6 Replies Latest reply on Nov 15, 2017 10:22 AM by Andrew Cuttle

    Closing a gap

    Daniel Schulz

      Is there a way to force a contact set closed, analogous to a shrink fit, but with a gap instead of interference?  A shrink fit contact set gives me an error that interference is required.

       

      I'm trying to close this gap...

        • Re: Closing a gap
          Daniel Schulz

          I think I've got it.  I applied a proof load to each connector to close the gap, and defined the contact sets as 'no penetration'.

           

          No - that won't do it.  I'm compressing the bearing housing doing that.  I'm trying to figure out how this assembly will affect my bearing press fits.  The housing is aluminum, the rest is steel.

           

          Maybe a force couple for each fastener.  Seems like shrink fit should work, and would make life a lot easier.

            • Re: Closing a gap
              Greg Hoepfner

              Not knowing what your loading case is, you could perhaps close the gap through a prescribed displacement of the face equal to the gap distance and use a no penetration contact.

                • Re: Closing a gap
                  Daniel Schulz

                  The whole assembly stretches, so it's unknown how much each part stretches.  The only loads  I'm considering are the fastener loads, which will close the gap.  I'd like to see how much these assembly forces affect the bearing press fit.  In effect, that prescribed displacement is exactly what I'm trying to determine.

                    • Re: Closing a gap
                      Andrew Cuttle

                      I think a variation Greg's suggestion is probably the simplest: a conservative assessment would be to only consider the arm and apply a displacement sufficient to close the gap up, and read the reaction from the constrained end. The other components would have some flex in them but proportionally it will likely be much lower than that of the arm.

                       

                      If you wanted a secondary check after that stage, you could could apply the reaction loads from the arm to the hub and outer wheel individually. This will give you conservative stresses for those items. If you saw significant displacement in those members then you would know that the analysis is overly conservative and you might need to refine things.

                       

                      For both the wheel and hub assembly, running things as a quarter model would probably make the constraints simplest.

                       

                      If you were set on analysing the assembly as a whole, with a quarter mode, you might be able to use the bolting force as a beam element with pre-load applied, but I'm not sure if you can do that in SW. I've only done so in more complete packages.