Contraining a hole as a void that will not expeirence deformation

exx077

Hello,

 

I would like to simulate a void as a region within my model that should not experience any deformation - to not damage any structure that may be place there e.g. a bearing.

This is to be for a topology optimisation simulation, then how (if it is possible) can it be approached so that the optimal topology maintains the shape of the void?

 

To expand, if I have a circular hole where a bearing should be placed and I do not want the deformation of the model to damage this bearing, how can I contrain the hole to maintain its shape during the topology optimisation?

 

I would not like to use RBE2s or a nondesign space as this will effect the way the load paths are transferred.

Will RBE3s work?

If not, is there an alternative?

 

Thank you in advance.

Sanjay Nainani_20973

Hello,

 

Can you please post some snaps of what you are trying to do?

 

Thankyou

exx077

Hello @Sanjay Nainani,

 

I would like the largest circular hole to be shape preserving as a bearing will be placed in here.

Therefore, I would like the the topology in the design space (yellow) to account for this.

 

Thanks.

 

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QuyNguyenDai

About BC, with constraints '123' at center of small hole (on your picture), how you can apply two forces at big hole?

 

exx077

Hello @Q.Nguyen-Dai,

 

This image of the model is not the most up to date file, it is just one I have screen shots available for.

The forces are applied to RBE3s

The constraints are applied to RBE2s (the constraint is DOFs 123456, but you cannot see this as 456 are hidden by the model).

 

However, the focus of my question is how to apply BCs to the largest hole so that it will not deform but without inducing artificial stiffness (like RBE2s may do).

 

Thanks

 

<?xml version="1.0" encoding="UTF-8"?>

QuyNguyenDai

Do you mean that the inner cylindrical surface of big hole should be contrainted? Undeformable surface?

Is there a shaft or something in big hole?

 

exx077

Hello @Q.Nguyen-Dai,

 

I do mean this. I would like the shape of the inner surface of the largest circular hole to be uneffected by the deformation of the model.

If there was to be a bearing placed within this hole I do not want it to be damaged by the deformation of the model under loads.

Is it possible to achieve this?

 

Thanks

QuyNguyenDai

You have always deformation of the hole. The good way is to simulate also the bearing with real stiffness (in your case, the most important is radial stiffness). And you define contact condition between them.

 

exx077

Hello @Q.Nguyen-Dai,

 

What do you mean by this?

Altair Forum User said:

The good way is to simulate also the bearing with real stiffness (in your case, the most important is radial stiffness). And you define contact condition between them.

 

What do I use to introduce radial stiffness?

 

Thanks

QuyNguyenDai

Hmm, maybe you need something like bushing/bearing element? I don't know if this type of element exists in Optistruct.

For simplification, I think you can consider that the bearing is perfectly rigid for optimisation analysis.

exx077

Hello @Q.Nguyen-Dai,

 

I would be keen to know if there is a type/arrangement of 1D elements that could be used to simulate this.

 

I have already tried using RBE2s to support the large hole as rigid and this does not produce a valid structure.

Maybe there is another way I am unaware of.

 

Thanks

QuyNguyenDai

Maybe try to define a contact 'node <-> rigid_surface' for inner face of big hole?

exx077

Hello @Q.Nguyen-Dai,

 

How do I define a contact?

Do I need to create another body within the hole (to represent the bearing) and then define the contact between them this way?

 

Thanks

QuyNguyenDai

Yes, you can do that. Make new body becomes 'rigid' by using high value of Young modulus for example (10x is ok)