SimScale CAE Forum

Setting position tolerance

Hi Anna,

If we were to use bonded contact for a weld connection, is it necessary to have a set value for the position tolerance? If so, what is the recommended position tolerance?

Regards,
Wan Hao

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Hi @chaiwanhao,

I think the default tolerance setting should suffice in this case, but let’s see if my colleague @rszoeke has any more suggestions. What type of weld application are you working on?

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Hi Anna,

https://www.simscale.com/workbench?publiclink=d51c5ca7-053e-443a-9e98-8c33529c599a

If the small cylinder (shown in the picture above) is fully welded onto the plate, isn’t the position tolerance of the bonded contact zero?

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Hi @AnnaFless and @chaiwanhao . For a contact on SimScale you always have a master and a slave assignment. For every slave node one searches for the nearest master element. If no position tolerance would be active, all slave nodes would be bonded to their respective master element. If a position tolerance is active, only the slave nodes would be connected to their master element, if the distance is below the position tolerance. The automatic setting takes as tolerance value 1/10 of the characteristic element length on the slave surface in the manual setting the user defines the tolerance value.

So if your slave surface is on the cylinder and the cylinder lies exactly on the other part, every tolerance value will result in the same since all nodes will be connected.

On the other hand, if your master would be on the cylinder, you should definitely activate a position tolerance since you only would want the nodes “close” to the cylinder being connected to it.

I hope this answered your question, I’ll be here if you need more assistance.
Best,
Richard

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Hi @rszoeke,

Why is this so? Is it because of the mesh size?

In the case of the project I posted, the appropriate master surface should be the plate, and the slave surface should be the cylinder. This is because the surface of the plate has a coarser mesh as compared to the cylinder. Am I right?

Yes, the slave surface should be the more refined one and if possible also the smaller one (for computational efficiency).

So there’s no need for a position tolerance, right?

No, in your case not. And generally, if you can turn the position tolerance off (if you are sure it has no effect) you should do it to reduce computational overhead.

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Alright. Thanks a lot.

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