Which of the following assumptions are True for torsion theory for axisymmetric sections?

Different assumptions made in torsion theory are as follows:

1) Shaft must be straight and should have a uniform cross-section.

2) The shear stress induced in the shaft should not exceed the elastic limit.

3) Twist along the shaft is uniform.

4) The material is homogenous and isotropic.

5) Circular Sections before twisting remain circular even after twisting.

6) Plane sections before twisting remain plane after twisting.

Important Points

Torsion equation for circular cross-section is given as,

\(\frac{{\rm{T}}}{{\rm{J}}} = \frac{{{{\rm{τ }}_{{\rm{max}}}}}}{{\rm{R}}} = \frac{{{\rm{Gθ }}}}{{\rm{L}}}\)

where, T = torque, J = Polar moment of inertia, τmax = maximum shear stress, R = radius of circle, G =  Modulus of rigidity, θ  = angle of twist, L = length of bar/rod