Inventor Stress Anaysis

[Anonymous]

While working with Stress Analysis I decided to run a simple test to compare to an analytical result.  So I modeled a simple rod, 1" diameter, 10" OAL, A36 steel, fixed on one end with a 100 lbf load on the other.  A simple cantilever.  Analytically, I calculated a max stress of 10.2 ksi and a max deflection of 0.0088".  Inventor shows a max stress of 9.61 ksi and a max displacement of 0.0214".  

I am curious why there is a significant difference?  Did I set the study up wrong or is this just the difference between analytic and numeric modelling?  Or is there another reason?  I'm trying to get a better understanding of what Stress Analysis can and cannot do.  Does anyone have any insight?

I'm running Inventor Pro 2020.2.1 on Windows 7 Pro, Intel Xeon chip with 32.0 GB of RAM.

[JDMather · Accepted solution]

Can you Attach image of your hand calculations and your *.ipt file.

The results should be close on something as simple as your beam.

[andrewdroth · Accepted solution]

Using this I get a deflection of 0.02341

https://www.engineeringtoolbox.com/cantilever-beams-d_1848.html

[Anonymous]

Thanks for taking the time to respond.

As you requested:  my hand calculations and the part I modeled.

If I messed up my Mechanics of Materials calculations I'm going to be embarrassed.

[andrewdroth]

I think on the deflection equation the 8 should be a 3.

[JDMather]

This one was for a metric problem using a different material, but as @andrewdroth indicated - check your formula for displacement.

[Anonymous]

That's just a little embarrassing.  Might be time for some new glasses.

Thanks for taking the time and effort to answer.

But there is still a significant difference between my calculations and the FEM.  I just wish I knew why; then I would be better equipped to understand what the FEM was telling me.

Thanks again for the help.

I also don't understand why this thread was marked "solved" by someone other than me?