Question

Strain energy stored in the material when it is subjected to torsional stress

Answer 1

strain energy stored in the material when it is subjected to torsional is given by,
$U=\frac{\tau^2}{4E}\times V$

where, V is the volume of cylinderical shaft.

τ = Shear stress acting at outer surface of shaft i.e. at radius R

E = Modulus of rigidity

U = Strain energy stored in the shaft due to torsion.

here you should know, strain = change in length/original length.

stress = force per unit area.

and modulus of elasticity = stress/strain