1,720,981 research outputs found
PRELIMINARY ASSESSMENT OF A WARPING WING CONFIGURATION IN ROLLING CONTROL
No full textThe preliminary analysis and the possible advantages of a morphing solution replacing the traditional hinged aileron configuration has been analyzed in order to evaluate its energy efficiency in UAV configurations with limited payload capacity and power available for flight. The parameters considered are the wing aspect ratio, the torsional stiffness, the position and the aileron deflection and the consequent actuation rib rotation in the morphing solution. The analysis showed that the morphing solution is very advantageous in all cases requiring high rolling moments with a more evident advantage at high aspect ratios. The traditional solution still remain advantageous at low aspect ratios and low rolling moments
Progetto S55 Replica
No full textIl Savoia Marchetti S55 è un idrovolante simbolo dei notevoli progressi tecnologici dell’Italia in campo aeronautico durante gli anni ’20 e ’30 e reso famoso da una serie di voli a lunga percorrenza da record. Nonostante la produzione toccò i 250 esemplari ad oggi non esiste nessun esemplare volante e solo uno di essi si è conservato fino ai giorni nostri ed è attualmente esposto nel museo aeronautico TAM in Brasile. Nel 2015 un gruppo di professionisti e appassionati del settore aeronautico ha avviato il progetto Replica55 coordinato dal comandante Francesco Rizzi, con l'obiettivo di progettare, costruire e far volare una replica del velivolo S55 (www.replica55.it). The Savoia Marchetti S55 is a seaplane symbol of the remarkable aeronautical know how reached in Italy in during the '20s and' 30s, and confirmed by a series of record long-range flights. Although were made about 250 aircraft, to date does not exists one flying airplane. Currently the only one remaining and preserved is exhibited in the TAM aeronautical museum in Brazil. In 2015 a group of competent and enthusiastic professionals of the aeronautics sector started the "Replica55 project" coordinated by the commander Francesco Rizzi, with the aim of designing, building and flying a replica of the S55 aircraft. (www.replica55.it)
EQUIVALENT MATERIAL IDENTIFICATION IN COMPOSITE SCALED HULLS VERTICAL IMPACT TESTS
No full textAirworthiness regulations require that aircraft should be proved to ensure the survivability of the ditching for the passengers. In particular seaplane aircrafts must be designed for water loads developed during take-off and landing with the seaplane in any attitude likely to occur in normal operation at appropriate forward and sinking velocities under the most severe sea conditions [1]. In order to make a stress analysis of seaplane floats, and especially of the members connecting the floats with the fuselage, it is of great importance to determine the maximum pressure acting on the floats during landing [1,2,6]. The impact in water is a very complicated phenomenon due to the interaction between the hydrodynamic field and the structures so the possibility to investigate its characteristics by means of a scaled model seems straightforward. In general the similarity procedure requires the scaling of different properties (mass, length, speed, etc.) in order to properly represent such a phenomenon. In the present case the fluid-dynamic phenomena are scaled thanks to the Froude similarity while the definition of specific material and its scaling rules for a complete similarity is required in several cases particularly when composites play a predominant role on the test response. The introduction of TRACE parameter is proposed as a method orienting the designer for the right material selection in these situations [2,3,4,5]. Non-dimensional TRACE behaviour in function of shear-ratio coefficient is shown in figure 1a. Materials can be grouped in classes according to the value of the orthotropic ratio and each class can be scaled by TRACE. Non-dimensional deflection is determined as a function of load parameters and TRACE according to typical material classes definition. The procedure is extended to a typical drop-test impacted on water including structural flexibility [7,8]. Numerical simulation using the LS-DYNA software is used to validate the procedure in predicting the maximum pressure in the first phases of impact (figure 1b and figure 2b). The model shown in figure1b provides the adoption of SPHs, a particular tool adopted for the modelling of a fluid like water. Each SPH (Smoothed Particle Hydrodynamics) is described like a structural FEM node and by a EOS (Equation of State) that describes the mechanical behaviour and interaction with other SPH and the structure. LS-DYNA is an explicit software, so it can simulate dynamic phenomena.
