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Stresses into CBEAM or CBAR element.

Hi,

I try to optimize the cross section of a beam using optistruct (diameter and thixkness).

I'm student and I am not sure of what I am doing.

When I try to set the design constraint with optistruct I use the static stress response in order to fix a limit of 300Mpa.

As I'm using 1D element I can't obtain the stress into the cross section of the beam so my design limit (300Mpa) cant be used by Optistruct !!!

Does anybody know if it is possible to obtain such a stress distribution in order to optimze the geometry of the beam cross section ?

Maybe I'm not using the appropriate method in order to optimize the cross section of a cantilever beam !

Regards.

Florent.

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Altair Forum User

Florent,

Using PBAR property for CBAR element and PBEAM property for CBEAM elements you can define stress recovery points.

As you are trying to change the cross section use size optimization. There is a tutorial available called 'Size Optimization of a Shredder ‚Äì OS-4040' which shows how to size optimization on 1d elements.

Altair Forum User

Many thanks for your answer,

I'm going to try with your solution.

In fact I finished by finding a solution :d/ . I used Hypermorh to modify the mesh of the beam by sizing the external diameter and the internal diameter.

For example, when the external diameter is morphed (scalar homothety), we can declare the new shape of the beam as a design variable !!! I did the same with my internal diameter and finally, I obtain fairly good results.

Because, I did this optimization with the Excel Solver (it takes approximatively 5min) my teacher wanted me to validate my Excel spreadsheet results with a commercial optimizer.

The conclusion is, For such an easy example it takes 5min with Excel and 2 days with Optistruct. Moreover Hypermorph could be an appropriate solution but I still have some problem because when I morph the beam the final design tend to create a very very (very) poor mesh !

Thanks a lot for your advice. I'm going to try now.

Florent.