Tensile Testing —
Strength, Yield & Deformation

Ultimate tensile strength — the maximum load per unit original cross-sectional area before fracture. The primary acceptance criterion in most material specifications.

The stress at which the material transitions from elastic to plastic behaviour. Reported as upper yield point (UYP) and lower yield point (LYP) for mild steel with a pronounced yield phenomenon.

Stress at 0.2% plastic strain offset — the universally adopted yield point for non-ferrous alloys, austenitic and duplex stainless steels, and high-strength steels without a distinct yield point.

Stress at 0.5% total extension under load (Rt0.5). Required by certain IS and EN material standards for austenitic stainless grades.

Stress at 1% total extension. Specified for particular product categories in some Indian Standards.

Percentage increase in gauge length at fracture, measured on the standard proportional gauge length (5.65√A₀ or 4d). The primary ductility indicator for structural safety and formability assessment.

Percentage reduction in cross-sectional area at the fracture location. A sensitive indicator of through-thickness ductility, particularly relevant for bars, rods, and fastener wire.

Ductility and surface soundness assessment when the specimen is bent through a specified angle over a mandrel of prescribed diameter. Detects surface and near-surface defects invisible to the tensile test.

Mandatory for Fe 415/500/550/600 grade TMT reinforcement bars. Specimen bent 45°, aged at 100°C for 30 min, then re-bent in the reverse direction. Evaluates susceptibility to strain-ageing embrittlement.

Compressive yield strength and deformation behaviour under axial compressive loading. Applied to castings, bearing materials, and brittle materials where tensile testing is impractical.

Ductility test specific to seamless and welded tube and pipe products. Evaluates the ability of the tube end to be flared outward or flanged at 90° without cracking.