Gere & Goodno — Torsion: Problem 3.11-3

3.11-3 A thin-walled aluminum tube of rectangular cross section (see figure) has a centerline dimensions \( b = 50 \text{ mm} \) and \( h = 20 \text{ mm} \). The wall thickness \( t \) is constant and equal to \( 3 \text{ mm} \). (a) Determine the shear stress in the tube due to a torque \( T = 90 \text{ N}\cdot\text{m} \). (b) Determine the angle of twist (in degrees) if the length \( L \) of the tube is \( 0.25 \text{ m} \) and the shear modulus \( G \) is \( 26 \text{ GPa} \).