FATIG computes fatigue damage/ fatigue life using the stress rms (root mean square) value, the total number of cycles, and S–N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner’s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner’s rule. The integration is carried out over all stress amplitudes.

This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user.

It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

This work was done by Constantine Michalopoulos of The Boeing Co. for Johnson Space Center. For further information, contact the JSC Innovation Partnerships Office at (281) 483-3809. MSC-24975-1

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