Qualification of Spacecraft Equipment: Random-Vibration Response Based on Impedance/Mobility Techniques

Rodrigues, Gonçalo; Santiago-Prowald, J.

doi:10.2514/1.29734

Cited by 2 publications

(10 citation statements)

References 9 publications

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“…The authors have shown in previous papers [6][7][8] the advantages of computing the modal frequency response functions of the structure composed by the spacecraft panel and the equipment units using an impedance/mobility condensation method. In such an approach, each subsystem is characterized in a compact and modular way, and the solution of the coupled dynamic response is obtained by the multiplication of the impedance and mobility matrices.…”

Section: A Mechanical Simulationmentioning

confidence: 99%

“…In [6], the expression of H n f in terms of the modal properties of the panel and equipment units is provided. By neglecting the generalized force from the panel base excitation, which allows restricting the mode shapes and the mobility of the panel to the flexible modes only, and after proper manipulation, the modal frequency response function of the acceleration at the I=F to equipment in response to the loads applied to the panel can be written in the form…”

Section: A Mechanical Simulationmentioning

confidence: 99%

“…The physical meaning and the computation of these quantities is thoroughly described in [6]. It can be observed that, in the absence of equipment mounted on the panel, the impedance matrix of the equipment Z e f becomes zero and the coupling matrix C U1 f degenerates to the identity matrix.…”

Section: A Mechanical Simulationmentioning

confidence: 99%

“…It is a further development of previous work by the authors [6][7][8] for computing the coupled dynamic response of spacecraft structures employing the impedance/mobility condensation technique, providing here revised formulations and improved theoretical justifications. The method is based on the separate dynamic characterization of the constituting subsystems.…”

mentioning

confidence: 99%

“…Furthermore, it can be envisaged an application of this method in parallel with the prediction of the response of the panel to base excitation [6]. This will thus provide a complete prediction of the random vibration environment (RVE) for any unit by combining the vibroacoustic and the random accelerations transmitted from the base.…”

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confidence: 99%

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Qualification of Spacecraft Equipment: Early Prediction of Vibroacoustic Environment

Santiago-Prowald

Rodrigues

2009

Journal of Spacecraft and Rockets

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This paper proposes a new, flexible, and accurate method for predicting the vibroacoustic environment, which is a driving load case in the development of panel-mounted spacecraft units. This method accounts for the physical parameters that intervene in the dynamically coupled response of units and panels to the impingement of the sound radiated by the rocket engines. Accordingly, it can simplify the costly overdevelopment imposed by testing standards relying on simple mass formulas and significant safety factors. It quickly provides acceleration and force levels for vibration tests, can be applied during any project phase, and allows for the coupling of models with different levels of maturity, while still avoiding the lengthy processing imposed by finite and boundary element tools. It uses impedance/ mobility for dynamically condensing panels and units in a compact and modular way. The acoustic load experienced by a panel is characterized by means of physical reasoning based on acoustic diffraction and joint acceptance between the mode shapes and diffuse field. Predicted levels are presented for an actual spacecraft panel coupled with several units, and are compared to detailed vibroacoustic analysis using finite and boundary element methods, test results, and ESA and NASA standards. Nomenclature A = integrating range of the panel a = circular plate radius, m C F f = force dynamic coupling between panel and units C U1 f = acceleration dynamic coupling between panel and units c = speed of sound, m=s f = frequency, Hz f co = cutoff frequency, Hz G r f = scaling factor of power spectral density of impinging acoustic field G res = static residual of panel compliance at interface to units, m=N g = acceleration of gravity, 9:81 m=s 2 H n f = modal frequency response H nF f = force modal frequency response j = imaginary unit j 2 nn f = joint-acceptance function k = wave number L = largest side length of a rectangular plate or diameter of a circular plate, m m = mass, kg p = acoustic pressure p 1 = far-field acoustic pressure Sf = structural response power spectral density, g 2 =Hz for acceleration and N 2 =Hz for force S r f = acoustic loading power spectral density, Pa 2 =Hz S a f = spectrum of sound pressure level specified to mission, Pa 2 =Hz y = coordinate in panel U 1 f = acceleration frequency response function Y f f = flexible part of modal mobility matrix Z e f = impedance matrix of units at the interface points exn f = generalized modal force applied to panel y 1 ; y 2 ; f = cross-correlation coefficient of acoustic diffuse field n y 1 = spatial distribution of mode shape of panel fn = matrix of flexible mode shapes of panel Subscripts F = force U1 = acceleration Superscripts T = transpose = complex conjugate

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Section: A Mechanical Simulationmentioning

confidence: 99%

Section: A Mechanical Simulationmentioning

confidence: 99%

Section: A Mechanical Simulationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Qualification of Spacecraft Equipment: Early Prediction of Vibroacoustic Environment

Santiago-Prowald

Rodrigues

2009

Journal of Spacecraft and Rockets

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Vibroacoustic response of stiffened thin plates to incident sound

2021

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A model was developed and applied for predicting the vibroacoustic response of stiffened plates excited by different incident sound fields. A relationship between the Joint Acceptance Function (JAF) and the modal radiation efficiency is derived. This allows a direct calculation for both the vibration response and the sound transmission loss (TL) in the presence of a diffuse field whilst accounting for full vibroacoustic coupling. The response for different structural configurations, plane versus diffuse acoustic excitation and modelling approximations are highlighted, so presenting a systematic quantification of the factors influencing the vibroacoustic response. It is found that vibroacoustic coupling is enhanced by the presence of stiffeners, with the effects for different types of acoustic excitation and the contribution from the modal cross terms being most significant for the TL results.A coupled FE-BE numerical model of stiffened plate and other empirical formulae for unstiffened plate are subsequently used for the validation and verification of the proposed model. The results show that the computational cost of simulation can be significantly reduced with a small loss of accuracy when using the proposed model in comparison to the fully coupled FE-BE numerical model.

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Qualification of Spacecraft Equipment: Random-Vibration Response Based on Impedance/Mobility Techniques

Cited by 2 publications

References 9 publications

Qualification of Spacecraft Equipment: Early Prediction of Vibroacoustic Environment

Qualification of Spacecraft Equipment: Early Prediction of Vibroacoustic Environment

Vibroacoustic response of stiffened thin plates to incident sound

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