Simple Bending or Pure Bending:- A beam or cantilever is said to be subjected to simple bending or pure bending when it bends under the action of uniform bending moment, without any shear force.

 

Assumptions in pure bending theory: The assumptions made in the theory of simple bending are as follows:
• The material of the beam is perfectly homogeneous and isotropic.
• The material is stressed within elastic limit and obeys Hooke's law.
• The value of the modulus of elasticity for the material is same in tension and compression.
• The beam is subjected to pure bending and therefore bends in the form of an arc of a circle.
• The radius of curvature of the bent axis of the beam is large compared to the dimensions of the section of beam.
• The transverse sections, which are plane and normal to the longitudinal axis before bending remain plane and normal to the longitudinal axis of the beam after bending.
• The stresses are purely longitudinal and local effects of concentrated loads are neglected..