1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Principal stress at surface of thin walled pipe

  1. Nov 1, 2011 #1
    1. The problem statement, all variables and given/known data
    See attached jpg for problem statement and diagram.

    I know we didn't discuss this type of problem in class. The rest of this homework set has been solving stress transformations with Mohr's circles for a given state of stress. I know how to find τxy (that was supposed to be "tau"). So, once I find σx and σy, I know what to do with Mohr's circle to find the principal stress.

    If someone could point me in the right direction for how to find σx and σy, that would be great.

    Thank you!
    Any hints would be greatly appreciated.

    P.S.
    This is due in about 12 hours.


    ***Just remembered that my professor told us to ignore the internal pressure. So, to find sigma x and sigma y, I only use the 200 lb axial force?
     

    Attached Files:

    Last edited: Nov 1, 2011
  2. jcsd
  3. Nov 1, 2011 #2

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Have you set up an axis system and drawn a free-body diagram of the problem yet?
    Do you know how to determine the axial stress?
    Do you know how to determine the stress in the pipe wall due to internal pressure?
     
  4. Nov 1, 2011 #3
    1. Yes, I have.
    2. I believe so:
    A = ∏(0.5)2-∏(0.5-0.025)^2 = 0.0766 in2
    σax=P/A = 200 lb/ (0.0766 in2)
    = 2611.77 psi
    3. just remembered that we were told to ignore the internal pressure

    Is my axial stress correct? And how do I get σ1,2 from here?
     
  5. Nov 2, 2011 #4

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Your calculation of A is incorrect. Re-read the description of the pipe carefully.
     
  6. Nov 2, 2011 #5
    Oops. I read it as the outer diameter. Now I get A = 0.0805 in^2 and σ = 2484.37 psi.
     
  7. Nov 2, 2011 #6

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Sorry, A is still incorrect. You should review how to calculate the area of a circle.
     
  8. Nov 2, 2011 #7
    Wow. Maybe I should try doing homework when I am actually awake. diameter...radius
    So, A = 0.0131 in^2, and σ= 15238.1 psi.
     
  9. Nov 2, 2011 #8

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Sorry, you are just not calculating the correct A. you have forgotten to multiply by pi.
     
  10. Nov 2, 2011 #9
    Well, I think I've got it now, and in any event, I've now turned in the assignment.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Principal stress at surface of thin walled pipe
Loading...