3 Replies Latest reply on Apr 19, 2017 1:41 PM by Ryan Navarro

    Manually modelling bearings in Large Displacement Simulation

    Nicholas Arthur

      I'm currently trying to figure out a way to manually recreate the Solidworks Bearing Connector functionality for use in a Large Displacement Simulation, in Solidworks 2015. In general terms, the assembly comprises a number of beams of rectangular section, which are joined with pins and bearings, one at the top and one at the bottom, at each end. Unfortunately I cannot give any more specific details due to confidentiality issues.

       

      With regards to meshing, I eventually plan to use a mixed mesh comprising a beam element in the centre, and solid mesh at ends to mesh more complex solid features. For the time being I can get useable results using a solid mesh throughout for simplicity.

       

      The bearings in question are spherical rollers. In particular I wish to allow free axial movement of the upper bearing (by using 0 axial stiffness in the bearing connector dialog) such that the lower bearing takes all the axial load. I have tried using 'on cylindrical face' constraints with a bonded shell to solid mesh, in order to constrain translations and allow the appropriate number of rotations about each axis. The problem is that 'on cylindrical face' or 'on spherical face' seem to constrain faces relative to the global coordinate system. What I would really like to do is constrain two surfaces relative to each other, as with a 'real life' bearing, but allow the whole bearing itself to move globally as the beam(s) deform.

       

      I have read the kb article on the actual formulation used for bearing connectors, but I don't see how I can practically recreate this using the available tools in simulation. Am I asking too much of Solidworks?

        • Re: Manually modelling bearings in Large Displacement Simulation
          Ryan Navarro

          I would recommend investigating using  "Remote Load/Mass" in the "Displacement" mode. When used in this way it allows selectively removing degrees of freedom about a local coordinate system.

           

          You can see an example I posted at the bottom of this thread (in this case I was suggesting it more as a fixture but it could also be used as a bearing)

          https://forum.solidworks.com/message/730223#comment-730223

            • Re: Manually modelling bearings in Large Displacement Simulation
              Nicholas Arthur

              Thanks for taking the time to reply - I've taken a look at the post, but unfortunately can't open the file as I'm still using 2015.

              I'm probably missing something, but doesn't using a remote displacement require you input a displacement in the 'free' direction?

               

              Restricting the translation of the outer race only in the radial directions about the L.C.S. seems to be insufficient; I get a large displacement and incorrect solution. Adding the inner race (which is already constrained to it's housing) removes the large displacement, but over constrains the model as some axial force is taken out by top bearing with the remote displacement. I checked this by running a known 'good' model using bearing connectors and listing the connector force.

               

              I think a key point is that the housings of each bearing cannot be treated as ground, as the surrounding structure is also expected to deform and/or move from it's original position.

                • Re: Manually modelling bearings in Large Displacement Simulation
                  Ryan Navarro

                  If you could upload an annotated screenshot or at least hand sketch, I think then more people might be able to chime in

                   

                  From your original post:

                  "What I would really like to do is constrain two surfaces relative to each other" -
                  you could do this bonding across gap (local contact bonding) or using spring connectors or rigid link. Spring connectors may be a good solution as they would let you input radial and axial stiffness. Small amount of axial stiffness might help solution stability

                   

                  "doesn't using a remote displacement require you input a displacement in the 'free' direction" -
                  Not necessarily. If you leave the checkbox cleared for that DOF then it won't be restrained. But you may need to otherwise stabilize the solution somehow as you saw with the large displacement warning.

                   

                  Maybe it is the type of problem where you might need to "Use Soft Springs" to stabilize solution (option in study properties)

                  Again a simple sketch would go a long way to help others interpret your problem