7 Replies Latest reply on Aug 22, 2013 3:30 PM by Daniel Kitts

    Beam Contact Set FAIL

    Daniel Kitts

      Here's another issue I'm having with bonded contact sets and beams. 

       

      PROBLEM 1:

       

      I have the following model:

       

       

      Help_1.png

      And have created BONDED contact between the two SOLID bodies and a BONDED contact between BEAM structure/Solid face:

      Help_1a contact sets.png

      I'm trying to see my stresses in all beam components, for now just running gravity as the only external force and have the large cylindrical beam fixed on it's top joint (0 translation about X, Y, and Z, zero rotation about Y, Y is the UP direcion in these pictures) and fixture on bottom joint (0 translation in X and Z).

      Help_1b fixtures.png

      When I initially mesh this configuration, I get a huge gap between the two cylindrical beams at the left end of the truss structure (one beam is a full pipe, the other is a cut cylinder constrained to the face of the tube)

      Help_2 initial mesh problem.png

      How do I implement a contact here?  (Both of these are beam elements, so I cannot create a contact to either face)

       

      PROBLEM 2:

       

      Now, to try and get around the "gap" error above, I will treat the larger beam as a solid (now I'll have the ability to create a contact set to the face).  I updated the "Joint group", the component contacts, and updated the fixtures.  I created a new component contact between the large cylinder face and the cut cylindrical beam:

       

      Help_3 BasSol, contact.png

       

      I now must refine the mesh to handle the new solid component. I select a curvature based mesh and it handles the new geometry just fine:

      Help_4 BasSol, curvature mesh.pngHelp_4a BasSol, curvature mesh.png

      Everything looks peachy with the mest, the beam components (cut cylinder) appears to be contacted to the outer face of the large solid cylinder.

       

       

      However, once the simulation runs, the solution is messed up.  It seems that the interface between the beam and solid cylinder are not in place.  The stresses that are imposed on the beam frame do not translate into the solid cylinder.  From the displacement, it appears that the bottom beam actually penetrates the solid cylinder, but only near the bottom:

       

      Help_5 Solution is wrong.png

      I attached a video of the animated stress plot in the beam elements and an animation of the displacement plot (it's easy to see that the contact set between the beam and solid cylinder has no effect on stiffening the truss...it's as if the truss is only attached by the top joint). 

       

      Does anyone know why the bottom joint appears to be completely free and moving through the solid?

       

       

       

       

        • Re: Beam Contact Set FAIL
          Jared Conway

          problem 1, try merging the joints. otherwise you just might need to make one solids/shells and the other beams if you can't create the appropriate contact or add a component to connect them or use a connector. (there are still some limitations in the ability to connect things, the software is what you see is what you get, if it isn't there, you probably aren't missing anything, it probably just isn't available)

           

          problem 2, see your post here: https://forum.solidworks.com/thread/70983?tstart=0

           

          could be a software issue. i'd suggest isolating the problem in a simpler model to confirm whether the problem is software or setup/model related. connection between a solid or shell and a beam should be possible. may want to try standard vs curvature mesh. also try seeing if tightening up the gap helps.

            • Re: Beam Contact Set FAIL
              Daniel Kitts

              How do you merge the joints?

               

              I have greatly simplified the model, just looking at the cylinder and the cylindrical plate (both of these modeled as beams):  For some reason Solidworks won't even allow me to create a contact set or connect components....

               

              2BEAMS.png

              How do you merge joints in this case?

               

              Obviously for this case, it's easier to just analyze these components as solids.  But shouldn't we be able to do the same analysis for beams?

            • Re: Beam Contact Set FAIL
              Daniel Kitts

              So, I believe I figured out why it seemed the contact set between the cylindrical plate and the beam were being ignored:

               

              IT'S ALL ABOUT THE CONSTRAINTS

               

              The constraints shown above are not fixed in all direction, the fixture on the top cylindrical face is fixed in x, y, and z and no rotation about z, the bottom fixture constraint is fixed in the x and z direction.  These fixture types are utilized by means of the "Use Reference Geometry" option in the Advanced constraints.  The original reference geometry I was using was the face of an object parallel to the face of where I wanted to put the constraints.  Big No-No.  This it what allowed the beams to penetrate the large cylinder since the constraint reference was not on the large cylinder:

               

              Original constraint with reference geometry, allows beams to penetrate solid:

              3a. Reference constraint.png

              Correct referenced constraint shows solid moving with beams:

              3b. Reference constraint.png

               

              Although it is a very slight difference, it does show that when the correct constraints are in  place, the components move as one more smoothly....

              • Re: Beam Contact Set FAIL
                Jared Conway

                Can you post the model.

                 

                Changing the restraint reference shouldn't make contact work any different,

                  • Re: Beam Contact Set FAIL
                    Daniel Kitts

                    Ok, as I'm reevaluating these models, it looks like they both are not behaving correctly.  Looking at the displacment plots and animating the motion, the deformation is not being transfered to the constrained solid cylinder from the beam frame.  Both constraint types show that the frame is penetrating the solid cylinder.

                     

                     

                    So from this, does the reference geometry constraint type only control the direction that the constraint is (i.e. along the y-axis or no rotation about z)?  If that's the case than it only matters that your reference plane or face is parallel to where you constrain the model, correct?

                     

                     

                    See attached Zip folder

                         const a - reference on different face than constraint

                         const b -reference on same face as constraint

                  • Re: Beam Contact Set FAIL
                    Daniel Kitts

                    Here's another avenue I've gone down in the search for a solution to this problem.  This appears to provide reasonable results (until someone can counter this as inaccurate, wink, wink).

                     

                    I have treated the large cylinder and the cylindrical interface as Solids, while the truss is treated as a Beam.  Instead of mating the cut faces of the truss elements directly to the face of the cylindrical interface, I have instead constrained it by origin planes.  Then, I modified the Truss so the circular extrusion cut (23.25") is slightly larger than the diameter of the cylindrical interface (d = 23").  This creates a physical 1/8" gap between the truss and the interface (which allows spacing so Joints do not lay within a solid).  There are two more solid components mated to the beam truss as well, these also have a 1/8" gap.  (Basically, I included the gap between solids and beam elements that show the green Joint, representing a beam joint that is not connect to another structural member)

                     

                    Weld gap.png

                     

                    The curvature based meshed is used and when the model is ran in Simulation a notification pops up:

                    Weld gap solver error.png

                    All I think this warning is stating is that the solver automatically changes the meshing to handle the physical gap between components...

                     

                    The solution runs just fine after that and all the displacements as well as all the stresses seem to be correct.  Let me know if you have any responses/suggestions...

                     

                    Thanks!!