Computational Modal Analysis of a Hydraulic Pump Support Structure for a Business Aircraft

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Kersten, Simon
Vibrations , Modal Analysis , Finite Element Analysis , Aerospace Design
Computational modal analysis performed using finite element analysis is a well-established method for estimating the modal parameters of complex structures. The work presented here aims to provide an insight into the techniques necessary to model structural components of a business jet fuselage through computational modal analysis of a rear-mounted pump support structure. The results of the computational modal analysis will be used to further aid in the understanding of the vibratory transmission path from the support structure to the fuselage cabin. The frequency response functions were used to validate the finite element model via a visual and analytical comparison against experimental data. The preliminary model was constructed in Altair Hyperworks and a modal frequency response analysis was used to estimate the dynamic response at a discrete set of points on the structure. The model validation study showed a reasonable correlation of the experimental and computational results for frequencies between 100 – 2000 Hz. The average percent difference of the center frequencies for the two models across the 20 – 4000 Hz bandwidth was 11.68 %. Two case studies were conducted on updated models of the pump support structure to provide an understanding of the effect of structural changes on the modal frequency response. Modifications were made to the webbing of the pump support yoke as well as the in-board and out-board isolator plates. These tests confirmed that differences between the frequency responses of the preliminary and updated finite element models can be justified using modal analysis theory. It was found that the structural design changes were not significant enough to impactfully influence the modal response of the structure. The methodology presented in this work provides an outline for future modelling and analysis of this generic business aircraft design.
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