body in simulation considered "Free" though "separation" is applied

[melfio]

So I have a body that will have one force applied in the Z axis, nothing more. It is contained in the YZ plane and part of the XZ plane, as far as I can tell (Contacts are set to "separate" for the cylinders and the holes).The DOF view says it is free and simulation shows no deformation or stress on the body from the force, I made a simple test that I believe has the same basic setup and the test works, I don't see the difference..

 Intended simulation:

Simplified problem that works, I don't see why the other one doesn't..:

[melfio]

So I have a body that will have one force applied in the Z axis, nothing more. It is contained in the YZ plane and part of the XZ plane, as far as I can tell (Contacts are set to "separate" for the cylinders and the holes).The DOF view says it is free and simulation shows no deformation or stress on the body from the force, I made a simple test that I believe has the same basic setup and the test works, I don't see the difference..

 Intended simulation:

Simplified problem that works, I don't see why the other one doesn't..:

[lichtzeichenanlage]

I guess you've used the automatic contact finder. The pins of the red part are way smaller than the holes in the green part and the solver couldn't find a contact area for them with de default 0.1mm setup. You could either change this default to a larger value but it would be better to add manual contacts by using Contacts -> Manual Contacts

[lichtzeichenanlage]

I guess you've used the automatic contact finder. The pins of the red part are way smaller than the holes in the green part and the solver couldn't find a contact area for them with de default 0.1mm setup. You could either change this default to a larger value but it would be better to add manual contacts by using Contacts -> Manual Contacts

[melfio]

Contacts are set to "separation" for each cylinders and corresponding hole. I  have updated the post as well.

[melfio]

Contacts are set to "separation" for each cylinders and corresponding hole. I  have updated the post as well.

[John_Holtz]

Hi @lichtzeichenanlage

Technically, the one part is "free" because of the following:

1. It looks like there is nothing to prevent free motion in the X direction.
2. The software does not know if the separation contact will hold it in the Y direction until the analysis is complete.
3. The software does not know if the separation contact will hold it in the Z direction until the analysis is complete.

I do not see any mention about what type of analysis you are running. Linear static stress and nonlinear static stress should not be able to calculate the results when there is a large gap between parts. You can think of it like this: you apply a force of X to the free part (it's free because there is a big gap). Because it is not in contact with anything, how far does it move? (The answer is that it moves an infinite distance -- mathematically.)

If you are going to use a static analysis, these are the things you should do to improve the analysis:

1. Add a constraint so that it cannot move in the X direction.
2. Possibly add a constraint so that it cannot move in the Y direction.
3. Move the free part so that it is initially touching the other part.

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[John_Holtz]

Hi @lichtzeichenanlage

Technically, the one part is "free" because of the following:

1. It looks like there is nothing to prevent free motion in the X direction.
2. The software does not know if the separation contact will hold it in the Y direction until the analysis is complete.
3. The software does not know if the separation contact will hold it in the Z direction until the analysis is complete.

I do not see any mention about what type of analysis you are running. Linear static stress and nonlinear static stress should not be able to calculate the results when there is a large gap between parts. You can think of it like this: you apply a force of X to the free part (it's free because there is a big gap). Because it is not in contact with anything, how far does it move? (The answer is that it moves an infinite distance -- mathematically.)

If you are going to use a static analysis, these are the things you should do to improve the analysis:

1. Add a constraint so that it cannot move in the X direction.
2. Possibly add a constraint so that it cannot move in the Y direction.
3. Move the free part so that it is initially touching the other part.

______________________________________________________________

If my post answers your question, please click the "Accept as Solution" button. This helps everyone find answers more quickly!