Why shear stress is produce in shafts

[adilgrt007]

hi my name is adil from Pakistan.what is a reason to produce shear stress in shaft,can normal stresses is produced in shaft&where is max shear stress is apply in solid shaft at end or center.

 

[Mech_Engineer]

If a moment is applied to a shaft to create torsion, there is shear stress in the material which is greatest at the outer surface and zero at the center.

http://en.wikipedia.org/wiki/Torsion_(mechanics )

 

[adilgrt007]

thanks for answer but why shear stress is zero at center and max at point?

 

[256bits]

When a shaft is twisted, does not the outer surface twist the most. The strain is proportional to the radius, so the centre has 0 stress and the outer edge has the most stress.