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Mohr circle for 3dimensional stress state

  1. Apr 14, 2005 #1
    I am not sure how to draw a mohr cirlcle on a 3d stress state. I haven't seen
    any website sofar. Is it being used by engineers these days or some alternate
    method is available.
  2. jcsd
  3. Apr 14, 2005 #2


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    I doubt that many engineers actually use the Mohr Circle analysis anymore. There are so many neat Finite Element modeling packages out there that the art of doing stress analysis by hand is virtually extinct.
  4. Apr 14, 2005 #3


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    I use it occasionally, just to keep my head into the theory and if the problem is simple enough.

    A 2 second search yielded the following
    http://me.queensu.ca/courses/MECH422/Lecture5a.ppt [Broken]
    http://portal.cs.umass.edu/projects/mohr/ [Broken]
    http://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2003.pdf [Broken]

    There's plenty of information out there on how to do this technique.
    Last edited by a moderator: May 2, 2017
  5. Apr 16, 2005 #4

    unfortunately the links doesn't tell me how to draw the three circles from
    the scratch. Can you pls.
  6. Apr 16, 2005 #5


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    Are you familiar or have studied the two dimensional Mohr's circle?
  7. Apr 17, 2005 #6
    I have studied plane stress state(i.e 2d) and know how to draw a 2d mohr
  8. Apr 23, 2005 #7


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    Here's a quickie:

    http://www.aoe.vt.edu/~jing/java/nsfapplets/MohrCircles2-3D/Theory/theory.htm [Broken]

    This is from the same site that has an appelet to draw them for you:
    http://www.aoe.vt.edu/~jing/java/nsfapplets/MohrCircles2-3D/Applets/applet.htm [Broken]
    Last edited by a moderator: May 2, 2017
  9. Apr 24, 2005 #8
    in this link there is reference to the eigen value. example they say "the
    two principle stresses are the eigne value of the 2x2 matrix of sigmax and tauxy"

    I was looking for a practical application of eigen value. can you now tell this
    what is an eigen value?
  10. Apr 24, 2005 #9
    I am not getting it. How to draw the 3 circles(centre and diameter of the circles).
  11. Apr 29, 2005 #10
    eigen value can help with the mohr circle but it's really really long from what i jus reviewed... anyhow i have a book that explains ti and i dont' have a digital camera but this book is pretty good...

    Mechanics of Material by Ferdinand P Beer

    from the book it gives
    sigY = 3.5
    Sigx = 6
    txy = - 3ksi

    The book i'm lookin at develops the mohr circle by tne normal sigAVE(4.75ksi) equation
    from that you know the center of circle and the radius (3.25ksi) etc

    Now the bigger circle comes from the principla streseses
    which is 8ksi and 1.5ksi.
    now from 0 to 8 is the new diameter of the third circle
    and from 0 to 1.5 is the small circle
    and from 1.5 to 8 is the medium circle...

    das what the book has and i guess the key is your principle stress....
  12. Mar 13, 2010 #11
    Hi Guys,

    Can someone advise me how you would find the sigma(x), sigma(y), tau(xy) values?


    also...is the following equation valid for 3d models...

    Smax= 0.5*(Sx-Sy) + 0.5*(sqrt( ((Sx-Sy)^2) + (4*Tauxy^2) )
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