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Topology optimization of a column

Hi,

I want to do a topology optimization of a column considering the buckling problem. The column has a square cross section (90 x 90 mm) and has 3500 mm in height. Therefor I used shell elements with t=90 because I found out solids do not work for buckling issues in topology optimization. First I ran a simple linear buckling analysis which worked out pretty well. But when it comes to the optimization I dont know how to handle the buckling problem correctly. I used a non-zero base thickness for the shell elements and minimal compliance for the objective. When I set 'buckle' as a dconstraint with a lower boundary of 1.0, the constrains get badly violated. As another dconstrain I used a volumefracion of 0.9.

I dont know if I used the dconstraints correctly ... so does the response 'buckle' stand for the buckling load? I also read about 'LAMA' somewhere and found it in the 'constraint screen' but actually I am not sure how to handle this one properly.

Thanks for your responses in advance!

Regards

Nico

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Altair Forum User

Hi Nico,

Can you share the model file to under stand the problem setup using the file transfer link in my signature below?

Altair Forum User

Hi,

Thank you for sharing the file.

You may have to change the formulation for optimization. You can have buckling constraint and minimize volume as objective.

My observations when I ran just analysis is the buckling load factor is of the order 9E+5, this means the applied load is way to less than the critical load and eventually removes all materials violating your volume fraction constraint.

Even with above suggested formultation I think most of the material will be removed. You can give it a try and make a decision on design.

Altair Forum User

Hi Prakash,

thanks for your advice. You were right: if I minimize volume as objective most of the material will be removed ... but I found out that maximizing the minimal buckle mode with volumefraction as a constraint works pretty well.

Now my next question: can the thickness of a shell structure actually be seen as its density in toplology optimization? So if I want to have a rho_min of 0,45, I can set my base thickness to t_0 = 0,45 * t (with t being the thickness of the shell)?