Can you please have a look at the attached file. I have answered the questions but not sure if they are all right! Any help is greatly appreciated
Yes the curve shows ductile behaviour. Deformation occurs at any point of the curve, not just at A. Point A marks the beginning of permanent set or plasticity. It is called the Elastic Limit or the Limit of Proportionality. Point B marks the Yield Point. Beyond Y the stress decreases with increasing strain and necking occurs. The stress at Y is the ultimate tensile strength. X is the final fracture point. The slope of the curve is the modulus of elasticity. (Youngs Modulus). If the material is stressed beyon the elastic limit at A to point B and then destressed, the material will be work hardened (strain hardened) so that B is now the elstic limit and the new loading curve will follow the right hand dashed line. It will also have acquired a permanent set equal to the difference between the two dashed lines along the strain axis.
Any point between A and Y is a 'Yield Point' It just depends where you get to. 0.002 strain is an arbitrary figure. Read also my last paragraph of post #2 again.