
Re: Buckling Analysis
Prasad Bhonsule Apr 23, 2014 12:56 AM (in response to Phil Perlich)Hi Phil, my answers to your questions below
1) Does buckling analysis only use euler's buckling formula? as I understand it, if you are running a buckling study in Simulation Professional, it assumes Linear (Euler) buckling. If you have Simulation Premium, and run a NonLinear study, then you can take into account Nonlinear buckling.
2) Do you always need to use soft springs in the buckling module? No, you don't need to always use soft springs. In fact (I may be wrong), I believe SolidWorks reccommends using fixtures wherever possible to restrain models.
I hope that helps. Please let me know if you require more information.
Kind regards,
Prasad Bhonsule.

Re: Buckling Analysis
Phil Perlich Apr 23, 2014 8:13 AM (in response to Prasad Bhonsule)Thank you for the reply.
1) That seems very limited. I currently have Sim Pro. I'm dissappointed.
2) OK, I put an immovable restraint at the bottom of my column. I then used reference geometry to restrain the top of the column in the transverse directions. Put my load on the top of the column downward in the axial direction. The solver falied. When I added soft springs, it solved.

Re: Buckling Analysis
Shaun Densberger Apr 23, 2014 4:53 PM (in response to Phil Perlich)1) That seems very limited. I currently have Sim Pro. I'm dissappointed.
In FEA, there are two ways to perform a buckling analysis: linear and nonlinear.
 Linear Buckling: This solves for the perturbation of a linear static preload problem via an eigenvalue problem. The results from a linear buckling analysis are unconservative by an unknown amount. Better results can be obtained by rerunning the entire process with a new preload value this is closer to the previously calculated buckling load. This type of analysis is best when used for studying what modes of buckling exist in your design and how the modes of buckling and the buckling load factors are effected by design changes.
 NonLinear Buckling: This isn't "special case" like a linear bucking analysis is. Instead, large displacement and strain formulation are used in conjunction with a nonlinear material model (if needed). This method is more accurate compared to a linear buckling analysis, but will (most likely) still be unconservative due to assumptions on the user's end (homogenous material, free of defects, etc.)
2) OK, I put an immovable restraint at the bottom of my column. I then used reference geometry to restrain the top of the column in the transverse directions. Put my load on the top of the column downward in the axial direction. The solver falied. When I added soft springs, it solved.
Can you post a screen shot of your model (or the model itself)?

Re: Buckling Analysis
Phil Perlich Apr 25, 2014 8:54 AM (in response to Shaun Densberger)Attached is my model.
This column is so simple that I just calculated it by hand, but I thought it would be a good exercise to do an FEA buckling analysis on it.
This column is well below the critical slenderness ratio, but Simulation outputs load factors consistent with slender column expressions.

Re: Buckling Analysis
Jared Conway Apr 25, 2014 1:18 AM (in response to Phil Perlich)Immovable on a solid element?

Re: Buckling Analysis
Phil Perlich Apr 25, 2014 8:49 AM (in response to Jared Conway)I was using beam elements.




Re: Buckling Analysis
Bill McEachern Apr 24, 2014 8:32 AM (in response to Phil Perlich)there are 3 types of bucking:
1) Linear  eigenvalue extraction  is based onthe undeformed shape (no load applied, though it may have one inthe analysis to allow a clac of hte load factor) of the structure.
2) Nonlinear (so called)  you run a static cases of hte load onthe structure and use the resulting deformed stiffness matrix to extract the eigen value (vector). So the load factor is based onthe deformed shape.
3) Post buckling  youloaqd the structure till it collapses and then you can see at which load it lost its stiffness  no eigen value procedure. This procedure can be quite accurate in my experince  well as accurate as you material properties and the fidelity of your boundary conditions allow. I have done calcs where this is in the order of 1% of test data.

Re: Buckling Analysis
Phil Perlich Apr 25, 2014 9:13 AM (in response to Bill McEachern)Can you describe the 2nd and 3rd procedures in a little more detail? Do you have to have Sim Premium to do them?

Re: Buckling Analysis
Bill McEachern Apr 25, 2014 9:18 AM (in response to Phil Perlich)to the extent that it is does it the first two are supported in Sim pro the last one is sim premium. In sim pro it is all automatic for hte load types supported for the "NL" procedure (item 2 above). The reseller course training material explores it. Contact is not supported in any of the procedures.

