Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stress Analysis - Annulus Circular Plate

  1. Apr 10, 2012 #1
    I'm doing stress analysis on a circular region on this part where an o-ring seals against.

    There is a 7500 PSI normal force being applied on it.

    So you can think about it as an annular circular flat plate (like a washer) with the 7500 PSI force uniformally distributed on the surface.

    I want to analyze things like the max bending moment & stress if it is fixed on the inside edge...

    and shearing stress.

    Help would be appreciated..

    Also as a side note:

    How would you convert that pressure (7,500 PSI) to a force per unit length versus per unit area?

  2. jcsd
  3. Apr 10, 2012 #2

    As for it being for a force per unit length, this didn't make much sense to me. The closest thing I found quickly online was surface tension (Newtons/meter). See here: http://en.wikipedia.org/wiki/Surface_tension

    But if you want to know the force... PSI stands for pound-force per square inch

    You could just use 7500 pounds force as the force (per square inch). So if the area of your washer is 5 in2, your force would be 7500lbf/in2 * 5in2 =37500 lbf.

    So if you find your washer is suitable to support a pressure of 7500PSI, you could say that it is suitable to a force that is equal to the PSI * the area.

    Of course, if there is any way somebody could get hurt, which I assume there is with this much pressure, you need a more detailed analysis of the physical structure and it's assembly.
  4. Apr 13, 2012 #3
    Not entirely sure, but for a rough estimate you could take a strip of the circular plate, then analyse it as a simple cantilever. Get your moments, shear forces, stresses and integrate it over the inner circle. That should atleast provide a sanity check to a FEM model.
  5. Apr 13, 2012 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hi Harrisiqbal,
    Do you have a copy of Roark's Formulas for Stress and Strain? This is one of the 'bibles' of stress analysis and is especially useful for things like this. Every mechanical engineer working on stress analysis should have a copy.

    This particular case is shown in Table 11.2, case 2l on page 467. Outer edge free, inner edge fixed, pressure load on circular (annular) face. The equations there provide all the information you need to calculate transverse and radial stress and deflection at every point.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook