4 Replies Latest reply on Mar 22, 2018 2:01 PM by Don Weber

    Unconstrained bodies in multibody part.

    Don Weber

      I have a mulibody part made from converted bodies. I can't convince Solidworks that these bodies should be bonded together, even when I tell it they are bonded. Hence I can't run a simulation.


      I am also having issues with Solidworks telling me to define a material even though all materials are defined.


      I am running 2018. Should have never upgraded.

        • Re: Unconstrained bodies in multibody part.
          Ryan Dark

          Hi Don,

          This is a common question that comes up a lot on this forum.  The model is definitely unstable but tracking down how it is unstable is the real problem.  I went through a quick stability diagnosis in a duplicate of your study like this:


          1. Go into the study 'Properties'

                    Turn on 'Use soft springs to stabilize model'

                    Turn off 'Compute free body forces'

                    Turn off 'Large displacement mode'

          2. Suppress all loads and apply only 'Gravity'

          3. Mesh/Run the study

          4. When the solver stops (if it stops) due to large displacements and prompts to put the study into 'Large Displacement mode' declined this offer.  The solver will dump what results it has so far

          5. Inspect the displacement plot in the results to find the unrestrained body


          For any body that is unconstrained you would need to create explicit 'Contact Sets' in order to bond these unrestrained bodies to the rest of your structure.


          This video (GoEngineer - Simulation: Common Errors in Simulation Webinar) and this document (GoEngineer - Simulation: Diagnose Unstable Studies) give more detail study instability.