A solid circular shaft of diameter d is subjected to a combined

A solid circular shaft of diameter d is subjected to a combined bending moment M and torque, T. The material property to be used for designing the shaft using the relation
16 √M² + T² is
πd³

1. ultimate tensile strength (S_u)
2. tensile yield strength (S_y)
3. torsional yield strength (S_sy)
4. endurance strength (S_e)

For a circular shaft of diameter d,

T '	=	τ
J	=	(d/2)

where, T ' = net torsional moment
τ = shear stress (torsional shear strength)
J = polar moment of inertia

∴ t =	T '(d/2)
	J

But for a solid circular shaft

J =	π	d⁴
	32

∴ τ =	16T '
	32

But T ' = √M² + T²

∴ τ =	16T '	√M² + T²
	πd³