The following assumptions are made in simple theory of bending:
1. The beam is initially straight and every layer of it is free to expand or contract.
2. The material is homogeneous and isotropic.
3. Young's Modulus is same in tension and compression.
4. Stresses are within elastic limit .
6 Plane section remains plane even after bending
6. The radius of curvature is large compared to depth of beam