Bending equation:

$\frac{M}{I} = \frac{\sigma}{y} = \frac{E}{R}$

Where, E = Modulus of Elasticity of beam material

R = Radius of Curvature of the beam

M = Moment of resistance

I = Moment of Inertia of beam c/s about N.A

$\sigma$ = Bending stress at the layer situated at a distance y from N.A

y = Distance of layer from N.A.