Calculate the value of G for brass, if the angle of twist over a length of 1 meter is $7.2^\circ$, when the compound bar is subjected to a twisting couple 520 N-m. Also calculate the maximum shear stress in both the material if $G_s= 80 Mpa$.

For composite bar

$\theta = \theta_B = \theta_S\\ T = T_B + T_S$

$\theta = 7.2^\circ = 0.1256\hspace{0.05cm}rad\\ \theta_B = \theta_S = 0.1256\\ T = 520\hspace{0.05cm}Nm = 520\hspace{0.05cm}\times\hspace{0.05cm}10^3\hspace{0.05cm}Nmm\\ J = \frac{\pi}{32}[D^4 - d^4]\\ \hspace{0.25cm} = \frac{\pi}{32}[32^4 - 19^4]\\ J = 90.14\hspace{0.05cm}\times\hspace{0.05cm}10^3\hspace{0.05cm}mm^4\\ R = \frac{D}{2} = 16\hspace{0.05cm}mm$

$\frac{T}{J} = \frac{G\theta}{L}\\ T …