6 Replies Latest reply on Mar 21, 2011 8:26 AM by Garrett Casey

    Backing out force from a press fit simulation

    Garrett Casey

      So the idea of this simulation is to press fit the Teflon piece into a hole in the aluminum plate.  Now I may have the simulation set up incorrectly, but I've defined a global 'No Penetration' Contact Set, set my aluminum plate as fixed geometry, set a roller/slider as the cylindrical face so that it can move along that axis, and applied an advanced fixture moving the Teflon piece downwards 5mm.  I would like to back out the force required on the face of the Teflon piece to press fit this piece into the hole.  Any suggestions to solving this problem would be great or if I'm going about it the wrong way, please let me know.

       

       

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        • Re: Backing out force from a press fit simulation
          Anthony Botting

          Use the "Shrink Fit" contact set, post assembly. It was designed specifically for that purpose. Click the question mark (?) on the PM to open the Help for the instructions on setting it up.

          • Re: Backing out force from a press fit simulation
            Peter Biggert

            The force equals (Contact Pressure)x(Contact Area)x(friction coefficient)

             

            The size of you hole and thickness of the plate gives you the contact area.

            Use Anthony's suggestion to calculate the contact pressure.

            I hope you have a good value for the friction coefficient between aluminum and teflon.

            • Re: Backing out force from a press fit simulation
              Wayne Matus

              The shrink fit analysis will give you the contact pressure, but not the force required to press the pin in the hole. You could use the contact pressure given in your FEA analysis in hand calculations to solve the force required. I have used "Marks' Standard Handbook for Mechanical Engineers" for pressing steel shaft on steel hub. Not sure what the formula would be for your dissimilar materials.

               

              If you want to do it all in FEA, you would need to do a nonlinear anayysis on assembly with the pin outside the hole. Apply surface to surface contact elements between the hole cylindrical face and the cylindrical face of the pin. The coefficient of friction on the contact elements will effect the results. Then apply a specified displacement on the end of the pin over a period of time. You can then extract the reaction forces on the end of the pin to get the press fit forces.

              • Re: Backing out force from a press fit simulation
                Garrett Casey

                What I ended up doing for this simulation was to add the shrink fit contact set situation and apply a fixed geometry condition at the top of the piece being pressed in.  This allows it to expand downard slightly but also give a force pressing upward.  It seems to me through experimental data that this force is roughly equivalent to the value we are seeing experimentally.  The force we are looking for isn't critical that we are accurate to tenths or hundredths of pounds-force but rather than we have a ballpark figure.  Does the method of simulation make proper sense?