Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Which stress counts when looking at yield

  1. Dec 25, 2014 #1
    To makes things simple, consider a simple beam fixed at one end an a load applied at the other. This load will produce shear stress, bending stress, and torsional stress. When looking at yield at the fixed end, do I take the biggest stress of the three or do I add their magnitudes to see if it exceeds the yield stress of the beam? Also what do I do if I have shear and bending in 2 directions?
  2. jcsd
  3. Dec 25, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    If you have multiple stresses to sort out, the best thing to do is use Mohr's circle to combine them. Bending stresses usually act in the axial direction; shear stresses can occur in different planes. In general, you cannot simply add the magnitudes of stresses together unless they act in the same direction.

  4. Dec 26, 2014 #3
    I thought I could add them using vector addition. If I remember my Mohr's circle correctly, on the circle the maximum stress occurs when shear is 0 and max shear is when stress is 0. So after drawing the circle and finding the maximum stress and shear I look at them individually to see if either exceeds the yield stress, which I assume is different in normal and shearing conditions. Is my reasoning correct?
  5. Dec 26, 2014 #4
  6. Dec 26, 2014 #5
    I had completely forgotten about that. That should solve my problem, thank you for helping.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook