Fatigue damage spectrum
The Fatigue Damage Spectrum (FDS) of a vibration is obtained by tracing the fatigue damage experienced by a linear Single Degree of Freedom System (SDOF) according to its natural frequency, for given damping ratio and for a given value of parameter b (this parameter comes from the Basquin law representing the Wöhler curve of the material constituting the structure).
Regardless of the vibratory signal studied (sinusoidal vibration, shock, random or composite vibration); the FDS can be obtained directly from the time history signal. The method consists of :
In the case of stationary random vibration, the Power spectral density (PSD) of the vibration can be directly used for the FDS calculation.
Vibrations can damage a mechanical system as a result of several processes, among which are:
FDS is used according to the second criterion. The first criterion is considered with the Extreme response spectrum (ERS).
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