Fatigue S-N Curve Discrepancy on X-Y Plot

[Anonymous]

Hi All,

I'm setting up a Fatigue Analysis study in Nastran In-Cad 2018. I've input the following parameters.

Su = 310

Se = 95

No = 1000

Ne = 5E8

Solving for b:

b = [LOG(Su)-LOG(Se)]/[LOG(Ne)-LOG(No)]

b = 0.09012823

The attached images show the results of the "Show X-Y Plot" button. The (No,Su) point is correct (1000,310). The (Ne,Se) point is shown as (3385,95). 

My question is, why is the displayed value Ne not identical to the input parameter 5E8? Will this affect the results of the simulation or is this simply a display error?

[John_Holtz · Accepted solution]

Hi @Anonymous

The XY Plot is wrong. (It incorrectly calculates it using a linear plot instead of a log-log plot, so it implies the wrong value for Ne.)

This does not affect the results.

______________________________________________________________

If my post answers your question, please click the "Accept as Solution" button. This helps everyone find answers more quickly!

[Anonymous]

This really is pathetic of Autodesk not to fix this after 5 years already. What kind of amateur software company can't get its act together after 5 years?

It's just this kind of rubbish attitude that stopped my company buying the CFD software because it couldn't even give us the Cd for a Ø1m ball.