Learning Forum

[zayeem fazili]

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. 

[Daniel Shaw]

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.