How do yield stress, ultimate tensile stress, and elongation describe a metal's mechanical properties?

In materials testing, yield stress, ultimate tensile stress (UTS), and elongation are fundamental metrics used to characterize the mechanical behavior of metals under load. These properties are typically determined through a tensile test, where a sample is subjected to an increasing load until it ruptures.12

• Yield Stress: This is the minimum stress at which a metal transitions from elastic to plastic behavior. Below this point, the material will return to its original shape if the load is removed; above it, the metal undergoes permanent, nonreversible deformation. It is a critical design parameter, as it indicates the load limit before a structure becomes permanently bent or damaged.231
• Ultimate Tensile Stress (UTS): This represents the maximum stress a material can withstand before it breaks. During a test, it is calculated as the maximum load reached divided by the original cross-sectional area of the sample.21
• Elongation: This measures the metal's ductility, defined as the final length of the sample after fracture minus its initial length, divided by the initial length. It quantifies how much a material can deform before failing.14