How would I apply a load to the inside of a structure?

Shalmi Gurunathan
Shalmi Gurunathan Altair Community Member
edited April 3 in Community Q&A

Hello, I am trying to perform topology optimization to minimize compliance on a wing, and I have modeled it in two parts--the skin and the inside structure, both solids. The skin is the non-design part, and the inside structure is the design part. The loads are however applied on the skin. When I try to perform optimization, optistruct shows the error 2148 "invalid design problem. all sensitivities of objective are zero." When i make the skin to be optimized as well, the optimization happens without any problems, but only the skin gets optimized, but i want to optimize the inside structure. In fact, the inside structure feels no stress/load at all in the result.

I want to be able to keep the skin as non-design, and the loads should be applied on the skin only, but i want the inside structure to be optimized, even though the loads are not directly applied onto it. Is there any way to rectify this situation? I also don't know if there is a way to sort of "connect" these surfaces without any bolts, screws, etc. so that the load is indirectly transferred. If there is such a facility please let me know so i can try it out. I have run the model without any objective, just by itself, and it runs fine. I have also attached the model below. Any suggestions are appreciated. Thanks.

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Answers

  • Adriano_Koga
    Adriano_Koga
    Altair Employee
    edited April 2

    how are you modeling the connection between ribs and skins?

    probably they're not connected.]So to simplify your model, you could create a TIE/FREEZE contact between skin and ribs in order to have them connected and trasnfer loads.

     

    In your case the message of zero sensitivities is due to the lack of relevant loads reaching the ribs, because there's no connection. So if there's no load, OptiStruct cannot calculate where to keep or remove material from your model.

     

    The attached example uses contacts in order to connect parts.

     

     

     

  • Shalmi Gurunathan
    Shalmi Gurunathan Altair Community Member
    edited April 3
    Adriano A. Koga_21884 said:

    how are you modeling the connection between ribs and skins?

    probably they're not connected.]So to simplify your model, you could create a TIE/FREEZE contact between skin and ribs in order to have them connected and trasnfer loads.

     

    In your case the message of zero sensitivities is due to the lack of relevant loads reaching the ribs, because there's no connection. So if there's no load, OptiStruct cannot calculate where to keep or remove material from your model.

     

    The attached example uses contacts in order to connect parts.

     

     

     

    Thank you! That helped :)

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