Which portions of the loaded beam shown in the given figure is subjected to pure bending?

Explanation:

In Simple bending or Pure bending

• Bending Moment is constant along the length of the beam i.e. 
• Shear force is zero.

The SFD and BMD diagram for the above beam will be like

From the diagram we can see that SF = 0 and BM = constant between BD, Hence in Pure bending.

Equation of Pure Bending:

where,

M = Bending Moment

σ = Bending stress at a distance y from NA

I = MOI of cross - section about NA

E = Young's Modulus of Elasticity

1/R = Curvature