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ANSYS Static Structural boundary constraints issues

  1. May 30, 2012 #1
    Hey all,

    First off, I'd like to mention that I am completely unfamiliar with this ANSYS and have been fighting with this program for last 2 and half weeks. Any feedback and help is greatly appreciated! Please refer to the photos attached for referral.

    My project currently involves analyzing the stresses and deformation occuring on the gripping blocks as well as the piece of pipe. Basically what i'm trying to model is a piece of pipe being clamped by two blocks. The blocks have a profile on them that grip the pipe. The pipe is clamped by equal and opposite forces being applied on each block.

    Under connections->contacts, I have frictionless contacts between the face of the pipe (target) and the profile of the gripping blocks (contact).

    As for meshing, I'm currently just doing a very coarse test to see if the analysis works. I'm not sure if this is a good method but to save time I am doing this method for now.

    I have forces applied onto the blocks as well as frictionless supports for where I cut it in half (due to symmetry)


    My problem is that when I solve for it, the blocks vanish as if its not there. I hope this is a simple fix and i'm just missing something very simple.


    I apologize if I missed out on a lot of crucial information. Please feel free to ask anything I may have missed out on that would aid in my situation and I will respond ASAP.
     

    Attached Files:

    Last edited: May 30, 2012
  2. jcsd
  3. May 31, 2012 #2
    If the mesh for the contact interface is course then Ansys might not recognise the components and hence will fly off into space.
    Also if the contact is initially closed but there is a large gap between the mating components then the components will pass through each other. Check your contact settings.
    SO consider refining the mesh
     
  4. May 31, 2012 #3

    AlephZero

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    If your model is geometrically "perfect" and the contacts are all frictionless, then the pipe can slide out of the blocks and rotate about its axis inside the blocks. The two blocks can probably slide around relative to each other as well.

    You need to apply some restraints to stop things like that from happening.

    If you set up the model correctly, you will get no reaction forces at these additional restraints, so they won't affect the results.

    You can use ideas about symmetry to choose the restraints. For example the plane cutting the length of the pipe into two halves will not move along the length of the pipe (by symmetry, there is no reason why it should move in one direction rather than in the opposite direction) and it won't rotate about the axis of the pipe.
     
  5. May 31, 2012 #4
    Thank you Bugatti and AlephZero for your help. I will go ahead right now and solve for it using my full mesh count. I've refined it using size meshing on the blocks profile as well as the face of the pipe. Element size is at 0.0155 inch.

    As for the restraints you suggested Aleph, I'm not entierly sure what else I can do. I've played around with the settings and all that for more than a week no to no avail. Will keep trying different things though!
     
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