Density either 1 or near 0 for all elements

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi,

I'm doing a topologyoptimization with OS and the problem that appears is the following:

When I display the optimization result in Hyperview the density of my elements are either 1 (nondesign_prop) or near zero (0.009) for the design_prop elements. Thats for the 9th Iteration.

There are no error messages during optimization process.

Its a pretty simple concept of a trolley with a few forces apllied. The elements/geometries are either included in design or non-design components.

The objective is to minimize the volume. Therefore there is a volume response.

The forces are all combined in one load collector and there is only one load step. I didn't determine a SPC constraint. Maybe this is necessary?

As you might have recognized, I'm a newbie. So any hellp will be appreciated.

Thanks!!

Greetings Anne

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2010

    Sounds like your optimum is to have no part at all :-k Your problem is not well defined. Perhaps you need to define a displacement constraint?

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2010

    Thanks for the answer.

    Do I always have to define a displacement constraint? As I understood from the manual etc. this it not necessary? I tried it with displacement constraints on design elements as well- same results. Maybe the displacement constraints have to be assigned to non design space?

    I also thought about that maybe the forces are so low that there actually is no material needed. But the forces are assigned directly to design elements, therefore should there at least be material at these elements.

    Greets Anne

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2010

    Dear Anne,

    it looks like your optimization problem is not properly defined. An objective to minimize the volume would in general lead to a 'empty' volume, if no proper contraints are taken into account.

    You might want to have a look at tutorial Design 'Concept for a Structural C-clip - OS-2000'. This is a simply example with a volfrac-objective, displacement constraints and element densities as design variable.

    Or tutorial 'Design Concept for an Automotive Control Arm - OS-2010' where the concept of design and non-design space is taken into account.

    Regards,

    Stefan

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