Axial fatigue limit
Beside the LESA method, PragTic misses any influence of load state around an examined point on its fatigue life-time nowadays. The solution is computed at wholly separate points. This means nevertheless, that PragTic cannot recognize for the most of the implemented methods e.g. the differences in life-time of fatigue specimens loaded in repeated tension and repeated bending.
The only solution how to reflect this influence is to give the appropriate axial fatigue limit (in tension, in bending or in rotating bending) to the material parameters used within the specimen, where one of these load types is dominating. This is the case of the high-cycle analyses on smooth specimens, which are gathered in the FatLim database.
Such easily detectable local loads do not appear often in industrial practice. Inability of PragTic to reflect the locality nearby in the fatigue calculation is the greatest problem, if the software should be used for real computations. Filling up of the parameters of the S-N curve in the push-pull load mode is advisable for complicated structures. This type of loading affects the largest area of the specimen and leads to the lowest fatigue limit therefore. The computation thus should produce conservative results.
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© PragTic, 2007
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