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thermal expansion leads to overlapping domains
Posted Oct 24, 2012, 6:25 p.m. EDT Structural Mechanics 3 Replies
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Hello!
I have a model composed of three layers, three different materials, of very different coefficients of thermal expansion. The top layer has cracks built into the geometry. The first two study steps model the deposition of the top two coatings. The third step heats up the entire structure. The domains initially separated by cracks now overlap. I would like to communicate to COMSOL that they should not overlap. How do I do that? I am using COMSOL 4.3. Physics include solid mechanics for steps 1 and 2, thermal stress for step 3, and heat transfer in porous media for steps 2 and 3.
Thank you!
Chelsea
I have a model composed of three layers, three different materials, of very different coefficients of thermal expansion. The top layer has cracks built into the geometry. The first two study steps model the deposition of the top two coatings. The third step heats up the entire structure. The domains initially separated by cracks now overlap. I would like to communicate to COMSOL that they should not overlap. How do I do that? I am using COMSOL 4.3. Physics include solid mechanics for steps 1 and 2, thermal stress for step 3, and heat transfer in porous media for steps 2 and 3.
Thank you!
Chelsea
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3 Replies Last Post Oct 24, 2012, 11:25 p.m. EDT
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Posted:
1 decade ago
Hello Chelsea,
That area of COMSOL modeling goes by the name of "Contact Pairs" or "Contact Modeling". Basically, you need to identify all the pairs of boundaries that might come into contact and then implement a very strong force that keeps them apart. COMSOL helps you out by providing the force.
Identifying the boundary pairs can be done in the model definitions, in the Model Builder menu selection "Model 1/Definitions/Pairs/Contact Pair". You can create one contact pair for each set of potentially interpenetrating boundaries in your model.
To implement the forces, you will use the selection "Solid Mechanics 2/Pairs/Contact". Then select the contact pair and specify any changes you need to the default force. (It is not called a "force" on this page, but a "penalty factor", but a rose by any other name smells the same.) Of course, accepting the defaults is a good place to start.
There is a lot of information about contact modeling in the help files, and they will help you out with suggestions for getting good results. In your case, the pairs are symmetric, so it won't matter which one of the pair you call the "source" and which you call the "destination". I suggest you try it out with just one of the cracks for starters, and then work from there. If you get stuck, check out the Model Library entries under "Structural Mechanics Module/Contact and Friction".
Good Luck!
That area of COMSOL modeling goes by the name of "Contact Pairs" or "Contact Modeling". Basically, you need to identify all the pairs of boundaries that might come into contact and then implement a very strong force that keeps them apart. COMSOL helps you out by providing the force.
Identifying the boundary pairs can be done in the model definitions, in the Model Builder menu selection "Model 1/Definitions/Pairs/Contact Pair". You can create one contact pair for each set of potentially interpenetrating boundaries in your model.
To implement the forces, you will use the selection "Solid Mechanics 2/Pairs/Contact". Then select the contact pair and specify any changes you need to the default force. (It is not called a "force" on this page, but a "penalty factor", but a rose by any other name smells the same.) Of course, accepting the defaults is a good place to start.
There is a lot of information about contact modeling in the help files, and they will help you out with suggestions for getting good results. In your case, the pairs are symmetric, so it won't matter which one of the pair you call the "source" and which you call the "destination". I suggest you try it out with just one of the cracks for starters, and then work from there. If you get stuck, check out the Model Library entries under "Structural Mechanics Module/Contact and Friction".
Good Luck!
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Posted:
1 decade ago
Thanks for the detailed reply! Much appreciated.
A quick follow up question... I created my contact pairs and can access them to apply a penalty force in my Solid Mechanics step. However, my study has multiple steps, and I can't seem to be able to access the contact pairs in the later physics. Of the three steps, the only step where the domains would potentially overlap (thermal stress). Here, when I select a contact pair, there is no list of pairs to choose from. Thoughts?
A quick follow up question... I created my contact pairs and can access them to apply a penalty force in my Solid Mechanics step. However, my study has multiple steps, and I can't seem to be able to access the contact pairs in the later physics. Of the three steps, the only step where the domains would potentially overlap (thermal stress). Here, when I select a contact pair, there is no list of pairs to choose from. Thoughts?
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Posted:
1 decade ago
Nevermind, got it!
Thanks
Thanks