A thin-walled hollow tube AB of conical shape has constant thickness t and average diameters d A and d B at the ends (see figure). (a) Determine the strain energy U of the tube when it is subjected to...

A thin-walled hollow tube AB of conical shape has constant thickness t and average diameters d_A
and d_B
at the ends (see figure).

(a) Determine the strain energy U of the tube when it is subjected to pure torsion by torques T.

(b) Determine the angle of twist ϕ of the tube.