METHODS OF ANALYSIS OF FLIGHT VIBRATION MEASUREMENTS,
Abstract
A method of analysis of flight vibration measurements is required to provide information for development of design analyses and test procedures. The method of analysis is governed by the objectives of the overall engineering program. The first objective is to design systems whose components will not be subject to severe vibrations in frequency zones of high sensitivity. The second objective is to devise tests which will establish the reliability of the actual system in the presence of realistic vibrations. In the analysis of the flight wave, it would be desirable to extract the exact Fourier component amplitudes corresponding to each multiple of a low fundamental frequency, and thereby produce an exact mathematical representation of the wave. Techniques which are presently available cannot produce such a representation. Rather, they are limited to finding the sums of the squares of the Fourier coefficients over a given frequency band. Information about the instantaneous value of the wave is lost and what emerges is a 'power spectral density' or 'Fourier Coefficient Strength' versus frequency. It is learned that this kind of an analysis, taken with an appropriate electro-dynamical transfer function, will produce root mean square values of any electrical or mechanical quantity at any point. But the instantaneous value of any quantity is unpredictable. One way of making up for the lost information is to measure the output of various electro-dynamical systems when driven by the complex wave. A study can then be made of the percentage of the time the output is above any reference output. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 19, 1955
- Accession Number
- AD0622291
Entities
People
- J. P. Kearns
Organizations
- Johns Hopkins University Applied Physics Laboratory