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Torsion problem finding d!

  1. Dec 1, 2009 #1
    Hello I recently got handed this problem and I had a fair idea on how to go about it or so I thought! My only problem is I do not know how to find d? I would be grateful if someone could show me how to find d and show me the equation used

    Thank you

    1. The problem statement, all variables and given/known data

    A steel shaft 3m long is transmitting 1MW at 240rev/min. The working conditions to
    be satisfied by the shaft are:

    (a) that the shaft must not twist more than 0.02radian on a length of 10 diameters;

    (b) that the working stress must not exceed 60MN/m2.

    If the modulus of rigidity of the steel 80GN/m2 what is

    (i). the diameter of the shaft required;

    (ii). the actual working stress;

    (iii). the angle of twist of the 3m length?


    2. Relevant equations

    T/J=Gxtheta/L=t/R
    T=power/W
    rads=degrees x pi/180

    3. The attempt at a solution

    (1x106) /(240/2pi/60)= T = 39.793KN

    J= pi x d4/32
    diameter=d
    T= Torque
    G =mod of rigidity
    J= polar second moment of area???
    R= radius

    d=?????


    G=80x109

    G x theta (0.02) = 1.6x109/10d

    what is the diameter??? and how would i go about finding it???

    thanks
     
    Last edited: Dec 1, 2009
  2. jcsd
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