Torsion Members under Loading         

 

Typical axial members with applied torque, T  (double headed arrow).  Point the thumb

on your right hand in the direction of the double-headed arrow.  Your fingers show the

direction of the applied torque, T.

 

                           

 

 

In a Nut Shell:  Shear Stress in an Torsion Member

 

The shear stress. τ, in a torsion member (under the assumptions that each circular cross-section

remains plane, perpendicular to its axis, and for elastic response,  τ = G γ  ) is given by the

expression  

  

  τ  =  T ρ / J

 

     τmax  =  T c / J

 

 

where  T is the torque acting on the member at the location where the shear stress is to be

calculated, ρ is the radial distance from the centroidal axis to the “fiber” where the

shear stress is calculated,  J is the polar moment of inertia of the entire cross-section, and  c 

is the radius of the cross-section.  The shear stress is zero on the axis of the member and

maximum at  the outer fiber (outer radius, c) and varies linearly for elastic response.

 

Click here for notes on calculating the polar moment of inertia, J.

 

Common units for shear stress are  psi,  ksi,    MPa, N/mm2  (English/Metric)

 

 

         Click here for examples.

 



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