• id: JME-08-N10
• title: Stress-Strain Curve for Ductile Metals
• tags: stress-strain, yield, ultimate-strength, fracture

The stress-strain curve for a ductile metal (e.g., mild steel) has distinct regions: (1) Linear elastic region (O to proportional limit) — Hooke's law valid, slope = $Y$. (2) Non-linear elastic region (to elastic limit) — still recoverable but not linear. (3) Yield region — upper and lower yield points; plastic deformation begins. (4) Strain hardening — stress increases with strain as dislocations pile up. (5) Ultimate tensile strength (UTS) — maximum stress; necking begins. (6) Fracture point — material breaks. Brittle materials (cast iron, glass) fracture soon after the elastic limit with little plastic deformation.