Results comparison between PrePoMax, SolidWorks SimulationXpress, & Textbook Equation

General Questions
1

Dear Forum,

I have been watching ProPoMax tutorials on YouTube to learn how to use the software. The software seems pretty straightforward and intuitive to use. Thank you FEAnalyst for the excellent tutorials.

I started with a relatively complex FEA simulation and the results appeared to be a bit off. I thought that maybe I was doing something wrong.

So I went back to “basics” and modeled the classic cantilevered beam with an applied a load to the distal end of the beam. I used both PrePoMax and SolidWorks Simulation Xpress to run and FEA simulation. The results were VERY different.

So I reverted to a very basic analysis using the “textbook” equations for stress and deflection (6061-T6 aluminum). This is what I discovered. The “textbook” equation correlates well to the SolidWorks SimulationXpress simulation…NOT the ProPoMax simulation.

Take a look at the last image labeled TEXTBOOK EQUATION and compare the results at the bottom of the table for both stress and deflection to the simulation results from PrePoMax and Solidworks SimulationXpress.

I would appreciate any input that you may have.

TIA,
–Neal

image
image2017×813 269 KB

2

I don’t see much in the screenshot showing the setup but didn’t you apply the load as concentrated force in PrePoMax by any chance ? If not, can you share the .pmx file ?

3

Yes. The load was applied as a concentrated load in both the SW and PPM simulations.

–Neal

4

Then that explains too large results in PrePoMax. Check this post: Don't apply concentrated force load to surfaces

1 Like
5

BTW, I have tried to upload my .pmx file but the Forum limits my ability to upload files because I am a NEW user.

–Neal

6

Now you should be able to upload files.

7

Dear FEAnalyst,

Thank you. I just looked at the link that you provided and I changed the load from a CONCENTRATED to a SURFACE TRACTION load. Now the numbers correlate extremely well. Thank you.

As a sanity check, I counted 14 nodes on the surface face that I had previously selected with a concentrated load. I then multiplied 5N X 14 nodes = 70N and applied this load as a surface traction load to see if I would get the same result as a 5N concentrated load applied to 14 nodes. I did not see the same stress and deflection as I saw previously with the concentrated load that resulted in huge stress and deflection.

I tried to attach the .pmx file and I am still not allowed. I may need to close and re-open the browser? I will try this momentarily.

Thank You
–Neal

8

Dear FEAnalyst,

Please see the attached file. I have both loads, concentrated and surface traction, in the .pmx file. I just deactivated the concentrated load. You can obviously toggle back and forth.

–Neal

test_cantilever.pmx (1.4 MB)

9

Yeah, looks good and agrees with hand calcs now. With surface traction load, you can achieve the desired effect. Concentrated force is usually applied only to reference points of rigid body constraints.

1 Like