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Performing direct-field acoustic test environments on a sandia flight system to provide data for finite element simulation

Conference Proceedings of the Society for Experimental Mechanics Series

Stasiunas, Eric C.; Schultz, Ryan S.; Ross, Michael R.

Aero-acoustic loading has been established as the primary source of excitation for a Flight System at Sandia National Laboratories. However, flight data of this system does not exist, limiting estimations of system or component response in this environment. Therefore, an experimental acoustic simulation was performed on a heavily-instrumented Flight System, using the direct-field acoustic test (DFAT) method with a multi-input multi-output (MIMO) control system. The combination of DFAT and MIMO resulted in attaining uniform and gradient acoustic fields as high as 127 dB OASPL. This paper will discuss the design of the test, the speaker and controller configurations, and the test results of this unique test method. Additionally, an overview of the method used to apply the measured test data to the pressure-loading finite element simulations of the Flight System will be discussed as well.

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TYPE Conference Poster YEAR 2016
ScopusOSTIDOI

Analytical modeling of the acoustic field during a direct field acoustic test

Mesh, Mikhail M.; Stasiunas, Eric C.

The acoustic field generated during a Direct Field Acoustic Test (DFAT) has been analytically modeled in two space dimensions using a properly phased distribution of propagating plane waves. Both the pure-tone and broadband acoustic field were qualitatively and quantitatively compared to a diffuse acoustic field. The modeling indicates significant non-uniformity of sound pressure level for an empty (no test article) DFAT, specifically a center peak and concentric maxima/minima rings. This spatial variation is due to the equivalent phase among all propagating plane waves at each frequency. The excitation of a simply supported slender beam immersed within the acoustic fields was also analytically modeled. Results indicate that mid-span response is dependent upon location and orientation of the beam relative to the center of the DFAT acoustic field. For a diffuse acoustic field, due to its spatial uniformity, mid-span response sensitivity to location and orientation is nonexistent.

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TYPE Conference YEAR 2010
OSTI

Direct-field acoustic testing of a flight system : logistics, challenges, and results

Stasiunas, Eric C.; Skousen, Troy J.; Babuska, Vit B.; Gurule, David J.

Before a spacecraft can be considered for launch, it must first survive environmental testing that simulates the launch environment. Typically, these simulations include vibration testing performed using an electro-dynamic shaker. For some spacecraft however, acoustic excitation may provide a more severe loading environment than base shaker excitation. Because this was the case for a Sandia Flight System, it was necessary to perform an acoustic test prior to launch in order to verify survival due to an acoustic environment. Typically, acoustic tests are performed in acoustic chambers, but because of scheduling, transportation, and cleanliness concerns, this was not possible. Instead, the test was performed as a direct field acoustic test (DFAT). This type of test consists of surrounding a test article with a wall of speakers and controlling the acoustic input using control microphones placed around the test item, with a closed-loop control system. Obtaining the desired acoustic input environment - proto-flight random noise input with an overall sound pressure level (OASPL) of 146.7 dB-with this technique presented a challenge due to several factors. An acoustic profile with this high OASPL had not knowingly been obtained using the DFAT technique prior to this test. In addition, the test was performed in a high-bay, where floor space and existing equipment constrained the speaker circle diameter. And finally, the Flight System had to be tested without contamination of the unit, which required a contamination bag enclosure of the test unit. This paper describes in detail the logistics, challenges, and results encountered while performing a high-OASPL, direct-field acoustic test on a contamination-sensitive Flight System in a high-bay environment.

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TYPE Conference YEAR 2010
OSTI

Model validation of experimental hardware, design versus reality

Conference Proceedings of the Society for Experimental Mechanics Series

O'Gorman, Christian C.; Hunter, Patrick H.; Stasiunas, Eric C.; Hinnerichs, Terry D.; Paez, Thomas L.; Urbina, Angel U.

A detailed model validation study has been initiated to assess model predictions of foam encapsulated components. A bottom-up experimental approach has been used to first characterize the foam material, and then characterize foam/component interaction within increasingly complex systems. This paper presents a summary of the model validation approach at component and benchmark levels and details specific issues identified at the subsystem validation level. Specifically, manufacturing process issues were identified in the hardware which precluded continued validation. A summary of the modal data is given and the issues relating to the manufacturing process are discussed.

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TYPE Conference YEAR 2006
ScopusOSTI
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22 Results