Difference between plastic and Elasto-plastic deformation

The elasto-plastic behaviour is composed with the elastic behaviour + plastic behaviour.

I less you here the definition given Mendelson1968:

"If one takes a thin strip of a metal such as aluminium and clamps one end and applies a bendig force to the other end, the end of the strip will deflect. Upon removal of this force, if this force is not too large, the end of the strip will spring back to its original position, and there will be no apparent permanent deformation. If a sufficiently large load is applied to the end, the end will not spring back all the way upon the removal of the load but will remain permanently deformed, and we say that plastic flow has occurred."

 So that measn that wen the deformations is not permanent is elastic, bur when it is permanent is plastic.

In a tensile test for example, firstly until yield stress, the deformation is only elastic deformation  epsilon=epsilon(elastic), but one that the yield stress is reached the plastic behaviour becomens in action,and both behaviours elastic and plastic occurs at the same time.So, the deformation produced after yield stress is a elastic-plastic epsilon=epsilon(elastic)+epsilon(plastic). The elastic one is going to "spring back" but the plastic will remains.

In short, the elastic deformations disapeear when the load is removed mut the plastic remains after the load is removed. The elastic+palstic deformations is the sum of both.