Percent Elongation
Calculate the percent elongation, A% = (L_f − L₀) ÷ L₀ × 100%, from the initial gauge length L₀ and the final length L_f measured after rupture in a tensile test (fitting the two halves of the specimen back together). The result, in %, is a direct measure of the material's ductility — how much it stretches before breaking. Ductile steels reach 20–40%; brittle materials, a few percent. Elongation depends on the gauge length used, so it is always quoted with it (e.g. A% over 50 mm). Enter the initial and final lengths.
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Percent elongation
Percent elongation is the most direct and intuitive measure of a material's ductility — how far it can stretch before it breaks. It comes out of the tensile test: a gauge length L₀ is marked on the specimen before loading; after fracture the two halves are fitted back together and the final length L_f between the marks is measured. The elongation is A% = (L_f − L₀) ÷ L₀ × 100%. Ductile materials, such as low-carbon steels and annealed aluminium, stretch 20–40%; brittle materials, such as cast irons and ceramics, fail after almost no deformation (1–2% or less). One detail matters a great deal: elongation depends on the gauge length used, because the deformation concentrates in the necking region — the 'neck' where the specimen thins down just before rupture. In a short specimen that localised deformation weighs heavily on the percentage; in a long one it is diluted over more material. That is why elongation is always quoted together with the gauge — for example, 'A% = 25% in 50 mm'. Comparisons only make sense between values measured over the same gauge length. Enter the initial and final lengths.
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Calculate the true (logarithmic) strain, ε = ln(1 + e), from the engineering strain e (dimensionless or fractional). While engineering strain uses the fixed initial length as reference, true strain integrates the instantaneous length changes, being additive and better suited to large plastic deformations such as in metal forming (rolling, extrusion, drawing). The result is the actual strain accumulated by the material. For small strains, ε ≈ e; the difference grows as strain increases. Enter the engineering strain.
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Calculate a geosynthetic's tensile stiffness (secant stiffness modulus), J = T ÷ ε, from the tensile force per unit width T (kN/m) and the corresponding strain ε (dimensionless, or ε/100 if in %); the result, in kN/m, is the stiffness. Unlike conventional materials, where stiffness is Young's modulus (stress/strain, in Pa), in geosynthetics the 'stress' is expressed per unit WIDTH (kN/m, since thickness is ill-defined and variable), so the stiffness J is also in kN/m. Tensile stiffness is fundamental in soil reinforcement design because geosynthetics only mobilize force when they DEFORM (stretch): the higher the stiffness J, the smaller the deformation needed to reach the required reinforcement force. This is crucial because reinforced-soil structures have ALLOWABLE deformation limits (a wall cannot bulge too much, an embankment cannot settle excessively) — so design is often controlled by stiffness (deformation) rather than strength (rupture). Modern reinforcement geosynthetics (polyester or HDPE geogrids) have high stiffness to limit deformations. Stiffness is measured in the wide-width tensile test, usually at a reference strain (2%, 5%). Enter the tensile force and the strain.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.