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Thread: What is the equation for....

  1. #1

    What is the equation for....

    I'm back with another crazy, shop built project.

    Think of a HF hydraulic press.

    The columns have to resist a tension load.
    I'm building something similar, a device to proof test electric hoists.

    How do I figure out how much stress a particular tube, say 4"x4"x .250 wall, will stand before deformation?
    I can't find anything like that in the list of formulas...

  2. #2
    Administrator Kelly Bramble's Avatar
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    The equation is just the tension force divided by the pipe section area or force/area^2


    The results will be on lbs/in^2 or N/mm^2.


    or, you can use this calculator setting Fy=0 and fx = applied tension loading.


    https://www.engineersedge.com/beam_b...d-stress-2.htm


    or this one setting the torque = 0


    https://www.engineersedge.com/beam_b...-stress-10.htm
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  3. #3
    Thanks for that.
    I used both equations, and got the same answer. (That's good!)
    But I seem to be having a bit of a 'senior moment'... indulge me if you will.
    The Maximum Tensile Stress is xxx psi.
    The area in the example tube above is 4 square inches.

    How do I take that info and use it to determine if the example tube above will be able to resist that force without deforming?
    (I have to say, this seems like it should be a very simple problem, but... )

  4. #4
    Administrator Kelly Bramble's Avatar
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    Compare the calculated stress (lbs/in^2) to the yield strength of the material.

    If the material is 1025 carbon steel the typical yield (permanent deformation) is not less than 40,000 lbs/in^2 (psi).

    See

    https://www.engineersedge.com/manufa...s_strength.htm

    So, if you calculate a maximum applied stress of 15,000 psi and the minimum rated yield is 40,000 psi 40,000 psi / 15,000 psi give you factor of safety = 2.6

    I recommend a FOS not less than 2 on verified material yield.

    To convert Pa (Pascals) to lbs/in^2 (psi)

    Pa x 0.000145038 = psi

    to convert psi to Pa

    psi X 6894.76 = Pa
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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