Software for Selecting Modes of Vibration of a Structure

A computer program facilitates the selection of the dominant modes of vibration of a structure - especially the dominant modes that interact with specific locations on the structure. This program is intended for use in conjunction with any of the various vibration-mode-analysis programs based on the finite-element method (FEM). The program was written to satisfy a need to accurately and quickly sort through enormous amounts of information about the vibrational modes of the developmental X-33 aerospace launch vehicle in order to select the dominant modes and thereby reduce the subsequent computational burden of analyzing the vibrations of the vehicle. In the X-33 application, the program has been used to determine which modes interact most with specific locations and pieces of equipment that affect and are affected by stability or instability with respect to (1) flight control and (2) a phenomenon, called "pogo" (because it is reminiscent of oscillations like those of a pogo stick), which involves deformations of liquid-oxygen plumbing combined with sloshing and/or fluctuations in pressure of the liquid oxygen inside the plumbing. The program could also be adapted for use in analyzing the vibrations of structures other than that of the X-33.