Evaluation of the Force Limited Vibration Semi-Empirical Constant for a Two-Degree-of-Freedom System

A study was conducted to evaluate the force limited vibration semi-empirical constant for a two-degree-of-freedom system (TDFS). The random vibration input was specified as an acceleration spectral density (ASD), called power spectral density, with ASD units of g2/Hz. The idea behind force limiting was to notch the test ASD in such a way that the maximum interface force spectral density never exceeded. Force sensors were installed between the test article and the shaker during implementation of force limiting, to monitor the interface force during testing. The base-excited TDFS was selected for analysis, as it was the simplest system exhibiting the vibration absorber and frequency shift effects and represented a spacecraft mounted on a rocket or a spacecraft component mounted on the spacecraft structure. The investigations also revealed that the maximum force and the maximum acceleration occurred at one of the damped resonant frequency of the TDFS.