1,721,016 research outputs found
Simulation and experimental validation of fatigue endurance limit of copper alloy for industrial application
No full textFatigue resistance performance represents one of the main characteristic for flexible structures as those used in aerospace and other means of transport. For this reason, particular attentions are dedicated during the design stage to the evaluation of the lifetime resistance parameters. Many numerical and analytical approaches are actually available for this purpose, as well-standardized experimental test procedures have been assessed. With reference to a copper bar of an electric motor, the paper presents a survey of the main analytical and numerical methodologies for the prediction of the fatigue peculiarities. The estimation data have been than validated by an experimental campaign in simulated operating conditions, revealing advantage and drawbacks of different models
Experimental Characterization of Innovative Viscoelastic Foams
Full text linkThe evolutionary trend in the automotive industry has produced over time numerous performance and aesthetic innovations, however, the exponential development related to transportation technologies also introduced new requirements concerning the environmental impact [1]. The awareness of ecological issues has led to a reorganization of the evaluations and the vehicle design, currently aimed at reducing the problems that have emerged in empirical investigations and the parallel increase in environmental solutions. The vehicle renewal process involves targeted technical mutations both to observance of ecology as to the safety and comfort of the driver. New recyclable materials and more resistant have been developed in order to minimize the environmental impact of the vehicle even at the end of the operating life of its components, as well as solutions relating to the reduction of noise pollution generated as a response to the requirements of comfort. Modern research programs on a global scale have set themselves the objective of exploiting the potentiality of innovative technologies in the optimization of vehicles efficiency, the noise reduction and in the consequent reduction of fuel burn. One of the crucial topics in the greening of the new generation automotive sector is therefore the use and development of high vibro-acoustic performance materials. The goal of this research is properly focused on the analysis of viscoelastic materials appointed to increase the damping of the vibrations generated in a vehicle. The use of a viscoelastic material in this context is due to its high property to convert vibrational energy into heat, providing a significant dissipation of the vibrations. Trade-off analyses are performed in order define the stiffness and damping capacity of several viscoelastic foams with different thickness and density
Sound proofing and thermal properties of an innovative viscoelastic treatment for the turboprop aircraft fuselage
Full text linkLow-resilience polyurethane foams including several additive constituents were synthesized to improve their vibro-acoustic performances, as well as the thermal insulation. viscoelastic polymer additive can attenuate vibrations and absorb sound energy. the vibro-acoustic properties of two innovative viscoelastic treatments fabricated with polyurethane foams are discussed in this paper using a typical aeronautical panel test setup. Since an aircraft insulation arrangement must provide both noise and thermal insulation for the specified operating conditions and expected thermal comfort of passengers, the thermal conductivity of the samples has been examined assuming a testing range between 20 °C (room temperature) and − 40 °C (cruise altitude). the results highlighted an optimal behavior of the novel viscoelastic foams in terms of both acoustic and thermal performance, offering a very interesting self-embedded solution with a good weight to performance ratio, compared to standard blanket composed by extra viscoelastic treatments
Aero-servo-elastic design of a morphing wing trailing edge system for enhanced cruise performance
No full textThe Adaptive Trailing Edge Device (ATED) was a sub-project inside SARISTU (Smart Intelligent Aircraft Structures, 2011–2015), an L2 level project of the 7th EU Framework programme coordinated by Airbus, aimed at developing technologies for realizing a morphing wing for the improvement of general aircraft performance. That study, divided into design, manufacturing and testing phases, involved universities, research centers and leading industries of the European consortium. The aim of the present work is to predict the aero-servo-elastic impact of a full-scale morphing wing trailing edge on a CS-25 category aircraft. Within SARISTU, many FE models were realized, taking into account the complete and complex adaptive wing structure behavior. Those numerical representations referred to the 5.5 m wing section that was then employed for wind tunnel tests; such segment included the winglet and was representative of the outer wing segment (namely, the so-called “aileron region”). Those models were taken as reference to develop numerical representation of the considered wing that better suited the complete wing segment, from the fuselage attachment to the end of the flap region. Therefore, a scaling process was necessary, aimed at translating the former architectures to the new geometries. This kind of extrapolation had the advantage to take into account larger rooms to host the complex actuator system with all its components. MSC Nastran® FE models were elaborated to estimate stiffness and inertial distributions that allowed constructing the stick-beam mock-up of the complete structure. Several cases of flutter analysis were investigated by an in-house code, SANDY 3.0, to verify the safety requirements imposed by the applicable aviation regulations (paragraph 25.629, parts a and b-1). Moreover, dynamic stability assessment was performed with respect to single and combined failures of the actuation line and kinematic chain enabling morphing in order to support FHA (Fault and Hazard Analysis)
