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Geometry dependent upon variables

Posted 4 mag 2018, 02:40 GMT-4 Structural & Acoustics, Geometry, Parameters, Variables, & Functions Version 5.1 3 Replies

Khaled Harmouch
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Hello,

I have a 2D axisymetric Solid Mechanics simulation. I have a geometric boundary that changes with applied force. Can I make dependency between geometry and variables in Comsol?

Thank you in advance, Khaled HARMOUCH

3 Replies Last Post 14 mag 2018, 16:42 GMT-4
Josh Thomas Certified Consultant
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Posted: 7 years ago 4 mag 2018, 10:29 GMT-4
Updated: 7 years ago 4 mag 2018, 10:30 GMT-4

Khaled,

What is the physical mechanism that causes the boundary to change shape with applied force? Is it another object coming into contact? If so, you can solve the contact problem in COMSOL. If it is another mechanism (like Lorentz force from Electromagnetics), this can be applied as well.

Either way the deformation of the boundary under applied force is handled by the solid mechanics equations. The solver solves for the displacment field of all solid domains (including their boundaries). So, the dependency you are talking about is inherent in the formulation. No special dependency to define.

-------------------
Best regards,
Josh Thomas
AltaSim Technologies
Khaled, What is the physical mechanism that causes the boundary to change shape with applied force? Is it another object coming into contact? If so, you can solve the contact problem in COMSOL. If it is another mechanism (like Lorentz force from Electromagnetics), this can be applied as well. Either way the deformation of the boundary under applied force is handled by the solid mechanics equations. The solver solves for the displacment field of all solid domains (including their boundaries). So, the dependency you are talking about is inherent in the formulation. No special dependency to define.
Khaled Harmouch
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Posted: 7 years ago 14 mag 2018, 07:36 GMT-4

Hello Josh,

Thanks for your reply.

It's a contact problem. I have two flat objects in mechanical contact. One of them is vibrating. I am modelling the system in time domaine (time dependent study).

I can't use a contact boundary condition in comsol because I am simulating the roughness at the interface by a spring attached to each side of the objects in contact.

When comparing with experimental results, this simualtion works very good with low vibration amplitudes (negligible variation of contact surface with time). however, for high vibration amplitudes, the contact surface changes significantly with time and therefore must be represented in the simulation.

Therefore, I am asking if I can introduce the dependence between contact surface and contact force manually in the geometry section?

Thank you, Khaled

PS : sorry for the delay of my response, last week was a vacation periode here in France.

Hello Josh, Thanks for your reply. It's a contact problem. I have two flat objects in mechanical contact. One of them is vibrating. I am modelling the system in time domaine (time dependent study). I can't use a contact boundary condition in comsol because I am simulating the roughness at the interface by a spring attached to each side of the objects in contact. When comparing with experimental results, this simualtion works very good with low vibration amplitudes (negligible variation of contact surface with time). however, for high vibration amplitudes, the contact surface changes significantly with time and therefore must be represented in the simulation. Therefore, I am asking if I can introduce the dependence between contact surface and contact force manually in the geometry section? Thank you, Khaled PS : sorry for the delay of my response, last week was a vacation periode here in France.
Josh Thomas Certified Consultant
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Posted: 7 years ago 14 mag 2018, 16:42 GMT-4

Khaled-

Even if you are not using the contact algorithms built-in to COMSOL. As long as you are using "Geometric Non-linearity" (click on in the Step settings window under Study) then all surfaces should update shape with applied contact force during the simulation. This is inherent in the solid mechanics equations which solve for the displacement field of your geometry. I do not believe you can (or should) be updating anything in your geometry as a function of force.

Use the spatial frame (and read COMSOL documentation on spatial frame) to help understand and visualize the deformed shape of your system.

-Josh

-------------------
Best regards,
Josh Thomas
AltaSim Technologies
Khaled- Even if you are not using the contact algorithms built-in to COMSOL. As long as you are using "Geometric Non-linearity" (click on in the Step settings window under Study) then all surfaces should update shape with applied contact force during the simulation. This is inherent in the solid mechanics equations which solve for the displacement field of your geometry. I do not believe you can (or should) be updating anything in your geometry as a function of force. Use the spatial frame (and read COMSOL documentation on spatial frame) to help understand and visualize the deformed shape of your system. -Josh

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