Problem with ANSYS Workbench deformed shape on Eigenvalue Buckling

Metallic · March 12, 2019, 21:21

Hey guys,

I am trying to do linear buckling analysis of a composite material wall and for a publication of mine and i am getting "artifacts" in the results of the analysis. The deformed shapes eigenvalue buckling returns seem too exaggerated and even on low scaling can't be read or presented. Despite all that, my main concern is that the buckling seem to cause those deformation in places that somebody could not expect (from classic engineering and beam theory).
What is going on guys im confused?? Any similar experience? I was thinking that this may be caused by contact algorithm but i tried with a simple hollow square steel beam and still this malfunction is caused.

Also ansys linear buckling seems to give too conservative results in my opinion, do you agree with that? How do you perform buckling analysis?

karachun · March 15, 2019, 04:26

Set deformed view scale to get reasonable deformation. Magnitude of displacement in linear buckling analysis don’t have physical meaning, it only describe deformed shape, like displacement in normal modes analysis.

What is type of your structure? Look like beam with rectangular section. What buckling shape you expect?
Buckling workflow is like Hand calc. (if possible)->Linear buckling->Nonlinear buckling with imperfections. If result of linear and nonlinear buckling are close then you are comfortable with linear buckling and can perform only this type of analysis for similar structures.

Metallic · March 15, 2019, 09:11

Hey Alexander,

Thanks for your response. I know about the view scale but still deformation is quite large for 15% but i guess that's it. It is only a visualization for the modes but i wish it was a bit more refined, so it could be presented in a better manner.

The structure is a hollow steel section. I am using it to evaluate Ansys settings and parameters on buckling so later i could analyse a more complex and more demanding structure for my paper and for production.

I will perform hand calculations with the EN1993-1-1 and compare them to my linear analysis to have a better understanding of the load factors. Later, i might also try nonlinear stepped buckling analysis to compare those results too.

Do you know when performing buckling analysis in a structure with multiple materials, if the factor is calculated with the occurrence of yield in just one of the materials, or in the sum of them?

I will keep you posted about this. ��

March 12, 2019, 21:21	Problem with ANSYS Workbench deformed shape on Eigenvalue Buckling	#1
Metallic New Member Thomas Join Date: Jan 2019 Location: GR Posts: 4 Rep Power: 7	Hey guys, I am trying to do linear buckling analysis of a composite material wall and for a publication of mine and i am getting "artifacts" in the results of the analysis. The deformed shapes eigenvalue buckling returns seem too exaggerated and even on low scaling can't be read or presented. Despite all that, my main concern is that the buckling seem to cause those deformation in places that somebody could not expect (from classic engineering and beam theory). What is going on guys im confused?? Any similar experience? I was thinking that this may be caused by contact algorithm but i tried with a simple hollow square steel beam and still this malfunction is caused. Also ansys linear buckling seems to give too conservative results in my opinion, do you agree with that? How do you perform buckling analysis?

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March 15, 2019, 04:26		#2
karachun Senior Member Join Date: Nov 2015 Posts: 244 Rep Power: 11	Set deformed view scale to get reasonable deformation. Magnitude of displacement in linear buckling analysis don’t have physical meaning, it only describe deformed shape, like displacement in normal modes analysis. What is type of your structure? Look like beam with rectangular section. What buckling shape you expect? Buckling workflow is like Hand calc. (if possible)->Linear buckling->Nonlinear buckling with imperfections. If result of linear and nonlinear buckling are close then you are comfortable with linear buckling and can perform only this type of analysis for similar structures.

March 15, 2019, 09:11		#3
Metallic New Member Thomas Join Date: Jan 2019 Location: GR Posts: 4 Rep Power: 7	Hey Alexander, Thanks for your response. I know about the view scale but still deformation is quite large for 15% but i guess that's it. It is only a visualization for the modes but i wish it was a bit more refined, so it could be presented in a better manner. The structure is a hollow steel section. I am using it to evaluate Ansys settings and parameters on buckling so later i could analyse a more complex and more demanding structure for my paper and for production. I will perform hand calculations with the EN1993-1-1 and compare them to my linear analysis to have a better understanding of the load factors. Later, i might also try nonlinear stepped buckling analysis to compare those results too. Do you know when performing buckling analysis in a structure with multiple materials, if the factor is calculated with the occurrence of yield in just one of the materials, or in the sum of them? I will keep you posted about this. ��