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Thermal Expansion Stress

  1. Jan 24, 2010 #1
    I'm designing a system that will thermally cycle a stainless steel substrate up to 1200C from room temperature; right now my design consists of clamping the substrate onto a plate using a bolt head/washer with a nut on the other end of the screw, as shown on the attached figure.

    I want to determine the minimum distance I can put the substrate away from the bolt so that buckling will not occur during thermal expansion. The substrate in question is 4"x1"x1/16" (the 1" is into the figure). The bolts I have selected have a 3mm nominal diameter and are made of Monel.

    I calculated the critical compressive stress on the substrate to be 22.9 ksi, but I am having trouble incorporating the thermal expansion of both the sample and the bolt in order to determine the compressive stress on the sample. What steps should I take?

    Here's some material info I got from matweb.com:

    [tex]\alpha_{stainless steel}[/tex]=15.1E-06 /degC, E[tex]_{stainless steel}[/tex]=28.5E+06 psi, S[tex]_{y, stainless steel}[/tex]=89.6E+03 psi

    [tex]\alpha_{bolt}[/tex]=13.9E-06 /degC, E[tex]_{bolt}[/tex]=24.5E+06 psi
     

    Attached Files:

    Last edited: Jan 24, 2010
  2. jcsd
  3. Jan 25, 2010 #2

    minger

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    Science Advisor

    When looking at thermal stresses, the typical approach is superposition. Assume that you have a beam fixed between two supports and heat it. You can think of there being two loads: one thermal, and one mechanically imposed by the support.

    Typically one would allow a free end to move as if it were not being constrained. You would then calculate the load required to move it back into place.

    I hope that gets you on the right track. If you need an example I'm sure someone can provide one.
     
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