11Determination of percentage elongation after fracture (A)

IS 1608:2005, Metallic Materials — Tensile Testing at Ambient Temperature

Last Updated 29 Oct 2026

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11.1

Percentage elongation after fracture shall be determined in accordance with the definition given in 4.4.2.

For this purpose, the two broken pieces of the test piece are carefully fitted back together so that their axes lie in a straight line.

Special precautions shall be taken to ensure proper contact between the broken parts of the test piece when measuring the final gauge length. This is particularly important in the case of test pieces of small cross-section and test pieces having low elongation values.

Elongation after fracture ( $L_{\mathrm{u}}-L_{\mathrm{o}}$ ) shall be determined to the nearest 0,25 mm with a measuring device with 0,1 mm resolution and the value of percentage elongation after fracture shall be rounded to the nearest 0,5 %. If the specified minimum percentage elongation is less than 5 %, it is recommended that special precautions be taken when determining elongation (see annex E).

This measurement is, in principle, valid only if the distance between the fracture and the nearest gauge mark is no less than one third of the original gauge length ( $L_{o}$ ). However, the measurement is valid, irrespective of the position of the fracture, if the percentage elongation after fracture is equal to or greater than the specified value.

11.2

For machines capable of measuring extension at fracture using an extensometer, it is not necessary to mark the gauge lengths. The elongation is measured as the total extension at fracture, and it is therefore necessary to deduct the elastic extension in order to obtain percentage elongation after fracture.

In principle, this measurement is only valid if fracture occurs within the extensometer gauge length ( $L_{\mathrm{e}}$ ). The measurement is valid regardless of the position of the fracture cross-section if the percentage elongation after fracture is equal to or greater than the specified value.

NOTE — If the product standard specifies the determination of percentage elongation after rupture for a given gauge length, the extensometer gauge length shall be equal to this length.

11.3

If elongation is measured over a given fixed length, it can be converted to proportional gauge length, using conversion formulae or tables as agreed before the commencement of testing (for example as in ISO 2566-1 and ISO 2566-2).

NOTE — Comparisons of percentage elongation are possible only when the gauge length or extensometer gauge length, the shape and area of the cross-section are the same or when the coefficient of proportionality (k) is the same.

11.4

In order to avoid having to reject test pieces in which fracture may occur outside the limits specified in 11.1, the method based on the subdivision of $L_{\mathrm{o}}$ into $N$ equal parts may be used, as described in annex G.