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Comsol problem

  1. Sep 30, 2008 #1
    hi guys,
    i am having a problem with comsol.
    i want to simulate what force is needed to tilt for example a table on the floor.
    althought there is a problem in my drawing i think, because if i enter the solve mode you can see the floor actually pulls the table back on the floor when it actually should tilt. the table and the floor just wont seperate.
    how to solve this?
    any idea is welcome :)

    tnx in advance
  2. jcsd
  3. Oct 2, 2008 #2


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    hi Ant01,

    could you elaborate a bit what you've actually done? What application mode you've selected and how you've constructed your model so far (I'm thinking how you enable the movement and such in the 1st place, how have you defined the initial situation, separated the floor & table, enforce the contact between them etc.). This sounds quite a bit like simulating mechanisms, not something have seen done lot in Comsol, but nothing prevents one from doing such an analysis for sure.
  4. Oct 2, 2008 #3
    hi PerennialII,

    I've used the Plane Strain mode from the Structural Mechanics Module.
    The table and the floor are 2 different objects, although they both use the same boundary where the feet of the table meets the floor. In the point settings I've put a load of -30 N on the edge of the table. If I enlarge the deformation by lets say 100 i see the floor coming up at the feet of the table (from the opposite site from where I've set the load).
    I think its going wrong because they both use a same boundary, but I dont know how to fix this.

    Tnx for the reply :)
    Last edited: Oct 2, 2008
  5. Oct 3, 2008 #4


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    Yeah, that boundary is the difficult aspect of it. Both objects should have separate boundaries, and then you should enforce a 'contact condition' between these objects (the boundaries). Then the analysis tracks their relative positions during the tilting of the table and doesn't permit them penetrating each other (within a tolerance) but rather creates contact pressure and stresses to the bodies as a result of the contact. If you're running a fairly late version of Comsol (3.3, 3.4 at least) there is a direct option of defining contact between bodies which might be handy (meant specially for the structural mech module presume). Initially you can define the floor & table to have that boundary either at identical coordinates or define a small gap between them which you then close at the beginning of the analysis (so called adjustment step often done in contact analyses, sometimes easier to do this way rather than have different objects at a zero distance from each other at the start of the analysis).
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