Answer:
initially there is the linear elastic region which obeys the hooks law :stress is directly proportional to the strain.
at the end of the linear elastic region the ductile material reaches the yield point beyond which any change in dimensions become permanent. the material goes through a yield plateau in which stress is constant and the strain changes.
after crossing the yield plateau the ductile material goes through the strain hardening region in which the deformation is permanent but as the region goes on the stress increases with the strain. here the strength of the ductile material increases as it is strain hardened. at a point it reaches the ultimate load point. This is the maximum load taken by the material. after which further deformation causes decrease in strength or the stress goes on decreasing finally breaking at the breaking load point. this region is called the post-ultimate region.