11 Replies Latest reply on Apr 8, 2015 7:55 AM by Sindre Sorhus Branched to a new discussion.

    Circular symmetry on 1/3 "slice"

    Thomas Juul

      Hi!

       

      I am trying to do circular symmetry one a part that is split in 1/3, but SolidWorks misinterpret what I am trying to do. It multiplies the part 6 times around the symmetry axis instead of 3 times as it is supposed to be (see attached screenshot).

      11096918_10206455950865459_1846584246_o.jpg

       

      I cannot get it to work, and normal symmetry won't work since the two connecting faces are not perpendicular and I have tangential forces. Is it just not possible?

        • Re: Circular symmetry on 1/3 "slice"
          Jared Conway

          do you really need circular symmetry? ie are your loads patterned tangentially?

           

          if not, just use symmetry manually by applying a normal restraint on those cut faces

           

          there were a couple discussions about this recently that you might want to check out

            • Re: Circular symmetry on 1/3 "slice"
              Thomas Juul

              For the loads I have used the centrifugal function with angular acceleration. So yes I guess the loads are patterned tangentially, but if I just restrain the cut faces then the "disc" won't be able to deform around the rotational axis (which it should due to the angular acceleration)? 

               

              I have been looking through some of old threads, but I don't think I stumbled upon something that solves my problem?

                • Re: Circular symmetry on 1/3 "slice"
                  Jared Conway

                  i'm surprised this one isn't popping up: Re: Why Can't I Select Axis for Circular Symmetry?  it is shown in the right hand side of this thread on my system.

                   

                  i haven't specifically used symmetry with regular centrifugal loading or cyclic symmetry with centrifugal loading with angular acceleration but they seem like they would be compatible.

                   

                  i'm not sure i'm following your comment about the restraint. all the methods you describe are also restraints. but if you're concerned with the methodology, run the full model and also the symmetry model. maybe something to note is these are body loads, the parts won't actually spin.

                   

                  going back to your original problem, what version/sp are you using and can you post the model?

                    • Re: Circular symmetry on 1/3 "slice"
                      Thomas Juul

                      I have been through that post, but it doesn't seem like there is anything that helps me other than a slim definition of symmetry and circular symmetry. Are there by the way a fulfilling description of what SW does when applying symmetry (more than is described in SW Help)?

                       

                      What I meant regarding the restraints is that if I fix both cutfaces, then the disc won't be able to deflect as seen here:

                      not deformed.PNG deformed.PNG

                      The model is a extremely simplified version to experiment with these issues. You should be able to download it here: https://www.dropbox.com/s/abisw8l1sk1y2o9/Spinning_object.zip?dl=0

                      The model is build in SW 2015 Student Edition.  

                        • Re: Circular symmetry on 1/3 "slice"
                          Thomas Juul

                          As a new user to this forum I accidentally moved Jarey Conway's repost to another thread, but here it is:

                           

                          Jarey Conway wrote:
                          "

                          "I have been through that post, but it doesn't seem like there is anything that helps me other than a slim definition of symmetry and circular symmetry. "

                          >> this is the reason I recommended taking a look at it. to ensure that you know which BC that you should use.

                           

                          "Are there by the way a fulfilling description of what SW does when applying symmetry (more than is described in SW Help)?"

                          >>as an educational user you are somewhat limited, you can speak to your instructor they may have access to the solidworks KB that has additional information. but also, this BC uses the standard definitions of symmetry for FEA.

                           

                          "What I meant regarding the restraints is that if I fix both cutfaces, then the disc won't be able to deflect as seen here:"

                          >>this is why i recommended that this is unlikely a good BC for your case. remember that symmetry requires that in addition to the geometry and loading conditions to be symmetric, the results/behavior also need to be symmetric."

                            • Re: Circular symmetry on 1/3 "slice"
                              Thomas Juul

                              "What I meant regarding the restraints is that if I fix both cutfaces, then the disc won't be able to deflect as seen here:"

                              >>this is why i recommended that this is unlikely a good BC for your case. remember that symmetry requires that in addition to the geometry and loading conditions to be symmetric, the results/behavior also need to be symmetric.

                               

                              ** Both the geometry and loading is circular symmetric, and if I do a simple study on for example a 1/6 slice the circular symmetric constrain seems to work just fine. Through my experience here it seems like everything else than a 1/3 slice works.

                    • Re: Circular symmetry on 1/3 "slice"
                      James Riddell

                      Did you try your circular symmetry by slicing down the center of the 'prong' sticking out of the edge of the disc?  That should cure the SW mis-interpretation of the geometry I would guess.  I have no idea why it would 'think' that there was something there but that's just me expecting software to behave logically.

                       

                      If you have a VAR this looks like a good candidate for a 'software improvement'.

                      • Re: Circular symmetry on 1/3 "slice"
                        Sindre Sorhus

                        Hi Thomas,

                         

                        This is only a problem if you have a cyclic cut that divide the part into 120deg section. If you have smaller angles that can be divided by 360, you will not see that issue. The problem is covered by the following SR and a solution is implemented into 2015SP3

                         

                        SR 854268 - SOLIDWORKS Simulation - Postprocessing: Display symmetric results option works wrong for the model with Circular symmetry for 120 degree.