Magnetoelastic materials are obtaining an increasing interest in the last few years. Magnetoelastic wave resonant frequency is the sensory parameter generally used to reliably obtain critical information, nevertheless, it was shown that wave amplitude also is very sensitive to measure displacements or magnetic fields. Both parameters, amplitude and resonance frequency could be used as the "sensitive parameter" in no-contact vibration sensors or stress, flux or magnetic field sensors. To make them advantageous to be used, some problems should be solved: the excitation problem (to induce resonance) and the conversion problem (to transduce frequency or amplitude information into a convenient electric signal); in other words, the signal conditioning problem. The paper describes a signal conditioning technique for magnetoelastic sensors developed by using metallic glass materials. Analysis and synthesis phases of design for the signal-conditioning prototype are presented. From the frequency response analysis of a magnetoelastic metallic glass ribbon, a very low damping factor is pointed out. This means that a stationary oscillation could be easily induced into the ribbon and it was seen that the oscillation frequency changed when the boundary conditions (mechanical stress or magnetic field) changed. So, the ribbon can be used as a sensor. The proposed device (PLG 3) for the sensor signal conditioning is described in detail. Finally, PLG 3 plus a magnetoelastic sensor is used for a no contact vibration measurement and compared to the results from traditional tools.
In this paper an Integrated System to access the wind tunnel CTI (Calibration Tunnel number 1) sited at CIRA (Italian Aerospace Research Center), through a scalable networking infrastructure and supporting multimedia technology, is presented. The reliability and scalability of the porposed architecture, allows the execution of complex tests in a remote laboratory without the presnece of operators on site. The system represents an e-learning support where the instructor and the students, connected to a related web site, can execute an experiment in real-time
The present work is framed inside a broader activity aimed at improving the accuracy of numerical models in predicting the crashworthiness behavior of flexible fuel tanks. This paper describes a comprehensive experimental and numerical study aimed at estimating the impact force of a test article, consisting of a soft nylon bag filled with water, subjected to crash impact tests. In order to understand and improve response predictions, the test article drops freely from different heights, and then strikes onto a rigid plate which is instrumented with different types of sensors. Strain gauges, piezoceramic sensors, and fiber optics are used to measure the strain induced by the impact force during the experiments. To tune the test matrix and the measurement chain parameters, numerical computations are carried out to predict the dynamics of drop impact through FE explicit analyses. Through analysis and comparison with experimental results, a relationship between strain and impact energy correlated with the drop height is established, and the overall accuracy of the entire measurement chain is assessed to determine the effectiveness of such a methodology in a full-scale test on a flexible fuel tank structure.
The current design practice of composite material aeronautical structures imposes the use of knock-down structural material allowables to take into account the high sensitivity to environmental exposure (i.e., moisture, temperature, damages). The “moisture derating factor” comes from specific mechanical test campaign and drastically reduces the advantage of using such materials; but the continuous monitoring of the moisture content of the structure could enable the use of higher design allowables. In the framework of FUSIMCO (Work developed within the frame of the Project FUSIMCO-FUSoliera Ibrida Metallo COmposito-co-financed by MIUR-Italian Ministry of Research with DAC-Campania Aerospace District as beneficiary and Leonardo Company-Aerostructure Division as “prime” partner) project, the aim of this study is to verify the effectiveness of the impedance measurement method as a health-monitoring tool to evaluate the moisture quantity absorbed by an aeronautical composite structure. The method is based on the idea that a composite laminate can be associated with an equivalent electric circuit (EEC). Some electrical characteristics of this EEC can be associated to the moisture content of the laminate. A simple EEC model, mainly capacitive, was used. A frequency sweep was the electric stimulus signal of some electrodes, glued onto the specimens to investigate the EEC parameters variation with respect to the induced moisture content variation (gravimetrically determined). The study confirmed the possibility of effectively using the impedance measurement method as a health-monitoring tool for moisture content evaluation of a composite laminate.
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