This document discusses bending moment stress, which is the internal stress caused by bending moments in a beam. It defines bending moment stress and provides the formula to calculate it based on the moment acting, distance from the neutral axis, and moment of inertia. It also discusses uniaxial bending stress, which acts in one direction, and biaxial bending stress, which acts in two directions. Examples of each type are provided to illustrate stress distribution under different loading conditions.