13 Replies Latest reply on Jan 23, 2016 5:51 PM by Brandon McCool

    Simulation Meshing Interference

    Brandon McCool

      I have been struggling with interference of my part file and am in search of help. I have tried many different things with contact points with and without penetration, bonded contacts, shrink fit, incompatible mesh etc. I cannot seem to find a breadth of information/guidance on this. I will say that while I have tried using these, I may not have tried everything or selected the right things to make them work for the simulation. The fixed geometry is the bottom plate. The force is 15 lbf on the tail "seat". The material doesn't much matter at this point, I just want to get this working.

       

      There are a few things I have tried that have bypassed the meshing errors, but then the simulation fails to complete. I have included the SW file and a picture of the error. The only difference between the file in the picture and the most updated one (which is attached, 6) is I tried changing some of the geometry where the interference for the first pair of bodies was.

        • Re: Simulation Meshing Interference
          Janko Stellaard

          Hi Brandon,

           

          This error message means that you didn't constrain the model properly. So some parts of the model are not properly fixed, or some contact definitions are missing. There is a part (or more parts) that have a very large displacement because they are not attached to the rest (or fixed).

           

          Janko Stellaard

          Cadmes BV

          The Netherlands

          • Re: Simulation Meshing Interference
            Janko Stellaard

            Your meshing problem is solved by:

             

            • In your global contact definition, change 'compatible' to 'incompatible'
            • Select 'standard mesh' with the minimum mesh size (slider to the right)

             

            Now it meshes without a problem

              • Re: Simulation Meshing Interference
                Brandon McCool

                It worked! Now that I can begin trial and error to reduce as much material as possible, SolidWorks is having trouble with fillets. To reduce the stress concentrations at the corners of the very first cutouts, I want to add fillets. It varies as to when the program stops working but I can get anywhere between 0 and 3 fillets completed and rebuilt before the screen goes opaque and stops responding. I'd imagine it struggles because the geometry of the body curves through all three dimensions. Windows checks for solutions but never turns anything up.

                 

                Any suggestions? I'd prefer not to have to return to the sketch that created the geometry and add in a sketch fillet.

              • Re: Simulation Meshing Interference
                Leszek Paprota

                Hi Brandon,

                 

                there are some geometry issues,

                add the part to a assembly and run the interference detection detection. there are a quite a lot of those.

                 

                Or

                you can merge this to one body with the combine feature. -it will not make a difference for your simulation, as you have a global bonded contact.

                 

                but if you want to get more information from your static analysis you will have to fix the interference.

                hope this helps.

                 

                Leszek

                  • Re: Simulation Meshing Interference
                    Brandon McCool

                    Thanks for that. I have seen people use the Interference Detection feature but did not realize I could use it with a single part within an assembly. I noticed you have that box checked.

                     

                    I just don't understand how this happens. I use coinciding geometry to create other bodies and surfaces to make cuts, etc. so just about everything references everything with offsets and up to surface extrusions/cuts. Many of the interferences are tiny, and some are barely visible when highlighted. I do know that SolidWorks cuts corners with the graphics to increase performance so it can be difficult to tell, but I don't see how using existing geometries can create interfering bodies.

                      • Re: Simulation Meshing Interference
                        James Riddell

                        Brandon, that is exactly my point below.  Any inaccuracy in geometry shows up in FEA - no shortcuts.  You may have references that cause these and it is usually best to break the dependencies. 

                         

                        Also check that you don't have small gaps/slivers - if surfaces don't touch then they can't share common nodes.

                         

                        Clean geometry is happy geometry.

                          • Re: Simulation Meshing Interference
                            Brandon McCool

                            So you are saying I cannot get by with using the "Incomplete mesh" during the simulation of a part file with multiple bodies? The simulation is missing contacts, as shown in the picture. The piece that joins the two siding sheets of plywood is illustrated. On the far side, it works as intended. On the closer side the simulation acts as if the joiner is not even there. I have tried to add contact sets but it doesn't seem to help. The siding also pulls away from the front former and the bottom landing gear plate. I'm sure this reduces the stress that is being computed and reported because the bodies are not maintaining contact.

                             

                            I have cleaned up a lot of the interferences, but these few are making me continue to second guess the FEA results.

                              • Re: Simulation Meshing Interference
                                James Riddell

                                It not so much the 'Incompatible Mesh' as the physical interference.  If you clean up the surfaces so they match perfectly and the two parts are bonded then they will share nodes and therefore transfer displacements as expected.  Gaps are a similar problem; if parts don't connect and the forces move them apart then they, obviously, won't transfer displacements the way you might expect.

                                 

                                Always 'second guess' your FEA results; they should make sense.

                                  • Re: Simulation Meshing Interference
                                    Brandon McCool

                                    How can I go about creating artificial bonded contacts? That contact area in the picture I posted earlier really has no excuse not to be fully bonded. Here it is again but I found the contact visualization tool and it's exactly what I've been looking for, in terms of seeing what needs fixing. I made the right and left side the same way, using 0" offset surface and then trimming the surface down by intersecting ruled surfaces based off a sketch I made that had the cut outs I wanted. It uses the exact geometry, yet fails to show contact area.Contact.png

                                    So how can I create artificial contacts? Whenever I try to add Component Contacts, they don't seem to do anything. I am messing around with the non-touching faces condition right now. It looks like it may have worked a little.

                                      • Re: Simulation Meshing Interference
                                        James Riddell

                                        Ah, now it seems you have stumbled on one of those pesky 'undocumented features' in SW.  I've seen the same thing where parts which are mated do not bond using Global Bonding for some unknown reason.  The only way I've found to work around this, short of making an entirely new model, is to use the Contact Sets feature to find and bond surfaces of selected parts with the rest of the assembly.  Select the part, choose the option to 'find with the assembly' and search automatically.  Then you need to select the ones you want to create from the window in the bottom.

                            • Re: Simulation Meshing Interference
                              James Riddell

                              Best practices: ALWAYS remove/fix interferences in an assembly before meshing.