Discussion Forum

You might try the 'Rigid Connector' features.

You might try the 'Rigid Connector' features.

Dear Edgar J.Kaiser,

Thank you for your help. But I didnot get the point. Can you tell me more details? How to set the Rigid Connector features?

Thank you sinerely.

You can apply rigid connector boundary conditions in 3D to boundaries, edges and points. As the name says they can rigidly tie parts of your model together, such as the connecting edges of your helix. I suggest you check the details of these features in the documentation. This will allow you to assess whether rigid connectors are what you need. And you can try them.

You can apply rigid connector boundary conditions in 3D to boundaries, edges and points. As the name says they can rigidly tie parts of your model together, such as the connecting edges of your helix. I suggest you check the details of these features in the documentation. This will allow you to assess whether rigid connectors are what you need. And you can try them.

Dear Edgar J.Kaiser,

Thank you for your help. But I only find the Rigid connector in boundaries . And I could not choose the edges that need to be connected. Furthermore, for the Helix structure, the contours do not always follow the tangent line of the threads. Can you show me an example for solving this problem? Here is an image for the problem that I mentioned above. https://www.dropbox.com/s/lz353iqkfsbj2ci/rigid%20connector.png?dl=0

Thank you sinerely.

Hi,

Rigid Connector on edges and points were introduced in version 5.4. So if you are running an older version you will only see the boundary selection.

As to the original question, I think you need to explain more in detail (maybe with a sketch) which deformations that you allow and not. To me, it seems more like a contact problem.

Regards, Henrik

Hi,

Rigid Connector on edges and points were introduced in version 5.4. So if you are running an older version you will only see the boundary selection.

As to the original question, I think you need to explain more in detail (maybe with a sketch) which deformations that you allow and not. To me, it seems more like a contact problem.

Regards, Henrik

Dear Henrik,

Thank you for your help. you could see from the image. the relative displacement of the threads are not accpected. There is not any gap between every two threads. The thread 1 and thread 2 should adhesive each other totally. (also for other threads.) I should not see the part 3 after the simulation.( the elongation part). I think it is a contact problem. But I don't know how to adhesive the threads together. And I do not have version 5.4 for Comsol.

https://www.dropbox.com/s/wp1amw076z7f12h/sketch.png?dl=0

Thank you sincerely.

Best regards,

Jie Mao

You may also consider to design the helix with a small overlap of the windings. This would tie the windings together as well. The allowed degree of approximation depends on your primary question to the model.

You may also consider to design the helix with a small overlap of the windings. This would tie the windings together as well. The allowed degree of approximation depends on your primary question to the model.

Dear Edgar J. Kaiser,

I tried this method already. It did not work. The software still think they are not bonded together although I overlaped the threads.

Best regards,

Jie Mao

Jie Mao,

I was surprised that the overlap doesn't work. Obviously Comsol doesn't want to connect boundaries of objects overlapping themselves. Also the meshing seems to be tedious.

I got curious and tried something different. I introduce a second smaller helix running between the threads of the first one. It acts as something like a soldering bond. You may want to modify that to your needs. I attach an example in Comsol 5.3. Just execute the geometry tree step by step to learn how it works. Solve the model and you see that you have a union between the helix threads and the 'solder'.

The procedure may look cumbersome but is probably more physical than something like a rigid edge connector.

Good luck Edgar

Jie Mao,

I was surprised that the overlap doesn't work. Obviously Comsol doesn't want to connect boundaries of objects overlapping themselves. Also the meshing seems to be tedious.

I got curious and tried something different. I introduce a second smaller helix running between the threads of the first one. It acts as something like a soldering bond. You may want to modify that to your needs. I attach an example in Comsol 5.3. Just execute the geometry tree step by step to learn how it works. Solve the model and you see that you have a union between the helix threads and the 'solder'.

The procedure may look cumbersome but is probably more physical than something like a rigid edge connector.

Good luck Edgar

Dear Edgar,

Thank you very much.

I also tried this method. But it was hard to mesh. Here a are lots of warnings also in your program, which makes it hard to do the simulation.

Tips: In your model, the number of turns of Helix 2 could be number of turns of Helix 1 substract one, so that you do not need to delete entities.

In my system, I want to do a electromechanical simulation. The image is the side view of the model. It is a core-shell-shell structure. The high voltage potential is applied on the edges of the core. And use fixed constraint for one end of the Helix. Could you please try to do a simulation of this structure? I find mesh is very difficult for this structure. I use swept for mesh if there isn't an additional helix for soldering. However, if we add the additional helix, it shows me a lot of errors. So, how to solve this problem?

Thank you sincerely,

Best,

Jie Mao

Yes you need to set up a user controlled mesh for that. But I think this can be done. It was meant to be a hint. I won't be able to afford more time for the detail work on this.

Good luck Edgar