Fatigue analysis Life expectancy problem

Uygi
Uygi Altair Community Member
edited June 2021 in Community Q&A

I am trying to run a fatigue analysis on an automotive part. I have already performed a linear static analysis for worst case loading. Maximum stress was around 23MPa. When I conduct Multiaxial Fatigue analysis, I get life values around 5.4E-16. I cannot figure out my mistake. Can someone please help me?

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Answers

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited June 2021

    Hi,

     

    remember to share more details about your model, what is the material curve, time history, and so on.

    Pictures are also welcome.

  • Poh Soong Tang_20522
    Poh Soong Tang_20522
    Altair Employee
    edited June 2021

    Depending on your load history definition, you may be able to find the element which have life values around 5.4e-16 and check the stress values of that element in one cycle.  Is it still around 23MPa or it is something that is unexpectedly high, i.e. element connected to rigids and etc.?

    If the stress is in expected range, then you need to check your fatigue analysis setup as Adriano has mentioned.  For example,

    - I assume this a stress life fatigue run, so what stress are you monitoring? Abs Max Principle, Signed Von Mises and etc.

    - Check material definition.  Is the material curve in the right unit?  Are the parameters for the S/N curve seemed reasonable?  Is the S/N curve definition based on Range or Amplitude?  By default, OptiSruct is assuming the S/N curve based on range.  If you were using HyperLife, then the S/N curve definition is based on amplitude. 

    - Check your load history definition.

     

    Hope this help.

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