Characterization and Synthesis of Random Acceleration Vibration Specifications

Abstract

Abstract. Random acceleration vibration specifications for subsystems, i.e. instruments, equipment, are most times based on measurement during acoustic noise tests on system level, i.e. a spacecraft and measured by accelerometers, placed in the neighborhood of the interface between spacecraft and subsystem. Tuned finite element models can be used to predict the random acceleration power spectral densities at other locations than available via the power spectral density measurements of the acceleration.The measured and predicted power spectral densities do represent the modal response characteristics of the system and show many peaks and valleys.The equivalent random acceleration vibration test specification is a smoothed, enveloped, peak-clipped version of the measured and predicted power spectral densities of the acceleration spectrum.The original acceleration vibration spectrum can be characterized by a different number response spectra: Shock Response Spectrum (SRS) , Extreme Response Spectrum (ERS), Vibration Response Spectrum (VRS), and Fatigue Damage Spectrum (FDS). An additional method of non-stationary random vibrations is based on the Rayleigh distribution of peaks. The response spectra represent the responses of series of SDOF systems excited at the base by random acceleration, both in time and frequency domain.The synthesis of equivalent random acceleration vibration specifications can be done in a very structured manner and are more suitable than equivalent random acceleration vibration specifications obtained by simple enveloping. In the synthesis process Miles' equation plays a dominant role to invert the response spectra into equivalent random acceleration vibration spectra.A procedure is proposed to reduce the number of data point in the response spectra curve by dividing the curve in a numbers of fields. The synthesis to an equivalent random acceleration J.J. Wijker, M.H.M. Ellenbroek, and A. de Boer spectrum is performed on a reduced selected set of data points. The recalculated response spectra curve envelops the original response spectra curves.A real life measured random acceleration spectrum (PSD) with quite a number of peaks and valleys is taken to generate, applying response spectra SRS, ERS, VRS, FDS and the Rayleigh distribution of peaks, equivalent random acceleration vibration specifications. Computations are performed both in time and frequency domain.

Optimization of Damage Equivalent Accelerated Test Spectrum Derivation Using Multiple Non‐Gaussian Vibration Data

“…To perform life cycle potential damage assessment and test tailoring, Lalanne [14] derived an equivalent PSD from multiple task profiles based on the frequency domain fatigue damage spectrum (FDS). Wijker [15] and Decker et al [16] derived the accelerated test spectrum based on the extreme response spectrum (ERS). The effect of parameter uncertainties (damping coefficient and fatigue exponent) on the root mean square (RMS) value of the derived PSD was studied.…”

On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration

“…The fatigue damage spectrum (FDS) and the extreme response spectrum (ERS) have been used as a quantitative way to take the fatigue damage and overstress damage into consideration for field data [14][15][16][17][18][19][20]. The FDS and ERS are used in the second methodology to derive a damage equivalent Gaussian signal (characterized by a PSD and time duration) from the non-Gaussian signal, so that they can be easily produced on the shaker in the closed-loop frequency domain control mode.…”