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Homework Help: Calculating Nominal strain at which Necking Occurs

  1. Jan 13, 2010 #1
    1. The problem statement, all variables and given/known data
    Given two wires of guage length 100mm and 200mm
    They are loaded to fracture in tension
    The 100mm sample extends by 15mm
    The 200mm sample extends by 25mm.

    I need to use this information to calculate the nominal strain at which necking commences in the wires

    2. Relevant equations
    These are the relavent equations i can find in my notes relating to necking, stress/strain, true stress/strain
    f42u0j.jpg

    we are also told, the true stress/strain curve generally represented by,
    fo1xmd.jpg

    where n is the work-hardening exponent

    "necking" in a sample started when the value of the true strain is equal to the work hardening exponent, i.e.,
    2cxvrwm.jpg


    3. The attempt at a solution
    Im not so sure where to start with this as there are no forces given or areas. I assume we have to use the two sets of data to equated these terms and cancel them out.
     
  2. jcsd
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