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How to limit the deformation to contact surface

Posted May 22, 2015, 2:26 p.m. EDT Structural Mechanics 6 Replies

Qingbo Guo
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Hi Comsol,
I am doing a mechanical deformation simulation. My structure is mainly composed of two parts. The top part is made of glass. The bottom part is made of rubber with Young's modulus of 1.5MPa. There are thee saw tooth structure at the contact surface.
I want to study how does the saw tooth structure deform with certain applied load. I run solid mechanics simulation with boundary load applied on box 2 and fixed constraint applied on box1.

I expect the bottom saw tooth structure make contact with the top glass structure but it didn't. IT GO BEYOND THE CONTACT SURFACE (see Deformation.tif). My question is, how can I limit the saw tooth structure to make contact with the glass, as what should happen in real world, instead of go beyond the physical limit? The attached photo shows the deformation plot.

Thanks!




6 Replies Last Post Jul 6, 2016, 8:18 a.m. EDT
Qingbo Guo
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Posted: 9 years ago May 26, 2015, 4:53 p.m. EDT
anyone can give some suggestions?
anyone can give some suggestions?
Daniel Connelly
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Posted: 9 years ago May 27, 2015, 9:48 a.m. EDT
Okay, since nobody else responds, and I'm struggling with a similar issue, I'll do the best I can.

I think the issue is you want to ease the solution toward contact. That means doing a "continuation" approach, ramping a parameter which brings the surfaces into contact, rather than solving for the contact condition directly. The problem is the contact force is SO nonlinear that the system easily gets trapped and doesn't know how to escape. I also check the "nonlinear" option in the solution settings.

BTW, it's not so easy how to figure out how to do a continuation. It's not under parametric study, it's under stationary, under "Study Extensions". But you still provide a parameter ramp just the same. I like normalizing my ramps, for example if I'm applying a 3-d boundary force, I do "range(0, 0.05, 1) * 1e5[N/m^2]", rather than include the units directly in the range parameters. That makes it easier to scale the ramp, or even apply a nonlinear transform if I want the ramp step to be less at the beginning or end of the ramp.

Support can kick in and provide a better answer. I'm learning, as you are. So worth what you paid for ....
Okay, since nobody else responds, and I'm struggling with a similar issue, I'll do the best I can. I think the issue is you want to ease the solution toward contact. That means doing a "continuation" approach, ramping a parameter which brings the surfaces into contact, rather than solving for the contact condition directly. The problem is the contact force is SO nonlinear that the system easily gets trapped and doesn't know how to escape. I also check the "nonlinear" option in the solution settings. BTW, it's not so easy how to figure out how to do a continuation. It's not under parametric study, it's under stationary, under "Study Extensions". But you still provide a parameter ramp just the same. I like normalizing my ramps, for example if I'm applying a 3-d boundary force, I do "range(0, 0.05, 1) * 1e5[N/m^2]", rather than include the units directly in the range parameters. That makes it easier to scale the ramp, or even apply a nonlinear transform if I want the ramp step to be less at the beginning or end of the ramp. Support can kick in and provide a better answer. I'm learning, as you are. So worth what you paid for ....
Qingbo Guo
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Posted: 9 years ago May 27, 2015, 7:32 p.m. EDT
Daniel,
I appreciate your reply!
Are you saying a parameter sweep to find the contact point? I am actually looking for the contact area under different pressure level. That is to say, I need to know the contacting point as well as at even larger pressure, how much does it contact. And the problem right now is that, it penetrate the surface instead of making contact.

Any suggestions?

Thanks

Daniel, I appreciate your reply! Are you saying a parameter sweep to find the contact point? I am actually looking for the contact area under different pressure level. That is to say, I need to know the contacting point as well as at even larger pressure, how much does it contact. And the problem right now is that, it penetrate the surface instead of making contact. Any suggestions? Thanks
Max Mayer
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Posted: 9 years ago Jun 4, 2015, 4:14 p.m. EDT
Hello Quingbo,

I have the same problem.
Sadly I don't have an answer.
Did you find an solution and can tell me how do fix the problem?
Maybe somone else can help me/us.
Hello Quingbo, I have the same problem. Sadly I don't have an answer. Did you find an solution and can tell me how do fix the problem? Maybe somone else can help me/us.
Jeff Hiller COMSOL Employee

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Posted: 9 years ago Jun 5, 2015, 8:10 a.m. EDT
Hello Qingbo,
The model in your file is not set up as a contact problem.
For an introduction on contact modeling, read the Structural Mechanics Module's User's Guide, version 5.1, page 121 and following.
Best,
Jeff
Hello Qingbo, The model in your file is not set up as a contact problem. For an introduction on contact modeling, read the Structural Mechanics Module's User's Guide, version 5.1, page 121 and following. Best, Jeff
Vivek K
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Posted: 8 years ago Jul 6, 2016, 8:18 a.m. EDT
Hi friends,
I also having the problem of deformation above the physical limit. In my geometry there are 3 layers. The first one is an epoxy layer, Middle one is a glass fiberand the third layer is again the same epoxy material. While a mechanical load is applying on the outer layers , each domain moves beyond the physical limit. Please see the attached image. How Can I solve this issue.

Please send your valuable suggestions
Hi friends, I also having the problem of deformation above the physical limit. In my geometry there are 3 layers. The first one is an epoxy layer, Middle one is a glass fiberand the third layer is again the same epoxy material. While a mechanical load is applying on the outer layers , each domain moves beyond the physical limit. Please see the attached image. How Can I solve this issue. Please send your valuable suggestions

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