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Homework Help: Tricksy thermal stress question

  1. May 12, 2008 #1
    1. The problem statement, all variables and given/known data

    A steel rod 0.350 {\rm m} long and an aluminum rod 0.250 {\rm m} long, both with the same diameter, are placed end to end between rigid supports with no initial stress in the rods. The temperature of the rods is now raised by 60.0 {\rm ^\circ C}.

    What is the stress in each rod?

    Youngs moduli:[tex] Steel=20*10^{10},
    Aluminium= 7*10^{10}[/tex]

    Coef. of linear expansion: [tex]Steel=1.2*10^{-5},

    2. Relevant equations

    [tex] \frac{F}{A}= Y(\frac{\Delta L}{L_{0}}-\alpha \Delta T)[/tex]

    3. The attempt at a solution

    I am completely flumuxed, I know that that the total length of the two rods doesn't change but how do I find out which rod will expand and which be compressed? Any help getting started would be great.
  2. jcsd
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