirements. The technical issues encountered during the development of each intermediate demonstrator are critically analyzed, and justifications are provided for all the adopted engineering solutions. Finally, the layout of the true-scale demonstrator is presented, with emphasis on the architectural strengths, enabling the forthcoming validation in real operative conditions
Integrated design approaches for an innovative multifunctional flap architecture based on distributed electromechanical actuation
No full textAn innovative adaptive architecture was defined for the wing flap of a large civil transport aircraft with the scope of improving high-lift performances and wing efficiency in cruise. The adaptation of the flap shape follows three different morphing modes and is ensured by a smart robotic structure driven by electric actuators combined with powerful transmission lines. For robotic morphing architectures, the design of the actuation system needs to be carried out in combination with the supporting structure as they both participate in withstanding the operative loads. The integrated approaches adopted for the design of the morphing flap structure and embedded actuation have been outlined in this work; the outcomes of each design phase have been presented and critically analyzed
On the experimental characterization of morphing structures
No full textA major difficulty in the design of morphing devices for aircraft wings is to reach an adequate compromise between high load-carrying capacity to withstand aerodynamic loads and sufficient flexibility to achieve better aerodynamic performance. Such counteracting and demanding targets lead to an increased structural complexity whose experimental characterization is a matter of high priority prior to the ultimate physical integration into the aircraft structure. Compared to the passive counterpart, morphing devices enable augmented capabilities by locally adapting wing shape and lift distribution through either a quasistatic or dynamic deflection, with excursions ranging into a few units of degrees, positive and negative.This chapter provides an overview of the verification approaches suitable for morphing devices ranging from the basic concepts applicable to individual subsystems up to the global experimental analysis of the integrated system. A number of test objectives are illustrated at both component and system level, providing practical tips for the experimental analysis of morphing structures combining both compliant structural systems and multibox self-contained actuation mechanisms
A Practical Approach for the Mitigation of Seismic-Induced Vibrations in Slender Metallic Structures through Magnetorheological Fluid Dampers
No full textThe mitigation of seismic-induced vibrations is essential for the effective protection of buildings and occupants during earthquakes. This especially applies to slender buildings with metallic frames; in this case, the structure’s geometrical layout and relatively low damping properties favor an excessive and potentially catastrophic oscillatory response to a seismic event. Semiactive systems for energy dissipation are among the most commonly used strategies to control this oscillatory response. They offer the right balance between the reliability of passive devices and the versatility and adaptability of fully active systems. In this work, a vibration-suppression system based on dissipative bracings that integrate commercial magnetorheological fluid dampers (MRDs) was designed and validated through experimental tests on a true-scale structural model that was representative of a five-story slender building with a metallic frame. A practical and robust approach was proposed for: (1) The definition of the MRD type in compliance with a predefined mitigation target for seismic-induced accelerations on each floor of the structure; (2) The modeling of the MRDs, contribute to the dynamic response of the structural system. The approach involves a linearized formulation of the characteristic damping curves of the MRDs at different values of the activating current. By relying upon this linearization, a rapidly converging iterative process was set up to simulate the seismic response of the structure in the case of activated or deactivated dampers. The reference structure and the vibration-suppression system were then manufactured and tested on a sliding table, which provided realistic seismic excitation. The good correlation levels between the numerical predictions and the experimental measurements proved the effectiveness of the conceived system and of the approaches that were used for its design and simulation
A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear
No full textOleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data
ROTATIONAL MOTION OF A HOMOLOGOUS SERIES OF SOLVENT MOLECULES IN AMORPHOUS POLY(METHYL METHACRYLATE) .1. STUDIES OF THE SOLVENTS
No full textSARISTU: Adaptive Trailing Edge Device (ATED) design process review
No full textSARISTU was a big cooperation project granted by the European Commission, 7th Framework Programme, carried out between 2011 and 2015. It dealt with smart aeronautic structures, both morphing and sensored; its main target was to demonstrate the feasibility of designing, manufacturing and operating in representative environment, instrumented structures. Till now, it represents the major effort carried out within the European Union on the development of adaptive architectures for air systems. Inside that big activity, the realization of an Adaptive Trailing Edge Device (ATED) for wing camber adaptations aimed at compensating the weight reduction following the fuel consumption during cruise was addressed. It made the core of investigations target variable geometry aircraft components together with two other analyses concerning the development of shape-changing winglet and droop nose. ATED activities were conducted by the Italian Aerospace Research Centre (CIRA) in tight cooperation with the University of Napoli, “Federico II”, who coordinated a group of 12 different partners from 8 different nations (France, Germany, Greece, the Netherlands, Israel, Spain, Turkey, and Italy). In this paper, an integral synthesis of that work is reported, with a focus on the definition and realization of the components of the presented device. The publication is in fact meant as the first part of a series that is aimed at overviewing the whole adaptive trailing edge development, till wind tunnel tests execution. Such a concise report is a critical and harmonized review of what have been performed by many colleagues spread all over Europe, all of which are duly recalled in the reported bibliography where the reader may access more detailed information and descriptions. In detail, the paper starts with a general introduction of the concept and its aims, to move to the specs definition immediately after. Then, it deals with a short but comprehensive description of the main ATED components: structural skeleton, skin, actuation and sensing systems. It is worth remarking that the paragraph dedicated to the body frame includes some discussion about aeroelastic assessment and manufacture, seen as complementation for a complete assessment of the design constraints
- …
