Explain the engineering stress strain graph mild steel

Elastic Region: Initially, stress is directly proportional to strain (Hooke's Law). If the load is removed, the steel returns to its original shape. The proportional limit and elastic limit are within this region.

Yielding: Beyond the elastic limit, the steel enters the plastic region. It reaches the yield point where it deforms permanently without a significant increase in stress. Mild steel exhibits upper and lower yield points.

Strain Hardening: After yielding, the stress required to continue deformation increases. This is strain hardening or work hardening. The ultimate tensile strength (UTS) is the maximum stress the material can withstand.

Necking and Fracture: Beyond the UTS, the steel begins to neck (reduce its cross-sectional area) and eventually fractures. The stress at fracture is the fracture strength.