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boundary integration in podtprocessing

Posted 10 mars 2010, 11:14 UTC−5 4 Replies

Alex Zinchenko
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Dear all,

I have a simple question about comression simulation.

I have a cube in mechanical module.
I applied a prescribed displacement(in -y direction)as a boundary settings for upper boundary.
bottom boundary is fixed.

In Postprocessing/boundary integration I clicked on upper boundary and chose reaction force in y direction.

This reaction force has negative value!!!!!!!

How it can be that I press on cube and cube's reaction force is negative?

Thanks in advance,
Alex
4 Replies Last Post 11 août 2010, 02:26 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 14 mars 2010, 13:24 UTC−4
Hi

I would expect that the reaction force sign is defined with respect to the surface normal = direction pointing "outwards" of the volume.

Therefore I find the signs rather coherent that way, but I agree it's a convention issue

Do you agree ?

Good luck
Ivar
Hi I would expect that the reaction force sign is defined with respect to the surface normal = direction pointing "outwards" of the volume. Therefore I find the signs rather coherent that way, but I agree it's a convention issue Do you agree ? Good luck Ivar
Alex Zinchenko
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Posted: 1 decade ago 15 mars 2010, 06:18 UTC−4
Hi Ivar,

of course it is but the problem is that in my case it works only in x and z directions.
It should be that reaction force directed according axes but this rule works only in x and z directions...
in y direction(where my prescribed displacement applied) it works in opposite way...

Thank you in advance,
Alex
Hi Ivar, of course it is but the problem is that in my case it works only in x and z directions. It should be that reaction force directed according axes but this rule works only in x and z directions... in y direction(where my prescribed displacement applied) it works in opposite way... Thank you in advance, Alex
Joe Xiao
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Posted: 1 decade ago 10 août 2010, 17:14 UTC−4
Hi Alex:

I am having a similar issue, I was wondering if you can help me. I am modeling the insertion of a probe into the a cube. The probe I am having in post processing is that using point evaluation on vertices or boundary integration on the probe boundaries, the reaction force is always zero (in the z-direction of insertion).

I am looking for the resistance force that the probe is experiencing during the insertion - this is the reaction force right?
Also, for those points on the surface of the cube that are not part of the geometry, I cannot do point evaluation of any parameters on those points, any idea why?

I am attaching a simple version of this simulation.

Thank you,

Joe
Hi Alex: I am having a similar issue, I was wondering if you can help me. I am modeling the insertion of a probe into the a cube. The probe I am having in post processing is that using point evaluation on vertices or boundary integration on the probe boundaries, the reaction force is always zero (in the z-direction of insertion). I am looking for the resistance force that the probe is experiencing during the insertion - this is the reaction force right? Also, for those points on the surface of the cube that are not part of the geometry, I cannot do point evaluation of any parameters on those points, any idea why? I am attaching a simple version of this simulation. Thank you, Joe

Attachments:

Joe Xiao
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Posted: 1 decade ago 11 août 2010, 02:26 UTC−4
Hi Ivar:

I am having a similar issue, I was wondering if you can help me. I am modeling the insertion of a probe into the a cube. The probe I am having in post processing is that using point evaluation on vertices or boundary integration on the probe boundaries, the reaction force is always zero (in the z-direction of insertion).

I am looking for the resistance force that the probe is experiencing during the insertion - this is the reaction force right?
Also, for those points on the surface of the cube that are not part of the geometry, I cannot do point evaluation of any parameters on those points, any idea why?

I am attaching a simple version of this simulation.

Thank you,

Joe

Hi Ivar: I am having a similar issue, I was wondering if you can help me. I am modeling the insertion of a probe into the a cube. The probe I am having in post processing is that using point evaluation on vertices or boundary integration on the probe boundaries, the reaction force is always zero (in the z-direction of insertion). I am looking for the resistance force that the probe is experiencing during the insertion - this is the reaction force right? Also, for those points on the surface of the cube that are not part of the geometry, I cannot do point evaluation of any parameters on those points, any idea why? I am attaching a simple version of this simulation. Thank you, Joe

Attachments:

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