Computational Modal Analysis and Free Size Optimization of an Aircraft Hydraulic Pump Support Structure

This study examines computational modal analysis using FEA modeled structural components on a rear-mounted pump support structure in an aircraft. The goal is to understand the vibratory transmission path to the aircraft cabin, and information regarding dynamic modifications. The frequency response functions were used to validate the FE model by visual and analytical comparison against experimental data. A modal frequency response analysis was used to estimate the dynamic response at a discrete set of points on the structure. A model validation study showed excellent correlation for frequencies between 100--2000 Hz with an average percent difference of the centre frequencies of 9.4% that deteriorated slightly to 11.7% between 20--4000 Hz. Next, modifications were made to the webbing of the pump support yoke and the in-board and out-board isolator plates. These tests confirmed that differences between the frequency responses of the original and modified finite element models can be justified using the modal analysis theory. Webbing removal did not significantly influence the modal response of the structure while isolator plate removal increased the mobility response by 22%. More structural modifications were made using free size optimization, which is advantageous due to minimal changes in structure topology. This reduced the average velocity response magnitude by 6%.