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Fatigue Study not giving infinite life when all stresses are below endurance strength

Question asked by Aaron Gradeen on Dec 9, 2014
Latest reply on Dec 12, 2014 by Jared Conway

Hi All,

  I'm doing a fatigue study on a simple assembly. The fatigue study has one loading event which uses the "find cycle peaks" option. There are six static studies which are enabled under the find cycle peaks. 

Loading Events.PNG

I am telling SW to infer SN curve data based on ASME Carbon steel curves which results in a endurance strength of 12048 psi. I apply a 0.9 fatigue strength reduction factor to get down to my desired fatigue strength of 10800psi.


None of the six load cases experience a stress which is above the 12048 psi. For this reason I would expect to get an infinite life. But I don't. I'm using Max absolute principle stress and the goodman correction factor. The maximum principle stress I can find in all my static studies is about 8 ksi and the minimum is about -1.2 ksi. Well within my allowable alternating range even considering the goodman correction. Any thoughts as to what could be causing this? Does solidworks extrapolate that 12048 psi when my cycles go beyond what is in the SN curve data? I do have "infinite life" enabled.