Transient Synthesis Using a Fourier Transform Envelope: An Alternative to Swept-Sine Vibration Testing

Abstract

Transient vibration test offer an alternative to the conventional swept-sine vibration test, with controllable conservatism. A method of deriving a single vibration test transient from several spacecraft flight transients is described. These transients were from different physical locations on the spacecraft. The test transient was derived by taking the inverse Fourier transform of an envelope of the Fourier transforms of the flight transients. The inverse transformation was performed using the real and imaginary parts of that Fourier transform forming the envelope amplitude at each frequency. The test transient therefore has the same frequency content and maximum amplitudes as the flight transients. A generic test transient was therefore produced that duplicates many operating conditions at separate physical locations. It could be applied to many different structural components of a spacecraft, simplifying a vibration test program. The transient vibration test produces significantly less overtest than a conventional swept-sine vibration test.