Annex H (informative) Manual method of determination of percentage total elongation at maximum force for long products such as bars, wire, rods

The extensometer method defined in clause 12 may be replaced by the following manual method. In case of dispute, the extensometer method shall be used.

The method consists of measuring, on the longer part of a test piece which has been submitted to a tensile test, the non-proportional elongation at maximum force, from which the percentage total elongation is calculated.

Before the test, equidistant marks are made on the measuring gauge length, the distance between 2 successive marks being equal to a submultiple of the initial gauge length ( $L_{\mathrm{o}}^{\prime}$ ). The marking of the initial gauge length ( $L_{\mathrm{o}}^{\prime}$ ) should be accurate to within ± 0,5 mm. This length which is a function of the value of the percentage total elongation should be defined in the product standard.

The measurement of the final gauge length after fracture (L'u) is made on the longest broken part of the test piece and should be accurate to within 0,5 mm.

In order that the measurement is valid, the two following conditions should be respected:

• the limits of the measuring zone should be located at least 5 d from the fracture section and at least 2,5 d from the grip;
• the measuring gauge length should be at least equal to the value specified in the product standard.

The percentage non-proportional elongation at maximum force is calculated by the following formula:

$A_{\mathrm{g}}=\frac{L_{\mathrm{u}}^{\prime}-L_{\mathrm{o}}^{\prime}}{L_{\mathrm{o}}^{\prime}} \times 100$

The percentage total elongation at maximum force is calculated by the following formula:

$A_{\mathrm{gt}}=A_{\mathrm{g}}+\frac{R_{\mathrm{m}}}{E} \times 100$