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Homework Help: Cross section and torque- please help

  1. Dec 21, 2009 #1
    A 3.5 m long steel member with a W310 x 143 cross- section is subjected to 4.5KNm torque. Knowing that G=77GPa, determine (a) the maximum shearing stress along the line a-a, (b) the maximum shearing stress along the line b-b, (c) the angle of twist

    http://lh4.ggpht.com/_H4Iz7SmBrbk/Sysfg6WJmLI/AAAAAAAACBI/SsE4jsJMYAE/22.jpg [Broken]

    i know that


    while Jeq=[tex]\frac{1}{3}[/tex][tex]\sum[/tex]hibi3

    Jeq=1/3*((0.309*0.02293) +(0.309*0.02293) + (0.2872*0.0143))








    = 2.3022e7

    (according to my book the correct answers are meant to be 39.7MPa and 24.2MPa)

    for the angle




    = 3.3199 degrees,

    but again the correct answer is meant to be 4.72 degrees,

    what am i doing wrong??
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 22, 2009 #2
    i think i need to SOMEHOW find the torque seperately on the flange and web and them somehow solve the problem,, please help someone
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