1,721,083 research outputs found
Design of a VLA Vertical Control Surface with LRTM Technology
No full textThe present work is connected to a research project that faces the study of low-cost manufacturing technologies and processes of aeronautical structures made of composite material, referring to aircraft belonging to General Aviation (GA). In the specific, the main purpose of this work consists in the design and manufacturing of the vertical control surface of an aircraft belonging to the VLA class using Light Resin Transfer Moulding (LRTM). Starting from the geometrical characteristics of the control surface and the peculiarities of the related aircraft, the relative load distribution has been calculated according to the requirements expressed in Appendix B of CS-VLA regulations. Using a numerical simulation software for finite element analysis, the load, calculated by the procedure in question, has been used as input to the FEM model for the purpose of structural design, i.e. for the choice of the materials and of an appropriate stacking sequence. Once the model has been completely defined, it has been possible to design and to fabricate the moulds for the following phase, which consists in the production of the prototype. Following the production process, the last part of the work focuses on the preparation and the implementation of an experimental campaign that aims at verifying the quality of the infusion process (C-Scan) and of the structural properties of the component, paying attention to the comparison with the previously obtained numerical result
Preface to the Special Issue on the New Frontiers of Acoustic Modeling and Optimization
Full text linkThe field of acoustics involves the study of sound propagation, both in free and closed
environments, through the development of both forecasting simulations and experimental
techniques [1–8]. Currently, such science finds its applications covering several engineering
sectors, especially when it is necessary to evaluate the sound response in mid- and high frequency ranges. The purpose of acoustic modeling is to design “systems” (aeronautical,
buildings, engines, electronic, etc.) that are more comfortable and functionally more
efficient. From this perspective, the development of effective tools for acoustic prediction
and optimization is a challenge for the research community, as the qualification processes
need to be streamlined to reduce high computational/testing efforts. The main issues of
theoretical modeling include the discretization of disturbance sources, stochastic signal
processing, active/passive noise control studies, the optimization of genetic algorithms,
and neural network implementation, which are among the most interesting topics yet
to be covered in-depth. For this Special Issue (belonging to the section “Acoustics and
Vibrations”), the Editors encourage the submission of novel contributions (papers, technical
reports, and broad reviews) from members of the technical-scientific community involved
in the advancement of predictive methods and in the study of solutions aimed at noise
identification/optimization. This initiative will help readers understand various acoustic
modeling issues with comprehensive details. Research methods can include numerical
validations, experimental studies, and the development of new certification standards,
presenting the state-of-the-art results that will have a significant impact on academic interest
and industrial growth. Potential future directions could be presented, relying on advanced
trends, but also on existing research limitations
Vibration parameters for impact detection of composite panel: A neural network based approach
Full text linkThe need for reliable methodologies for structural monitoring is certainly a current line of research in many engineering sectors. The detection of the impact on composite materials is in fact a recent subject of study, aimed at safeguarding the mechanical integrity and improving the useful life of structural components. In such a context, the work deals with evaluation of the use of neural algorithms for localizing the position of the impacts on composite structures. Starting from FE (finite element) simulations, representative of the dynamic response of a CFRP (Carbon Fiber Reinforced Polymer) panel as a benchmark, the approach has been finally validated experimentally by modal parameters identification
Strain state detection in composite structures: Review and new challenges
Full text linkDeveloping an advanced monitoring system for strain measurements on structural components represents a significant task, both in relation to testing of in-service parameters and early identification of structural problems. This paper aims to provide a state-of-the-art review on strain detection techniques in composite structures. The review represented a good opportunity for direct comparison of different novel strain measurement techniques. Fibers Bragg grating (FBG) was discussed as well as non-contact techniques together with semiconductor strain gauges (SGs), specifically infrared (IR) thermography and the digital image correlation (DIC) applied in order to detect strain and failure growth during the tests. The challenges of the research community are finally discussed by opening the current scenario to new objectives and industrial applications
Acoustic properties of materials: A comparison of numerical and experimental methods
