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Thread: Does total reaction force exerted on bolt need to take account clamp force ?

  1. #1

    Does total reaction force exerted on bolt need to take account clamp force ?

    my bolt is tightened with certain torque and it produce tensile/clamp load due to it, FC . then the bolt is exerted experience external positive/negative tensile force,Ay on it.
    Does the total reaction force on that bolt is
    Ry=Ay +/- FC,
    or just
    Ry=Ay.



    for your reference (A left, B right)

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    Last edited by Kelly Bramble; 11-26-2015 at 02:31 PM.

  2. #2
    Associate Engineer
    Join Date
    Oct 2015
    Posts
    4
    Hi enotyphoon.

    I am not a graduated engineer yet, so tread my comments cautiously. But here's my opinion.

    Bolt A: I think you know already know that but I prefer to be sure, this happens if the external load separates your 2 layers of plates. If the external load applies in the same direction for both plates there will be no additionnal force.
    Now on your question, Fc is caused by the material of the plate wanting to retake is original state, so this force will decrease if you give more space to the material, and the tensile force does exactly that. As long as there is the slightiest line between the 2 plates Fc is equal to 0.
    But if the plates don't move at all, I think both forces apply.

    Bolt B: I don't see a situation where the bolt takes compression force. If you compress the plates together, you basically releave the bolt. You're increasing Fc but the reaction force will mostly apply on the aera where you press and not on the bolt. So your answer is basically Fc-Ryc, but it's more complicated than that. the practical answer is "compression is not a problem".
    If you apply your compression directly on the bolt (and only on the bolt) then yes there will be compression, but this compression will apply on the plates and not on the thread between the bolt and the screw, so here again you are helping the bolt. This can only be a problem if you force is huge to the point it deforms the bolt.
    If you apply comrpession on the screw (and only on the screw) then it's the same case as the sketch with Bolt A.

    I hope that was helpful.
    Last edited by Foudzing; 11-27-2015 at 03:47 AM.

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