Multi-Axial Fatigue Analysis - What is Dynamic Area results?

[jthomas2SNH8G]

Running a Multi Axial Fatigue Analysis.

I see this "Dynamic Area=3" section in the results after I run successfully.

What does that refer to ?

[John_Holtz · Accepted solution]

Fatigue uses the method of linear superposition: the stress (or displacement, etc) due to multiple loads with different load curve multipliers is the sum of the result due to each load individually.

You have two loads: gravity and a force. The results under the Subcase 1 result branch is due to one of the loads. The results under the subcase DYNAMIC AREA = 3 result branch is due to the other other load. If you had more loads, there would be more "dynamic areas" added to the results. Note that the results are not based on the load curve; the results are based on 100% of the load.

The Fatigue Results branch gives the fatigue results due to the the loads combined per the load curves. The combined stress (and displacement, etc.) result due to the load curve cycles is not given anywhere.

For reference, the attachment to this article includes a PDF that details many aspects of the Multi-axial fatigue calculation. Autodesk Inventor Nastran 2022 Help | How to understand Fatigue analysis in Nastran | Autodesk (edited reply to add link.)

John 

[jthomas2SNH8G]

@John_Holtz 

Thank you for clarifying that.

For reference, the attachment to this article includes a PDF that details many aspects of the Multi-axial fatigue calculation. - Were you going to attach a link or PDF with that response?

[John_Holtz]

Oops. I did forget to add the link! Autodesk Inventor Nastran 2022 Help | How to understand Fatigue analysis in Nastran | Autodesk

(I will add it to my original post, if it will let me edit it.)

John