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Validation of equivalent viscous damping methodologies

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An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite’s dynamic environment, it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the coupled loads analysis (CLA). When working with finite element models, the materials’ damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations, and so the resolution of the equations of motion must be done in the time domain. Unfortunately, in the CLA, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary in this case. Nevertheless, this transformation is not trivial. There exist many methodologies for computing an equivalent viscous damping (EqVD) matrix of the system which can be used in transient analyses. This paper describes the results obtained from the validation of EqVD methodologies used in the European Space Agency. This work identifies the limitations of these methodologies and comes up with an enhanced methodology that predicts more reliable results.

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I would like to thank Sebastiaan Fransen and Sylvain Germs for their extraordinary help in this work as well as to thank Nicolas Thiry for his help in implementing the enhanced methodology in the CLA Toolbox to obtain the results for real Vega in-flight events.

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Correspondence to Xavier Vaquer Araujo.

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Vaquer Araujo, X., Fransen, S.H.J.A., Germès, S. et al. Validation of equivalent viscous damping methodologies. CEAS Space J 4, 31–39 (2013).

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