6 Replies Latest reply on Jun 22, 2015 2:36 AM by Nandish Datti

    Why does my model have joint failure?

    Vagulus Dagg

      I have a weldment

      2015-06-17_17-15-08-Pretty_Balls.png

      for which SWX calculates the joints okay, meshes okay, but fails when tested.

      2015-06-17_13-11-15-Model_Unstable.png

      I tried doing a Frequency Test after watching a video on checking weldment joints but my computer can't count

      2015-06-17_13-19-52-Solver_Difficulty.png

       

      I have visually checked the joints and they all seem to be mated properly.  I am really at a loss.  Could it be a problem with the Profile Locations?  Most of the members are not aligned with the longitudnal (is that the neutral) axis.

       

      Can someone tell me why the tests fail, or perhaps give me some keywords or point me at a tutorial on solving this problem.

      Thanks.

        • Re: Why does my model have joint failure?
          Attilio Colangelo

          The model is severely disjointed.  Any place you see multiple purple dots at a junction indicates the members are not connected at that location.

           

          Why is this happening?  Comparing a similar model I made the key difference is you need to use a single "continuous" 3D sketch.  Your multiple 2D sketches breaks the joint where the sketches meet.  I believe there is a beam model in the tutorials you can open and inspect to see how weldments should be connected.

            • Re: Why does my model have joint failure?
              Vagulus Dagg

              Thanks Attilio

               

              You are not quite right about the purple dots.  Multiple purple dots, in this case, correctly reference the joints between the diagonal brace and the upper and lower struts.

              As far ad the 2D-3D debate goes, several tutorials I have referenced show modelling in 3D using several contiguous 2D sketches.  The trick appears to be to use Convert Entities tobring lines from one sketch into the other so they can connect.  It's working for me anyway, and I find it easier working with planes and 2D sketches than juggling with the alignment of 3D lines.  I guess that is a matter of preference.

               

              However, you are right about the disjointed bit.  Here I have found the key to be ensuring the the member to be trimmed is completely mated to the trimming member.  When I corrected a couple of joints at the front end the whole thing started to work.

            • Re: Why does my model have joint failure?
              Nandish Datti

              There are end caps in your model which are treated as solid bodies.

              You will have to define bonded contact between the beam end joint and the solid body face.

              To accurately consider small clearance between the end caps and the beam, select the 'less than' radio button in the 'Edit Joints' property manager and recalculate all the joints. Then define the bonded contact between the solid body face and the joint representing the free end of the beam(Yellow color spheres).

              you should be able to run the study without any issues.

              Edit Joints.pngfrequency.png

                • Re: Why does my model have joint failure?
                  Vagulus Dagg

                  I get somewhat better results when I try your idea of defining acceptable clearances, but I am still not quite there yet.

                   

                  You advise, "You will have to define bonded contact between the beam end joint and the solid body face."  Please, how do I do that?  I seem to go through the motions, or what I think are the motions, but I do not get bonded contacts.  I must be doing something wrong.  Would you please, tell me how to get it right.

                   

                  Thanks

                    • Re: Why does my model have joint failure?
                      Nandish Datti

                      The bonded contact should be defined between the solid end caps and the end joint of the beam. When you recalculate the Joints considering the minimum clearance you will see eight yellow spheres(beam joints) in your model and they represent the end of the beams. The pink color sphere represent beam to beam connection.

                      To define the bonded contact in the Contact Sets property manager set the contact set type to bonded then select beam joint (Yellow color) in selection set 1 and the end cap face in the selection set 2. Follow the same procedure for all 8 beams joints. This ensures that the end caps are properly welded to the beams.

                      Refer the attached image.Bonded contact.png