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Desining a aluminium rod

  1. Aug 12, 2012 #1
    Hi guys,
    I'm studying my first semester in engineering, I was giving the first assignment in my material science class which I'm not so sure on how to get started on.

    The assignment was to ask us to design a aluminum rod which has the following specification:
    1) Withstand an applied force of 200kN
    2) Maximum allowable stress on the rod is limited to 170Mpa with a strain of 0.0025mm.mm^-1
    3) Rod must be at least 3.8m long but deform elastically no more than 6mm when force is applied

    I was thinking of a "I" shape rod, but am not sure were I on the right track or what should I include (e.g. width, depth, and shape) to sufficiently uphold the conditions.

    Secondly can someone please tell me how do I convert load-guage length to engineering stress and strain?

  2. jcsd
  3. Aug 12, 2012 #2
    How is the force to be applied, along the length of the rod, or at 90 degrees?
  4. Aug 12, 2012 #3
    the question is just say "An aluminium rod is to withstand an applied force of 200 kN".
    I guess its at orthogonal
  5. Aug 15, 2012 #4
    If the load is applied perpendicular to the rod (orthogonal), then you need to know the boundary conditions on the ends, and solve the problem as a beam bending problem. It sounds like, in this problem statement, a tensile load is applied on the ends. Try out some different shapes and see what you get. Start with a circular cross section for simplicity. Why? If you can't solve that, you are not going to be able to do more complicated cross sections.
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