6 Replies Latest reply on May 11, 2017 1:56 PM by Durval Nascimento

    Underconstrained bodies error.

    Michael Wardas

      I'm new to Solid Works and to Simulation in particular and am struggling with correcting the error I'm getting (See attachment). I'm tried running the underconstrained bodies tool and found items that are free moving but thought they were 'bonded' via the contact set that I used.

      I've attached the zipped model.

      Any help would be appreciated.

      Thanks in advance!

        • Re: Underconstrained bodies error.
          Keith Frankie

          You don't have a material assigned to some of the bodies (specifically the ones that are set to rigid).  My guess is that SW is choking on the gravity force to apply.


          I'd call this a bug; rigid bodies without material assignment seem to work fine if gravity is not invoked, but create odd errors with the gravity load included.  Usually SW throws a warning if a material isn't assigned, but it seems to skip this if the offending body is rigid.


          As with all simulation studies that are having trouble the best bet is to remove all bodies except the ones at the fixture, then add them back in slowly till you show the error.  This lets you narrow down the error to one particular body.

            • Re: Underconstrained bodies error.
              Michael Wardas

              Hi Keith,

              Thanks for looking at this for me. However when I added material to the rigid parts I still get the same error.  I tried suppressing the gravity force but that doesn't help either.

              Were you able to fix my simulation so it works?

                • Re: Underconstrained bodies error.
                  Keith Frankie

                  Yes, I can get it to run.  There's the lack of material assignment issue (which SW treats oddly) and two other issues:


                  -There's one place where you incorrectly define the contact between a shell and a solid.  When you're defining contact to a shell you have to reference geometry on the shell.


                  -One of your parts is straight up missing any contact condition, so it's free to fly off into the ether.


                  To find these two issues suppress everything "above" the weldment, confirm that runs, then "include" parts back into the analysis one by one.


                  While you're troubleshooting you can get by with a much coarser mesh.  Drag that mesh slider all the way to coarse.

              • Re: Underconstrained bodies error.
                Dan Golthing

                Sometimes the assumed constraints don't work.  I've seen on occasion the need to add a constraint that should have been automatic.


                Can you run a frequency analysis to see if something is moving that isn't supposed to?  And what Keith said, make sure to apply materials.

                • Re: Underconstrained bodies error.
                  Durval Nascimento

                  Could you talk me what do pretend to verify with this analysis?