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State of stress, strain and hookes law

  1. Nov 15, 2009 #1
    in the following question i am asked to find the state of stress given the state of strain.
    http://lh6.ggpht.com/_H4Iz7SmBrbk/SwBtHnG3qkI/AAAAAAAAB9M/rFS_orHMbGo/Capture.JPG [Broken]
    i went about solving this using hookes law

    [tex]\sigma[/tex]xx=E[(1-v)[tex]\epsilon[/tex]xx + v([tex]\epsilon[/tex]yy+[tex]\epsilon[/tex]zz)]/[(1+v)1-2v)]

    using the given
    E=30*106
    v=0.3
    [tex]\epsilon[/tex]x=0.001
    [tex]\epsilon[/tex]xy=-1.25*10-3
    [tex]\epsilon[/tex]y=-0.005

    i get
    [tex]\sigma[/tex]xx=-4.6154*104
    [tex]\sigma[/tex]yy=-1.8462*105
    [tex]\sigma[/tex]zz=-6.9231*104

    but as you can see these are not the correct answers according to the question.
    can anyone see where i have gone wrong ?

    also how do i find [tex]\tau[/tex]xy?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 16, 2009 #2
    [tex]\tau[/tex]xy=G*[tex]\gamma[/tex]xy=-0.0025*(30*106/2(1.3)=-0.0025*11.53846*106=-2.8846*104

    from this i already see that the answers are not going to be the same as the answers in the book, and there is nowhere i have gone wrong with the math here,

    am i doing something fundamentally wrong or could they be wrong with their answers,??
     
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