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Fatigue SN curve

    • zayeem fazili
      Subscriber

      Dear members,

      I am a PhD student , I am eager to understand SN curve of a material test. If a material is tested the resultant mean SN curve  showS 50 % probablity of survival/failure as accepted by many researchers. Or it depends on the tensile stregth of material. If tensile stregth value coresponds to 95 % Probability of survival as per the standards. In that case would the resultand SN curve be also 90 % probability of survival not the 50 % survival. 

    • danielshaw
      Ansys Employee

      Ansys is not a testing company.  I recommend that you discuss this issue with someone more familiar with fatigue testing.  If the SN curve is developed from fatigue test data, typically an mean curve through the data is developed and used, but some industries require using the 1- or even 2-sigma curve from the test data. If the SN curve was developed from test data, it not clear why the UTS would affect it.  The SN curve is just a statistical fit to the actual test data.  SN curves can be estimated from physical properties (UTS, slope, transition points, etc.).  If SN curve is estimated from physical properties, then it would be affected by the UTS value.

       

    • David Mercier
      Ansys Employee

      Hi, here a discussion where it is explained where to find SN Curves in Ansys Granta products:

      /forum/forums/topic/sn-curve-for-cast-steel-and-gray-cast-iron/

      Once you have found the material you want for your simulation, you can use export functions (and then generate material inputs file) or directly use Granta Selector for example inside Ansys Workbench. Up to you.

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