How to avoid generating free parts (separate parts) in topology optimization?

WEIKANG SONG

Hello everyone.

I made a topology optimization and this is what I got:

I know this optimized structure is reasonable in my case. However, this optimized structure has seperated parts. But due to some special reasons, I need my structure to be a whole, rather than separate parts as shown in the result above.
Is there any way to get a result as a whole without generating free parts? I did not find a suitable setting in the optimization - topology panel or the optimization - opti control panel. Where and how should I set it so that no free parts show up in the optimization result? Or is there any other way?

Gildas_GUILLY

Hello Weikang Song,

In general in such case where you want to guide an optimization, you first need to idenfify why you actually the design to have this specific feature (those "special reasons" you are mensionning). That often helps finding a way to translate it into something that makes sense for the optimisation tool. That could be for manufacturing reason, mechanical reason, etc...
Never forget OptiStruct is basically a mathematical tool, and if we want something from him we need to find a way to express it in a way that makes mathematical sense.
The way you introduce those additionnal items in your optimization are not necessary parameters and settings in the design variable: that can sometime be introduced as additionnal loading, reponses and constraints.

In your particular case, you say you want it to be a single part.
Why ?
Let's say for example this is for pure logistic/handling purpose. You need people that will handle the part to be able to manipulate the part as one single item. If so that would mean you could just add some very slight beams of mater to the current resulting concept to link together all sub-parts.
But you may think this would not be stiff/strong enough --> then you have your reason.
In such case you cant your concept to sustain other type of mechanical loadings that you did not consider in your optimization yet.
In your particular case, that could be an additionnal loading that you ass to your optimization that would challenge your current concept.

Gildas