Fatigue damage spectrum

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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 :

  • numerically calculating relative response displacement of the mass in relation to its support;
  • establishing a peak histogram, giving the number ni of peaks according to their amplitude;
  • using Miner’s damage accumulation law.

In the case of stationary random vibration, the Power spectral density (PSD) of the vibration can be directly used for the FDS calculation.

Note[edit]

Vibrations can damage a mechanical system as a result of several processes, among which are:

  • the exceeding of characteristic instantaneous stress limits (yield stress, ultimate stress etc.);
  • the damage by fatigue following the application of a large number of cycles.

FDS is used according to the second criterion. The first criterion is considered with the Extreme response spectrum (ERS).

See also[edit]

Fatigue (material)

References[edit]

  • Lalanne, C., Mechanical Vibration and Shock Analysis. Volume 5: Specification Development, Second Edition, ISTE - Wiley, 2009.