View source for Physics:Fatigue damage spectrum

The '''Fatigue Damage Spectrum''' (FDS) of a vibration is obtained by tracing the fatigue damage experienced by a linear Single [[Physics:Degrees of freedom (mechanics)|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 [[Physics:Spectral density|Power spectral density]] (PSD) of the vibration can be directly used for the FDS calculation.

==Note==

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 ''[[Physics:Extreme response spectrum|Extreme response spectrum]]'' (ERS).

==See also==
[[Fatigue (material)]]

==References==

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

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[[Category:Mechanical vibrations]]

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