Plastic bending

Note that the deflections necessary to develop the stresses indicated in a plastic analysis are generally excessive, frequently to the point of incompatibility with the function of the structure.

Plastic bending begins when an applied moment causes the outside fibers of a cross-section to exceed the material's yield strength.

Rather, outside regions will yield first, redistributing stress and delaying failure beyond what would be predicted by elastic analytical methods.

The stress distribution from the neutral axis is the same as the shape of the stress-strain curve of the material (this assumes a non-composite cross-section).

In the elastic region of the cross-section, the stress distribution varies linearly from the neutral axis to the beginning of the yielded area.

Predicted failure occurs when the stress distribution approximates the material's stress-strain curve.