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Thermal Stress and Heat transfer in an Assembly. Contact boundaries don't seem to work.
Posted Jun 20, 2019, 3:37 a.m. EDT Structural Mechanics Version 5.4 1 Reply
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Dear All,
I wonder wether or not someone can help me with a simple problem. At least that is what I assume.
I am working on thermal stress in a cooled mold and wonder about the heat transfer when the molded part looses contact with the mold wall due to shrinkage.
Hence, I use an assembly in a simple geometry, which is a rectangular region representing the mold and a smaller rectangle within the larger one to represent the molded part.
The molded part is initially at 300°C and the mold at 130°C. I set-up everything with the appropriate boundary conditions and material parameters. As contact model I use the pnealty method and standard settings for the Pair thermal contact. In the Solid Mechanics Module I apply gravity for the molded part so when it shrinks due to cooling, it will "fall" on the mold wall where the contact boundary should detect the contact. In that way, at least that is what i thought, there is always a contact between molded part and mold wall. However, the molded part moves right through the contact boundary and also there is no heat transfer at all.
I really wonder what is happening there. I am not a solid mechanics specialist at all, but from my understandig I set-up everything correctly. Maybe there settings that I need to tweak or I really did something wrong in setting-up the problem.
So if any of you are working or worked on similar problems, maybe you can give me some advice. Anything you can tell me is greatly appreciated.
Best regards, André
PS: I attached the model file I am using. PPS: Also, before you ask. On advice of Henrik I already read the manual on the topic of contact modeling. Especially when it comes to meshing and choosing source and destination in the contact pair.
Attachments:
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Hello fellow COMSOL'ers,
I worked a little more on my problem and figured out two things:
1) I guess the molded geometry is not "falling through" the mold. It is just a question of scaling. When I set the scale parameter in the deformed geometry to 1, it seems alright. However, it still seems to be falling through the mold, but I guess this is due to high contact forces.
2) The second point is with respect to the mesh. The of the molded part are fillets with a small radius. I somewhere read that this is preferrable over sharp edges which would form singularities. However, it doesn't matter how fine I resolve the edges/fillets they always are distorted right from the beginning of the simulation run.
Is there anybody who faced the same problem and could share some advice on how to resolve this issue. I'd greatly appreciate it.
Best regards, André.