Full text linkAcoustic simulations provide today a valid tool to simulate complex environments and complex interaction between acoustic and structure. Multiple methods are nowadays available with different degrees of accuracy and different applications. Simulation methods cover a wide frequency range with FE methods dominating the low frequency range. SEA mostly covers high frequency range with BEM covering an intermediate frequency range. Ray-tracing can work on the entire frequency range and is used when a large domain must be simulated. These methods require acoustic properties of materials to be implemented such as acoustic impedance or absorption and STL. The aim of this paper is to show different methods to provide these properties and discuss about the equivalence/difference of the numerical and experimental approaches under specific assumptions
SISO Piezo based circuit development for active structural vibration control
Full text linkThis paper deals with the issue of developing a smart vibration control platform following an innovative model‐based approach. As a matter of fact, obtaining accurate information on system response in pre‐design and design phases may reduce both computational and experimental efforts. From this perspective, a multi‐degree‐of‐freedom (MDOF) electro‐mechanical coupled system has been numerically schematized implementing a finite element formulation: a robust simulation tool integrating finite element model (FEM) features with Simulink® capabilities has been developed. Piezo strain actuation has been modelled with a 2D finite element description: the effects exerted on the structure (converse effect) have been applied as lumped loads at the piezo nodes interface. The sensing (direct effect) has instead been modelled with a 2D piezoelectric constitutive equation and experimentally validated as well. The theoretical study led to the practical development of an integrated circuit which allowed for assessing the vibration control performance. The analysis of critical parameters, description of integrated numerical models, and a discussion of experimental results are addressed step by step to get a global overview of the engineering process. The single mode control has been experimentally validated for a simple benchmark like an aluminum cantilevered beam. The piezo sensor‐actuator collocated couple has been placed according to an optimization process based on the maximum stored electrical energy. Finally, a good level of correlation has been observed between the forecasting model and the experimental application: the frequency analysis allowed for characterizing the piezo couple behavior even far from the resonance peak
Study and experimental test of Peltier cells for an energy recovery system in a renewable energy device
No full textThe present work focuses its attention about the need of implementation of an energy recovery system for a renewable energy device as photovoltaic cells. In a specific way the present paper is addressed to the evaluation of a potential use of Peltier cells to recover waste heat of PV, using the Seedback effect. An overview of Peltier cells, mainly focused on their functionality, properties and possible applications, is initially presented. The results of an extensive experimental test campaign is then presented; these tests have mainly been dedicated to the evaluation of Peltier cells properties in the electrical conversion of heating energy produced and/or not dissipated during the photovoltaic phenomena in siliceous PV cells. The last part of the work presents the results of a parallel test campaign where Peltier cells have been used as thermoelectric cooling devices, in the aim to improve the PV cell performance. In fact the efficiency and technical lifetime of these latter elements, is strongly affected by temperature of photovoltaic cell. This point and the dissipated heat are fundamental topics for every installation but above all in the cases of regions with a very hot climate or for concentrated photovoltaic plants
Citofluorimetria a flusso, RT-PCR e microscopia confocale applicate alla soluzione di uno stesso problema. La biologia molecolare a supporto della diagnostica veterinaria e al controllo degli alimenti contenenti OGM.
No full textCitofluorimetria a flusso, RT-PCR e microscopia confocale applicate alla soluzione di uno stesso problema. La biologia molecolare a supporto della diagnostica veterinaria e al controllo degli alimenti contenenti OGM
Automotive Materials: An Experimental Investigation of an Engine Bay Acoustic Performances
No full textIn this work an extensively experimental analysis aimed to verify the sound insulation properties of the engine bay of a commercial passenger car is carried out, evaluating the possibility to adopt different sound absorbing materials, to be applied under engine cover nylon skin, in the place of commonly used polyurethane foams. Experimental tests were performed on the vehicle at different stationary operating conditions, employing typical pressure microphones for far field measurements, according to the related prescribed standards. A limited number of materials has been initially selected through a preliminary analysis, and then employed for creating different engine cover configurations, which were subsequently tested in real engine operating conditions. For a good understanding of the obtained results, an experimental investigation through an innovative in situ impedance method aimed to assess acoustic properties of each considered material has been also performed. Among all the tested materials, only one able to ensure better acoustic performance at mid and high frequencies with respect to the already existing cover configuration, has been finally identified, after considering other selection criteria such as an adequate high temperature resistance and the most cost-effective solution. Future analyses will regard investigations on the use of additional materials, for solving problem in attenuating engine noise also at low frequencies
Rapid selection of phge-resistant mutants of Streptococcus thermophilus by immunoselection and cell sorting
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