General Mechanical

General Mechanical

Multibody part + Nonlinear contacts

    • mboniface91
      Subscriber

      Hello everyone,


      Is it right to use multibody part on geometries of different parts (i.e. all parts combined in one multibody part) which are not actually from the same part and initially are not touching, then in mechanical, applying nonlinear contacts like frictionless or frictional contact on the same multibody part? I want to verify how right this is and kindly give me an explanation w.r.t. your reply. Thanks in advance.

    • Sandeep Medikonda
      Ansys Employee

      Hi, It is so hard to suggest anything without any pictures...Please use the inline image option to illustrate what you are dealing with and the goal of your study?


      When you use multibody part, the bodies are grouped together but no sharing takes place. So you might want to use shared topology if they are touching and connections if they aren't? See here.


      Regards,
      Sandeep


       

    • peteroznewman
      Subscriber

       It is not ideal to have multiple bodies in a single part that you want to define some connection between those bodies, either joints or contacts. The reason is the Body Views functionality that pops open two windows, one for the Target side of the connection and another for the Contact side of the connection. This functionality will be broken if you are defining connections between bodies in the same multibody part.  If you are in DesignModeler, there is the Explode Part function that can separate each body into its own part. This is what I do when my NX CAD system provides geometry using the Plug-in to DesignModeler.


      However, if you don't Explode the Part to separate the bodies, you can still define connections, but the Body Views windows will be useless since all the bodies in the part will show up in both windows. They should really call it Part Views, not Body Views.


      Regards,
      Peter

    • mboniface91
      Subscriber

      Thanks Peter for your reply. Will breaking the body views window affect the fidelity of the result?


      Regards,


      Michael.


       

    • peteroznewman
      Subscriber

      Michael,


      Having no Body Views just affects your productivity at creating and verifying connections. It has no effect on the solving or results processing.


      Regards,
      Peter

    • Montassar
      Subscriber
      Hi peteroznewman,nI am actually using the multibody parts to create a mesh with variable methods, this is useful for linking the nodes between bodies.nnMy question is: if we use this method to connect different parts, this will make constraints to much the contact surfaces, and therefore generate more nodes which means more computational time, right?.
    • peteroznewman
      Subscriber
      ,you say different parts, but do you mean parts or do you mean bodies? In DM, you can have a multibody part. The bodies in that part share topology and so in Meshing, there are common shared nodes on the coincident faces. In DM, if you have two parts, you don't share topology and the nodes are not shared. You would do that if you wanted Frictional contact between the parts. nIf you use Bonded Contact between parts instead of Shared Nodes to connect two bodies, the contact elements do add a little overhead to the computation, but not a huge amount.n
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