please explain the concept of Torsion rigidity giving examples.
If a round bar is twisted, it resists being twisted because it has torsional rigidity.
If the length of the bar is L, the applied torque is T, the angle of twist is phi, the area moment of inertia of the circular section is J, and the shear modulus of the material is G, then these variables are related by the linear elastic relation
phi = (T*L)/(J*G)
The torsional stiffness would then be
Kt = J*G/L
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