An innovative numerical approach for railway rolling noise forecast
No full textIn recent years there has been a growing worldwide development of rail transport, mainly due to technological innovations both on armaments and on rail vehicles. Such technological issue focused almost parallel on two main fronts: on one hand the performance enhancement and on the other side the internal comfort. This technology advancement has been driven mainly by the need to move goods and passengers over long distances in a short time, making it the safest transportation system in the world thanks also to the latest monitoring systems, of which European Community is undoubtedly one of the major leaders. The passenger transport has introduced problems related to comfort: traveling so fast is the main goal so long as it is comfortable and safe. One of the requirements that mostly turned out to be significant and sometimes more difficult to satisfy is that regarding acoustic comfort and environmental impact. As known, the regulations become with the passage of time more and more stringent, and every company that wants to operate in this area is required to respect them. The acoustic comfort improvement implies the intervention as much as possible focused on noise sources, which in this case are constituted by: electric motor, pantograph, wheel-rail contact. In such research framework, the authors focused on determination of a simple, but at the same time reliable, method for radiated sound power assessment in the wheel-rail contact due to combined wheel-rail roughness in order to reduce the environmental impact of this type of transmission system. Targeted analysis were implemented in an efficient numerical investigation in MSC NASTRAN® and ACTRAN® environments providing the necessary vibro-acoustic parameters as input data for the further definition of the wheel-rail interaction force by a MATLAB® customized tool, once known the roughness profile
Experimental and numerical assessment of innovative damping foams
No full textThe automotive industry is currently experiencing relevant technology changes in the design of the engines, transmission and total drivetrain, induced by increasing customer demand for fuel efficiency and more stringent government requirements in emissions and safety. One of the problems relating to environmental impact concerns the noise emitted by the vehicle, for which various solutions have been experimented: new and more resistant materials have been worked out in order to minimize noise pollution and the environmental impact of the vehicle, even at the end of the operating life of its components. This research illustrates a solution as a response to those requirements, as well as being a response to the targets of comfort: a viscoelastic material, appointed to increase the damping of structures involved in vibroacoustic phenomena generated in a vehicle. The performance of these innovative materials have been analyzed both from a numerical standpoint that experimental. Starting from the empirical results of tests carried out in the laboratory, finite element models have been developed in order to have a suitable numerical database for further vibro-acoustic simulations
Vibro-acoustic response of a turboprop cabin with innovative sidewall viscoelastic treatment
No full textIn recent years, it's considerably grown the market demand for increasingly performing and comfortable aircrafts as a new mandatory design target. Among the determining factors for the internal comfort, are included the noise and vibrations, the source of which is detected mainly in the propulsion unit especially in the case of turboprop category: the most significant component of the noise perceived inside a cabin is undoubtedly the blade-passage load exerted by the propeller. Recently were therefore tested techniques, both active and passive, of vibration emission reduction and sound absorption, however the goal remains to find solutions by extremely low-weight and easy to apply on the real mock-up. As known, a damping treatment is typically used to reduce noise coming from fuselage structure vibration under acoustic loading excitation. In such research context, the vibro-acoustic performance of the viscoelastic material for replacing the conventional interior blanket of the fuselage sidewall have been investigated for the well-known higher dissipation capacity and energy storage. Starting from experimental tests by means of different measurement techniques carried out on an innovative foam sample, the dynamic parameters were estimated according to identify suitably the material performance database for further finite element analysis on a turboprop fuselage model. The outcomes achieved have emphasized a significant role of the viscoelastic foam than the standard blanket with respect to the internal sound pressure levels abatement as well as the thermal insulation. The developed foam prototype is also easily integrable with an outer layer ensuring a fully removable embedded solution for the maintenance inspections
Design and testing of a prototype foam for lightweight technological applications
