General Mechanical

General Mechanical

Air pressure that seal will support

    • Chinmay
      Subscriber

      Hi all, greetings.

      Here is the initial and final position of my simulation.

      Initial:

    • Erik Kostson
      Ansys Employee
      Hello

      Suppose one way is to apply your air pressure on the component and ramp it up to see when you lose contact completely so your contact is not on and hence your contact pressure is 0 (means the seal is not touching the face anymore).

      All the best

      Erik
    • peteroznewman
      Subscriber
      @chimay
      Note that you will have to split the face on the seal at the line where the contact is closed. The contact pressure in psi is plotted below, the transition from grey to color is at 20 psi and the peak pressure is 88 psi, so we can expect that the seal will fail somewhere between 20 and 80 psi.
      You would need to split the face at the contour line between grey and blue. That way, you would put a test pressure of say 50 psi on the faces that are above that contour line, and there would be no pressure on faces below that contour line. Solve the model and check how much the 50 psi contour line moved relative to the split line.
    • Chinmay
      Subscriber
      Thank you for your reply but I am quite new (only few months of experience in Ansys Structural) to Ansys WB. Thus I am really not sure how to perform those activities you guys mentioned. I will look up other resources available and try few ideas on my own.
      Btw if the maximum value is 88 Psi or 0.6 MPa for contact pressure, does it mean it will need equal and opposite force to break the contact ? So basically we need to apply pressure on face of seal to bring that value to zero ?
      Thank you Chinmay
    • peteroznewman
      Subscriber
      While the maximum pressure on the seal is 88 psi, that is only in the corner. On the side, the pressure drops to about 70 psi (light orange color). The seal fails when the lowest value around the perimeter fails. There is a natural split line on the geometry, so simply choose all the faces above that to apply a pressure.
      Under analysis settings, make this a 2 step solution. In step 1, the pressure is 0 and the displacement of the center part ramps up to 5 mm in 1 second. In Step 2, the displacement stays at 5 mm and the pressure ramps up from 0 to 100 psi in 1 second.
      I followed my own instructions and was interested to learn that the pressure actually helps the seal work better! Below is the pressure at 76 psi (time = 1.76) and you can see the peak contact pressure is now 170 psi because the pressure is pushing down on the top of the seal, which causes it to compress against the bottom and expand sideways making the contact pressure increase.

    • Chinmay
      Subscriber
      You are absolutely right and the solution is correct based on given inputs. My bad I didn't mention the exact parameters of the seal and the pressure direction.
      The air flows from the direction shown and applied a 2 bar or 0.2 MPa or 29 psi pressure on highlighted faces, probably pushing seal in right direction (if it is sufficient to overcome friction between seal and other bodies).
      But as you correctly mentioned above, this pressure is going to increase the contact pressure between seal and other bodies at the seal lip, so doesn't this mean that there is less chance of failure (air escaping through seal) now ?
      Thanks Chinmay

    • peteroznewman
      Subscriber
      Yes, pressure improves the seal, if there is an initial seal.
      One type of failure is if there is a gap after assembly. The air will flow through the gap and the pressure will open the gap.
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