Fatigue wizard & MES?

[bjorn_fallqvist]

Hello,

After installing Autodesk Algor 2011, I decided to try out the fatigue wizard. To do so, I created a shaft (quarter model) with symmetry and applied a traction load at one end to compare the safety factor with that of handbook solutions. I now do like this:

1. I enter material data in the fatigue wizard (stress-based), Rm 470MPa and Endurance limit 140MPa (at 1E6 cycles).

2. Calculate everything, with the Kf = 1 (since I have already modelled the stress concentration in the CAD-program).

The problem is that in MES, I get safety factors of 10 for ALL nodes that fatigue wizard lists. Now, if I do the exact same thing in a linear static stress analysis, the results are a lot more reasonable (safety factor around 2, approximately the same as with handbook solutions). Is fatigue wizard not compatible with MES solutions? Should it not just use the element stresses and strains to calculate the fatigue life, regardless of analysis type?

Best regards,
Björn

[Tim.Nong]

Björn,

Have you checked the option "Transient Analysis" in step 4 when using MES solution?

Fatigue Wizard will use the Stress/Strain analysis results to calculate safty factor for each Time Step after checking this option. And please compare the von Mises stress value of MES and linear static stress analysis before running fatigue analysis.

Thanks,
Tim
Algor Simulation QA
Autodesk, Inc.

[bjorn_fallqvist]

Tim,

I have compared the stress results from the linear analysis to MES, and they are the same. I have tried both by activating and de-activating the "transient analysis" tab, and it gives me unreasonable results in both cases.

[Tim.Nong]

Could you please upload your dataset or send an email to zhonglinDOTnongATautodeskDOTcom? Or I can send you a secure ftp site to share your dataset if possible.

This will help a great deal to look into the issue that you are facing.

Thanks,
Tim
Algor Simulation QA
Autodesk, Inc.

[bjorn_fallqvist]

I have an archive file, but it is 220MB. I will send you an email.

Björn

[Tim.Nong]

Thanks for your post, Björn.

In MES, the final Von mises stress will be calculated in the last time step when the load is not a cyclic load in FEA Editor. Therefore, it is required to add a load curve and active the last load case in the step 4 of Fatigue Wizard.

Tim
Algor Simulation QA
Autodesk, Inc.