Typical points of interest when tensile testing a material include:
ultimate tensile strength or peak stress; modulus of elasticity, offset yield strength, which represents a point just beyond the onset of permanent deformation; and elongation at break.
The modulus of elasticity is calculated as the slope in the linear elastic region of the stress-strain curve. The linear elastic region is prior to the proportional limit (see point A - Figure 1). Beyond the proportional limit, the material undergoes permanent plastic deformation.