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Homework Help: Stress in a bolt

  1. Oct 27, 2013 #1
    1. The problem statement, all variables and given/known data
    (a) By using either the vector algebra or polygon methods for finding a
    resultant, determine the magnitude of F that will cause the net effect of
    the three forces to act vertically.
    (b) For that value of F, determine the stress in the bolt’s 1-cm diameter
    straight shank.

    2. Relevant equations

    3. The attempt at a solution
    I have found that the sum of the vertical forces are 791.75 N. But I don't know how to calculate the tensile stress in a bolt, is there a special equation to find the area? (sorry i'm new at mechanical engineering :) )
    By the way the answers are: (a) 568.46 N, (b) 10.08 MPa
  2. jcsd
  3. Oct 27, 2013 #2
    I found the answer,
    The cross sectional area is A= (pi*d^2)/4 = 0.00000785398 m^2
    791.75/0.0000785398= 10080876.1927 Pa = 10.08 MPa

    But I don't understand why do we divide the area by 4?
  4. Oct 27, 2013 #3


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    Look up the definition of stress, or even just the units....

    http://en.wikipedia.org/wiki/Stress_(mechanics [Broken])

    Last edited by a moderator: May 6, 2017
  5. Oct 27, 2013 #4


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    The area of a circle is Pi*R^2 or Pi*(D/2)^2 = (Pi*D^2)/4
  6. Oct 27, 2013 #5
    Oh sorry, i didn't realise that it was the diameter, I tried to solve the problem like it was the radius. My bad :) (Sorry for my poor english) The reason i couldn't solve the problem at the first place is i overlooked the word diameter, thanks
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