3 Replies Latest reply on Jun 27, 2016 1:49 PM by James Riddell

    Tie Down Restraint Fixture

    Nick Morris

      I am trying to set up a simulation representing a large payload being strapped to the deck of an aircraft. The payload has tie downs with cylindrical holes along both sides which allows a shackle to be attached and then tied to the ground. How would I represent that within simulation as far as Fixtures are concerned without over restraining the model? I considered doing a split line to represent where the shackle will sit when tension is applied, but not sure about the directions to restrain it in.

        • Re: Tie Down Restraint Fixture
          James Riddell

          I'd suggest you put in a plane perpendicular to the direction of the restraint and limit in that direction only.

            • Re: Tie Down Restraint Fixture
              Nick Morris

              So here is a little better view of the tie down point. I put a split line in and applied an advance cylindrical face fixture on that split line and have is restrained in the X-direction. This would allow movement in all other directions right? If say I apply a G load in the Y direction... Its a very large assembly and takes a while to run so only want to apply the bare minimum. But obviously not over restrain it and get inaccurate results.

               

              Not exactly sure how the plane perpendicular to the the tie down would work. Still rather a novice at Simulation.

                • Re: Tie Down Restraint Fixture
                  James Riddell

                  Because I can't see the complete assembly (I'm sure it is confidential to some level) I'm not sure if your restraint is the way you show.  If you could add a red arrow pointing in the direction of the cable/chain/strap that is in tension I would be able to give you a better answer.

                   

                  However, having said the above, I can't imagine a case where part of a cylindrical surface would 'hold' along the axis of a hole (unless it is sliding friction only).  Imagine a clevis with a bolt through a hole - the bearing surface is in a direction in line with the way the clevis is being pulled. 

                   

                  Further, just holding a surface/edge/point in one direction does not mean that there is not an X-Y-Z force generated by something like the roller/slider (1D) constraint.  Verify and validate.