Fatigue - Question about Input method : Estimate from UTS

Altair Forum User

Hello all,

I would like to do a Fatigue analysis of an aluminum structure  (I used the Aluminium 2024 T861, UTS = 496 MPa) . In the  Optistruct tutorials (OS-1340: Fatigue (Stress - Life) Method.) the values of the SN curves (SRI1, b1, NC1), for aluminum alloy, are calculated from the UTS with these formulas : SRI1 = 0.131*UTS^1.526 ; b1 = 0.379 -0.175*log(UTS). However, in these formulas, the mean stress (or the ratio) is not taken into account and for me, a SN curve is for a fixed mean stress (or a fixed ratio).

So, where is this mean stress considered in the process?

 

 

 

 

 

Rahul Rajan_21763

Please download our free eBook on Fatigue analysis with OptiStruct using below link.

https://altairuniversity.com/free-ebook-learning-fatigue-analysis-with-optistruct/

 

Please refer 2.1 chapter for stress life approach ,assumption and limitation part.