Simple Bending Equation
From DT Online
Description
The Simple Bending Equation applies to simply supported beams (and arches if the radius of curvature is greater than 10 times the depth)
Where:
 M = the Maximum Bending Moment
 σ = the Tensile Strength of the material (obtainable from tables or by experiment)
 Capital I = the Moment of Inertia about the Neutral Axis (for a rectangular beam this is its breadth times the depth cubed divided by 12).
 y = the distance of the Neutral Axis from the maximum stress (for a uniform rectangular beam this is half the depth)

Click top left to enlarge 