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Homework Help: Mechanics: Eccentric torsion + non circular tube

  1. Nov 4, 2008 #1
    dear all, i have just received a question about torsion.

    1. The problem statement, all variables and given/known data
    *************** a graph has been attached as attachment at bottom*************

    The objective is to find the torsion shear stress at the cross section of the "dark Grey tube".

    Let's have a look:
    1.There is a reaction torque acting on the motor M,
    2.The force is then transfered to dark grey tube by a light grey carrier.
    3. blue cross is the center of the motor
    4. purple cross is the centroid of the dark grey tube
    5. i have J / Ixx,Iyy of that tube
    6. Only the dark grey tube is fixed at 2 ends.
    7. carrier is mush shorter than the tube

    2. Relevant equations

    I think I am finding the suitable eqts. So I miss this section.
    You think T/J= shear/R ??

    3. The attempt at a solution

    #1 i would like to ask whether the following steps are correct
    #2 What is the torsion equations for irregular hollow section.
    #3 how to find the R, outer radius of the shaft, for the case that equation T/J= shear/R is used.

    My Methodology:
    1. Shear force is acting at the 2 hand sides of the tube as resultant.
    2. the Shear force acts like a torque on the hollow section
    3. use parallel axis theorem to transform "moment of inertia" from the original centroid to the torque center
    4. use a torsion equation that contain J to fix it (<------------#2 that's what i would like to find now)

    Thank you very much for your help.

    Attached Files:

    Last edited: Nov 4, 2008
  2. jcsd
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