An experimental test is finally designed as shown in figure 2a to calibrate the physical and numerical parameters useful for the definition of SPH properties with the aim to define analyse and correctly describe the dynamics of fluid-structure interaction during a seaplane hull water impact (figure 2b)
Environmental friendly inter-city aircraft (ENFICA-FC) and preliminary analysis for 2-seat aircraft conversion into fuel cells powered innovative system
No full textThe main objective of the ENFICA-FC project (ENvironmentally Friendly Inter City Aircraft powered by Fuel Cells), funded by European Commission, is to develop and validate the use of a fuel cell based power system for propulsion of more/all electric aircraft. The following items shall be pursued: a) A fuel cell system shall be designed, built and tested in laboratory ready to be installed on board for flying; b) A high efficiency brushless electric motors and power electronics apparatus for their control shall be designed and manufactured ready to be installed on board for flying; c) high efficiency would be obtained by an optimised aerodynamic propeller design; d) A study of the flight mechanics of the new aircraft will be carried to verify the new flight performance; e) Validation of the overall high performance of an all electric aircraft by means of flight test. The fuel cell system will be installed in a light sport aircraft which will be flight and performance tested as a proof of functionality and future applicability for inter city aircraft. A selection of most suitable aircraft for conversion is presented and the light sport aircraft Rapid 200 chosen. The high efficiency two-seat existing aircraft Rapid 200, manufactured by Jihlavan Aircraft, has been selected over more than 100 light sport aircrafts after the preliminary reported evaluation based on merit index as indicated. The aircraft will be used for the conversion from internal combustion engine to an electric one. Analysis about the COTS equipments for electric propulsion system has been performed and presented. Design indication of an optimal propeller complete the identification phase that continue with the analysis of some parameters influencing the general configuration of the converted aircraft and the mission items. Preliminary consideration about the definition of storage configuration are presented and some safety issues are considered for H2-gas management. Design indications and conversion limitations conclude the reported activity
NUMERICAL AND EXPERIMENTAL VALIDATION OF UNITIZED BEAM MODEL
No full textThis paper presents the numerical and experimental validation of a variable stiffness box beam
model made by an arrangement of stiffened and unstiffened panels. The derivation of the equivalent
properties of curvilinear stiffened plates is briefly summarized. The validity of the equivalent
continuum plate model is assessed. The governing equations of the variable stiffness boxbeam
are presented. Once the model is established, the stiffeners’ path to attain a desired
static performance is sought. The optimal configuration is determined by a topology optimization
problem where the design variables become the orientation of the curved stiffeners at prescribed
points. Several analytical examples along with one experiment are presented to show the validity
of the model presented herein
Numerical simulation and experimental validation of slender wings flutter behaviour
Full text linkThe flutter instability of high aspect ratio wings is numerically investigated by means of finite element aeroelastic analysis.
The effect of static equilibrium deflection as well as the additional differential stiffness was introduced in the calculation
by a new procedure based on MSC NastranTM commercial code. The difference between the classic linear flutter
calculation and the new procedure presented has been demonstrated numerically and also experimentally. The main
parameters that influence the aeroelastic phenomenon were also highlighted and used to define the aeroelastic similarity
model related to a typical aircraft of the high altitude long endurance aircraft category
Numerical and experimental structural characterization of composite advanced joint for ultra light aerospace platforms
No full textIn the present work, the results of a numerical campaign aimed to evaluate the progressive damage failure
analysis (PDFA) of a specific advanced pin-hole connection under tensile and compressive loads are presented.
The proposed numerical models are based on the application of constitutive material models available in LSDYNA. High fidelity shell-cohesive method was employed to represent composite delamination behavior. In this
model each lamina has been modeled separately with the application of interlaminar cohesive elements.
Preliminary experimental/numerical correlation indicates that the selected modeling technique predicts
experimental results when compared to the proposed laboratory test results. A reduced computational cost has
been also determined. The location and extension of the predicted fracture during the damage process are
comparable to experimental observations. The proposed methodology demonstrates its preliminary ability to be
used for design of composite joints up to failure. Specific outcomes have been also pointed out
Coupled thermo-mechanical numerical modelling of carbon fibre reinforced composites impacted with different projectile configurations
Full text linkA key challenge in building a predictive numerical model for composite structures is the ability to accurately characterize their failure behaviour, especially under impact loading. In this paper, a coupled thermo-mechanical modelling technique and the associated numerical simulations of carbon fibre-reinforced composite panels under the high-velocity impact (HVI) are introduced. The modelling technique aims to evaluate the progressive damage failure analysis (PDFA) of a flat composite panel made of T800/F3900 unidirectional carbon fibre and epoxy, with 16-ply in a quasi-isotropic layup configuration [(0/90/45/-45)2]S. Mechanical characterization test data of the proposed composite materials have been obtained from FAA experimental campaign. High fidelity complete stacked shell-cohesive method is implemented to evaluate composite delaminations and intralaminar damage. The heat generated due to the projectile kinetic energy and impact-induced damage energy transformation is investigated with the proposed numerical coupled model. Thermal effects on the mechanical performance of composite targets are investigated based on the application of the constitutive transient thermal coupling method available in LS-DYNA®. Moreover, the explicit dynamic finite element analysis presented considers four characteristic aerospace projectiles to compare the development of the damage generated during normal highvelocity impact events. The impact response results of the selected projectile configurations, including rubber cylindrical projectile, bird-like projectile, CFRP composite platelike projectile, and ASTM D8101 aluminium axisymmetric projectile, are compared. Impactors with equivalent kinematic energy are investigated with emphasis on energy transfer mechanisms and the local projectile-induced target deformation, damage, and failure. The study introduces the proposed modelling techniques, energy transfer phenomenon, and damage mechanisms that are observed in the target plates. The proposed numerical technique will be used in future research works to investigate engine bird-strike events and the consequently Fan Blade-Out (FBO) scenario to increase the reliability of aerospace structures and to improve the design numerical methods
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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