Full text linkOver recent years, in the automotive field, numerous performance and aesthetic innovations have been produced thanks to the development process of the manufacturing technologies gained mainly in the aerospace industrial context. The automotive industry is currently experiencing relevant technology changes in the design of the engines, transmission and total drivetrain, induced by increasing customer demand for fuel efficiency and more stringent government requirements in emissions and safety. One of the problems relating to environmental impact concerns the noise emitted by the vehicle, for which various solutions have been experimented: new and more resistant materials have been worked out in order to minimize noise pollution and the environmental impact of the vehicle, even at the end of the operating life of its components. Several research programs are currently running or recently terminated worldwide to explore the feasibility of smart materials. The increasingly dominant role of lightweight materials in many technological sectors is motivated by the multitude of benefits that they could offer like the weight optimization and the reduction of the fuel burn and noise levels. This research illustrates a solution as a response to those requirements, as well as being a response to the targets of comfort: a viscoelastic material, appointed to increase the damping of structures involved in vibro-acoustic phenomena generated in a vehicle. The performance of these innovative materials have been analyzed both from a numerical standpoint that experimental. Static mechanical properties and modal parameters carried out in the laboratory, pertinent to each configuration were arranged into a rational database for further studies on the vibro-acoustic behaviour of the coupled cavity-structure system. The main goal of this research project has been reached in the design, manufacturing and testing of an innovative viscoelastic prototype got out by the best compromise of structural and acoustic characteristics of pre-existing trim materials
Development of a dynamic tool for aircraft noise reproduction
Full text linkThe aircraft is surely one of the most considerable invention that changed the transport-engineering field, since flying was already an ancient dream come true just a few years ago. Now it is really easy to reach many far places even if most people have no clue how flying is possible. However, as factories do, these large and faster and faster machines return a consistent amount of pollution every day. During take-off, engines reach the highest RPMs returning the most noise possible, and during landing, mobile surfaces produce a lot of aerodynamic disturbs releasing energy in the air while landing gears constantly produce drag in both circumstances. The need to be able to predict the sound emission of an acoustic source represents an extremely current engineering challenge: in particular, a numerical code that would let the user to listen noise produced by a flyover, since acoustic reports are just numerical statistics and spectrogram plots. In this paper, a numerical formulation is suggested for the prediction of the acoustic emission in the frequency domain. The main task of the project was to develop a program that makes dynamic analysis of the signal taking into account the source movement. Moreover, the simulations predicted the noise levels, thus explicitly accounting for the scattering acoustic effects of incidence and geometrical obstacles as well. Geometrical reflections and absorptions of certain frequencies depending on the material have been comprised in the model
Aeroelastic analysis of an adaptive trailing edge with a smart elastic skin
No full textNowadays, the design choices of the new generation aircraft are moving towards the research and development of innovative technologies, aimed at improving performance as well as to minimize the environmental impact. In the current “greening” context, the morphing structures represent a very attractive answer to such requirements: both aerodynamic and structural advantages are ensured in several flight conditions, safeguarding the fuel consumption at the same time. An aeronautical intelligent system is therefore the outcome of combining complex smart materials and structures, assuring the best functionality level in the flight envelope. The Adaptive Trailing Edge Device (ATED) is a sub-project inside SARISTU (Smart Intelligent Aircraft Structures), an L2 level project of the 7th EU Framework programme coordinated by Airbus, aimed at developing technologies for realizing a morphing wing extremity addressed to improve the general aircraft performance and to reduce the fuel burning up to 5%. This specific study, divided into design, manufacturing and testing phases, involved universities, research centers and leading industries of the European consortium. The paper deals with the aeroelastic impact assessment of a full-scale morphing wing trailing edge on a Large Aeroplanes category aircraft. The FE (Finite Element) model of the technology demonstrator, located in the aileron region and manufactured within the project, was referenced to for the extrapolation of the structural properties of the whole adaptive trailing edge device placed in its actual location in the outer wing. The input FE models were processed within MSC-Nastran® environment to estimate stiffness and inertial distributions suitable to construct the aeroelastic stick-beam mock-up of the reference structure. Afterwards, a flutter analysis in simulated operative condition, have been carried out by means of Sandy®, an in-house code, according to meet the safety requirements imposed by the applicable aviation regulations (paragraph 25.629, parts (a) and (b)-(1))
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