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Bending force or shear force what's the difference?

  1. Sep 29, 2015 #1
    Hi today I was watching a demonstration of using explosives in demolition and emergency rescue and they did one where they wrapped explosive cord around a steel I beam and cut it in half then said this was a shearing force which sounded right to me but then they took a concrete post similar shape to the I beam and packed one side of the I with plastic explosive placed a metal plate over it and secured in place with tape and said this is also a shearing force... But surely under this circumstanc it would be a bending force that breaks the post??

    Put after consideration it dawned on me that a bending force and a shearing force are the same thing in a way so what's what and what's the difference?? Thanks guys
    S
     
  2. jcsd
  3. Sep 30, 2015 #2
    A shearing force is something that causes a shearing deformation: the angle changes between two perpendicular sides of a body.

    A bending force is something that causes a bending deformation: the angle changes between two internal faces of a body.
     
  4. Sep 30, 2015 #3

    Mech_Engineer

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    Bending creates a combination of tension and compression through the thickness of the bending part; where as shear stress would be an "orthogonal" stress caused by a shearing force. Imagine bending a strip of sheet metal (bending) vs. cutting it with scissors (shear).

    Wikipedia has some pretty good articles on the subject it might be the diagrams will help you visualize the difference:
    https://en.wikipedia.org/wiki/Bending
    https://en.wikipedia.org/wiki/Shear_stress
     
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