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    Discussion in 'Calculations' started by chasan, Feb 26, 2010.

    1. chasan

      chasan Guest

      Someone please can help me to solve the following problem. which i need to submit Monday........ Thanks In advance.


      A thin walled pressure vessel is to be used as a pressure accumulator in a number of situations all involving a number of different operating conditions some of which create cyclic stresses. The dimensions of the vessel are 600mm long (not including end caps) and a shell outside diameter of 60mm. The material which the vessel is made from is pressure vessel steel with a yield 510MPa. a Failure stress 630MPa and an Endurance stress of 400MPa. Static stressing has shown that the vessel is safe for all the stress situations proposed and it must now be determined if the vessel is safe fatigue failure for the two following situations.

      1. If the vessel is subject to cyclic pressure of 0 and 400 bar determine the minimum shell thickness of vessel to give infinite life.

      2. If the vessel is subject to a cyclic pressure of 50 to 600 bar determine the minimum shell thickness of the vessel to give infinite life.
       
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    3. bkemper

      bkemper Member

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      I just joined so I missed your deadline. However:

      1. I don't know the specifics of your geometry, particularly your head. I also don't know which code (ASME, EN, API, etc.) you are designing to. Without this, there is no direct way to help.

      2. As a rule of thumb, stress = pressure * radius/2 (shell), or pressure * radius/2t (spherical head). From there, use 2/3 of yield as your design stress.

      3. For cycles...wow. All sorts of issues in play, including temperature, heat treat, how the vessel is anchored. As a very very very general rule of thumb, if your beak stress is less than 20% of MAWP, you don't have to worry about fatigue (ie, "infinite life.") Granted, this beefs up your design. You also have to consider long term loads (temperature, pressure, etc.) as well as short term (upset, earthquakes, etc.)

      Hope this helps.
       
    4. chasan

      chasan Guest

      I am a student in university. i am doing this for the module materials failure for fatigue design. so i don't have to consider about the temperature and everything. i just want to do the fatigue calculations. i hope it is just a simple thing for you. i look forward for your reply.
       
    5. kvengel

      kvengel Member

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    6. kvengel

      kvengel Member

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    7. mvalenti

      mvalenti Well-Known Member

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      Re: Determine the minimum shell thickness of pressure vessel

      psst.... what about hoop stress?
       

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