no twisting, buckling or crippling occurs.if the material has different strengths in tension and compression (example cast iron or other anisotropic materials) then separate calculations are required for both tension and compression surfaces.the beam material is homogeneous and has equal strength in tension and compression.the resulting stress is below the limit of proportionality of the material.all the loads act perpendicular to the longitudinal axis of the beam.the beam is straight, relatively long and narrow and of uniform cross-section.The flexure formula is valid if the following criteria are met: Z x is called section modulus and is a term that combines the moment of inertia and the distance to the extreme fiber ( Z x = I x / c).c is the maximum distance from the centroidal axis to the extreme fiber (again, this can be to the top or bottom of the shape).I x is the moment of inertia about x (horizontal) centroidal axis.if the maximum bending stress is required then M is the maximum bending moment acting on the beam.M is the bending moment along the length of the beam where the stress is calculated.σ max is the maximum stress at the farthest surface from the neutral axis (it can be top or bottom).To determine the maximum stress due to bending the flexure formula is used:
