Solved: Reverse cyclic loading

karthur1 · ‎01-30-2018

I have a part (a shaft actually) that will be seeing reverse cyclic loading. I am trying to determine if the design would give "infinite life". I have went through some hand calculations and it looks like it is good, but I would like to put this into FEA and see how it reacts.

Is it possible to do reverse loading in Inventor?

I have not seen anything in help that would even suggest that this is possible. Just thought I would ask.

Thanks.

Kirk

swalton · ‎01-30-2018

My last study of fatigue was an undergrad machine design class 25 years ago...

Could you make a custom material with the "yield stress" set as the infinite life fatigue stress? Take a look at the FOS plot. It seems like anything less than 1 would indicate a finite fatigue life for the component.

I might get fancy and run several studies where the load rotates around the shaft to make sure that the stresses are uniform.

Steve Walton
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mitch.muncy · ‎01-30-2018

Hi Kirk,

swalton is right on here. For a simple loading case for standard metal materials, you can get the stress data and compare it on an S-N curve to figure out durability. It sounds like you're trying to keep the stress under the endurance limit.

If the loading is a bit trickier and you have access to Nastran In-CAD in the collection, you can take advantage of the fatigue module there. There are quite a few overview videos out there if you are interested in this route.

Mitch

karthur1 · ‎01-31-2018

@swalton wrote:

My last study of fatigue was an undergrad machine design class 25 years ago...

Could you make a custom material with the "yield stress" set as the infinite life fatigue stress? Take a look at the FOS plot. It seems like anything less than 1 would indicate a finite fatigue life for the component.

I might get fancy and run several studies where the load rotates around the shaft to make sure that the stresses are uniform.

I'll give that a shot and see how it looks.

Its been 25 years for me too. I had to dust off the old class book to get thru the hand calc.

Thanks,

Kirk