6 Replies Latest reply on Apr 4, 2012 3:54 PM by Chris Breen

    Face to face shell issue...Help

    Chris Breen

      Hello,

      When working with shell elements does it matter which face of the mid-plane you select to contact another shell? I am analyzing a brazement and the best way to represent the model is to utilize shell elements due to the thin features. This issue that I am running into is where a contact set that mates two shell faces together and randomly neglects to account for itself while the analysis runs.  I had one lucky time where the constraint accentually functioned as it should but then regressed in the next run.  I understand that you can look at the shell “top and bottom” in the colors generated in the mesh; however, nothing seems to be working.  I have deleted and re-contacted multiple times.     I am in 2011 by the way

      Please help!

      Chris

        • Re: Face to face shell issue...Help
          Rohit Mitra

          A screenshot of what you're trying to do would be helpful

            • Re: Face to face shell issue...Help
              Chris Breen

              Unfortunately I cannot supply a screen shot as the analysis is on a computer that is locked down.  Picture two parallel plates, there is nothing complicated about the geometry in the model.  My main question is if it matters what side of the shell you select to contact another shell when they are both represented by midplanes.  I have search far and wide for an answer to this but I am coming up empty and it is starting to wear on me as this analysis has become drawn out when it should not have been.

                • Re: Face to face shell issue...Help
                  Rohit Mitra

                  You want to select the same side of each plate, so that the orange side of the meshes and gray sides match up. If they are not matched up, you can click on one of the faces, then right click on mesh in the simulation manager and choose flip shell elements. The study should work fine if these are lined up; it will fail if the wrong faces are selected however.

                    • Re: Face to face shell issue...Help
                      Bill McEachern

                      the side doesn't matter. How far apart they might though. I thought they fixed this but maybe not. I would not have the separation disance much beyond the thickness of either plate involved. In previous relaeases distances beyond 1 or 2 t would  not bond.

                        • Re: Face to face shell issue...Help
                          Toby Schnaars

                          I agree with Bill.  Surfaces don't have "inside" or "outside" or "top side" or "bottom side".  Just one surface, so it doesn't matter whether you pick it on positive Z or negative Z.  In face, if you select a surface so that it highlights in blue, and then rotate your model, you will see that it is highlighted on "both sides" (since it's one single surface).

                          • Re: Face to face shell issue...Help
                            Chris Breen

                            Bill,

                             

                            Thank you for adding some validation to whether or not the side of a shell is important in a bonded constraint.  I was reading elsewhere that the selection of “more accurate” under incompatible mesh options in the study’s properties can cause trigger a neglect in bonded mates, have you heard of this?  I am running another variation to see if this actually has an effect on bonds. 

                             

                            The 1 to 2t rule is one that I will note for the all future shell building.  The current assembly of shells is a .05” thick plate and a .002” thick shell; this obviously goes against the 1 to 2t rule of thumb as they are both represented at their respected mid-plane.  Do you have any suggestions on how to proceed with this without modeling the .002” component as a solid?  Any advice will be warmly accepted as I would like to choke out my computer at this moment.