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Homework Help: Calculate the stress/strain?

  1. Sep 4, 2015 #1
    1. The problem statement, all variables and given/known data
    The maximum proposed stress of their new design is 670MPa. You have measured the tensile strength of pieces of their steel, using an appropriate "standard" to guide you. (What does this even mean?) The load vs displacement graph is given. The steel sheet is 3mm thick. The width of the sample is 12.5mm and the gauge length sample is 50mm. Plot the stress strain graph.

    2. Relevant equations
    mm load, N
    7.52E-03 1.32E+03
    1.69E-02 3.30E+03
    2.61E-02 4.85E+03
    3.68E-02 6.53E+03
    5.02E-02 8.48E+03
    6.34E-02 1.05E+04
    7.74E-02 1.25E+04
    9.42E-02 1.44E+04
    1.04E-01 1.63E+04
    1.13E-01 1.81E+04
    1.27E-01 1.98E+04
    1.44E-01 2.14E+04
    1.80E-01 2.27E+04
    4.48E-01 2.34E+04
    8.10E-01 2.40E+04
    1.13E+00 2.47E+04
    1.47E+00 2.52E+04
    1.80E+00 2.57E+04
    2.16E+00 2.62E+04
    2.50E+00 2.65E+04
    2.81E+00 2.69E+04
    3.09E+00 2.75E+04
    3.42E+00 2.80E+04
    3.76E+00 2.83E+04
    4.18E+00 2.80E+04
    4.63E+00 2.74E+04
    5.12E+00 2.72E+04
    5.47E+00 2.67E+04
    5.71E+00 2.59E+04
    5.71E+00 2.49E+04
    5.71E+00 2.37E+04
    5.70E+00 2.21E+04
    5.30E+00 2.03E+04

    3. The attempt at a solution

    How do I find the stress for each load? I know that it is F/A, but I thought this only applied to rods and not a metal sheet? Or am i allowed to use 12.5x5 as the cross sectional area?
    Last edited: Sep 4, 2015
  2. jcsd
  3. Sep 4, 2015 #2
    Yes, you are, although it should be 12.5x3. What made you think that it only applies to a rod?

    It certainly applies to a sheet if the thickness and width are small compared to the gauge length.

  4. Sep 4, 2015 #3
    Thank you for clearing up the confusion!
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