# Buckling comparsion - problem

Discussion created by Lukas Kantor on Jan 4, 2020
Latest reply on Jan 28, 2020 by Lukas Kantor

Hello,

Id like to show you basic example of buckling on rod which I calculated analytic(by hand)

then by Solidworks simulation and Ansys simulation.

In Solidworks i use rod like solid then beam and shell.

In Ansys simulation just beam.

The results are too much different in beam and shell study against analytic result. Where is problem? Only solids are good.

In Ansys everything looks good too.

See images below.

Here is my example.

Analytic results (critical forces) - Solidworks Simulation results - Ansys Simulation results

a) = 54238 N     a) = 71046 N(beam), 30938 N(shell), 54179 N(solid)     a) = 54212 N (beam)

b) = 216950 N   b) = n/a(beam), 123510 N(shell), 215610 N(solid)          b) = 216530 N (beam)

c) = 433907 N    c) = 286470 N(beam), 252310 N(shell), 441200 N(solid)  c) = 441890 N (beam)

d) = 866934 N    d) = 789139 N(beam), 492740 N(shell), 860990 N(solid)  d) = 861040 N (beam)

As you can see. Solidworks is correct only with solid. Shell results are bad but form looks good. Beam results are wrong and form is bad also. There are strange things in beam form. See below.

Pic: Solidworks - beam -  C) example

Pic: Solidworks - beam - D) example (wrong form and also strange things...)

Pic: Solidworks - shell - C) example (form looks good but criticals forces not)

Pic: Solidworks - shell - D) example (form looks good but criticals forces not)

Pic: Solidworks - solid - C) example (everything seems good)

Pic: Solidworks - solid - D) example (everything seems good)

I think everything is set up correctly. For me is important beam study and it does not work for now. Its a simple example so it is pitty that is not working correctly in 10k Fea soft...

Anyone know solution? or whats wrong? Im learning with FEA solidworks...

Thanks for advice : - )