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Publicatie

IDENTIFYING THE STRUCTURAL BEHAVIOUR OF A SPECIMEN DURING SPACECRAFT ACOUSTIC TESTING BY OPERATIONAL MODAL ANALYSIS

Boekbijdrage - Boekhoofdstuk Conferentiebijdrage

Environmental testing is a necessity to ensure the survivability of hardware during launch of space vehicles. Particularly during the ignition and liftoff launch stages the main source of dynamic loading is characterized by a not deterministic acoustic environment. Hence, the environmental acoustic test becomes a fundamental qualification test to evaluate if an aerospace structure (e.g. payload), system or component can withstand the vibratory load it will encounter during its operational life. In this paper, the possibility is explored to apply Operational Modal Analysis to characterize the structural dynamics of an antenna reflector during a so-called direct field acoustic excitation (DFAX) test. In such a test, very high sound pressure levels are achieved by using a large amount of professional audio speakers installed around the test specimen. Microphones are used for feedback control to achieve the desired properties of the sound field (overall sound pressure level, uniformity, coherence). In addition, also the structural vibrations of the specimen are monitored using accelerometers. The purpose of the paper is to track and compare the modal parameters of the specimen during various testing phases for an enhanced understanding of the structural behaviour under acoustic loading. Classical Experimental Modal Analysis will be applied to data from a preliminary impact test and Operational Modal Analysis will be applied to data from open-loop system identification tests, and closed-loop controlled tests at multiple sound pressure levels. This allows also to study potential nonlinear structural behaviour. The analysis of the structural vibrations also led to interesting observations related to the direct sound field.
Boek: 7TH IOMAC: INTERNATIONAL OPERATIONAL MODAL ANALYSIS CONFERENCE
Pagina's: 114 - 117
Aantal pagina's: 4
ISBN:978-3-8440-5247-3
Jaar van publicatie:2017