1. Limited time only! Sign up for a free 30min personal 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!

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

    User Avatar
    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.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook