A cyiindrical elastic body subjected to pure torsion about

1. tensile stress in a direction 45° to the axis
2. no tensile or compressive stress
3. maximum shear stress along the axis of the shaft
4. maximum shear stress at 45° to the axis

Pure torsion σ_x = σ_y = 0, τ_xy = τ
principle stress

σ_{1 , 2} =	σ_x + σ_y	± √			σ_x - σ_y		²	+ τ²_xy
	2				2

σ_{1 , 2} = ± τ_xy
So, angle of maximum principle stress

tan(2θ_p) =	2τ_xy	= ∞
	σ_x - σ_y

2θ_p =	π
	2

θ_p =	π	or 45°
	4