4 Replies Latest reply on Jun 9, 2017 5:37 PM by Paulo Onarres

    Rubber gasket "tight fit" simulation

    Paulo Onarres

      Hello all,

       

      I am trying to find out how much force I need to apply to a part in order to deform a rubber gasket enough to get it to pass through a constricted area. I have set up a non-linear dynamic simulation with the gasket and the outer and inner metal profiles. To make processing time faster, I only have a 1 degree revolve of each of the parts. The lowest part is fixed completely. The upper metal part has a cylindrical fixture (no movement) and a fixed downward displacement of 30 mm.

      I want to squeeze that gasket and see how much force it takes on the upper metal part to get it through. It should be easy enough but I get an error every time.

       

      Does anyone have any ideas? I've included the files in this post. Thanks!

       

      Context: This gasket is what's called a "shear gasket". Notice that it has a hook shape. It is meant to pass through a tight spot (like the one modeled above) in order to hook onto the metal profile below. The purpose of this is to provide some resistance being pulled back up involuntarily but at the same time allow it to shear (and those allow part recovery) when pulled on with enough traction. Basically you push the part down and can only pull it back up once you have enough tension to shear the gasket.

        • Re: Rubber gasket "tight fit" simulation
          Keith Frankie

          This is a perfect candidate for 2D simplification.  This will take the computation from 'excessively complicated' to 'reasonably quick'

           

          You have this set as a dynamic study.  Is that really necessary?  A nonlinear static study (ignoring inertia) would probably be sufficient.

           

          I'd start by creating a rigid connection between the top of the gasket and the inner ring.  Since the gasket doesn't have a precise fit with the ring in that area you'll have trouble getting good contact.  This part of the gasket isn't really involved with the compression of the lip, so removing this flexibility shouldn't affect your accuracy.

          • Re: Rubber gasket "tight fit" simulation
            Bill McEachern

            The large displacement contact problem requires a non linear solution suing a fixed displacement loading condition. The results will depend on the friction coefficient specified. this can probably be solved an a 2D simplification is probably a good way to go.

            The other option is to put the assembly in the final position and use a shrink fit contact condition and just solve the shrink fit. You can get the contact normal force and you can multiply that by the friction coefficient to get an estimate of the required insertion force. Again if the problem is axisymmetric a 2D simplification would be a sensible way to go.