2 Replies Latest reply on Jun 26, 2012 2:30 PM by Mikael Martinsson

    Different displacement result, beam, surface and solid

    Mikael Martinsson

      Hi.

      I made 3 static studies on a ladder shaped part. One with beam elements, one with surfaces and one with solids.

      The surface and solid version gives similar displacement results.

      The one with beam elements gives a larger deformation.

       

      The "ladder" is made with VKR tubes 50x30x3,2 mm (steel 210Gpa)

      Length 5000 mm

      Width 500 mm

       

      2 simple fixtures ("fixed" and "on flat surface" and 1 load of 750N

      Bonded contact between the parts.

      Done in SW2012 SP2.0

       

      The resulting deflection (UY):

      Beam: -106 mm

      Surface: - 79 mm

      Solid: -76 mm

       

      Pictures on beam and solid versions are attached.

      What did I do wrong with the beams setup?

        • Re: Different displacement result, beam, surface and solid
          Chris Fernald

          Not sure about this, but one possiblity could be the fact that the solids are restrained on faces, and the beams are restrained on joints.  If the restrained faces are sufficiently large, they will react some of the bending moment caused by the load.  Beam joints, on the other hand, are points that are free to rotate. This may be allowing them to pivot more freely, giving you more deflection.  Try shrinking the size of the fixtured split faces in the solid model; the deflection might increase.

            • Re: Different displacement result, beam, surface and solid
              Mikael Martinsson

              Hi Chris.

              Thanks for your respons.

               

              My VAR solved this issue. The fault is mine and happened during the setup of the beam version..

              The "on flat surface" support on the beam version is not enough (beam element has 6 dof). I also need to prevent rotation in the axis between the joints to simulate the bending moment that occurs in the solid and surface solutions. When I add this restraint the solution gives similar results also in the beam version.