Figure 4 Typical Brittle Material Stress-Strain Curve

STRESS-STRAIN RELATIONSHIP DOE-HDBK-1017/1-93 Properties of Metals The area between Points 1 and 2 is called the elastic region. If stress is removed, the material will return to its original length. Point 2 is the proportional limit (PL) or elastic limit, and Point 3 is the yield strength (YS) or yield point. The area between Points 2 and 5 is known as the plastic region because the material will not return to its original length. Point 4 is the point of ultimate strength and Point 5 is the fracture point at which failure of the material occurs. Figure 3 is a stress-strain curve typical of a Figure 4 Typical Brittle Material Stress-Strain Curve ductile material where the strength is small, and the plastic region is great. The material will bear more strain (deformation) before fracture. Figure 4 is a stress-strain curve typical of a brittle material where the plastic region is small and the strength of the material is high. The tensile test supplies three descriptive facts about a material. These are the stress at which observable plastic deformation or "yielding" begins; the ultimate tensile strength or maximum intensity of load that can be carried in tension; and the percent elongation or strain (the amount the material will stretch) and the accompanying percent reduction of the cross-sectional area caused by stretching. The rupture or fracture point can also be determined. MS-02 Page 18 Rev. 0