ISO 10113:2020 pdf download – Metallic materials – Sheet and strip – Determination of plastic strain ratio
6 Test equipment
The tensile testing machine used shall comply with the requirements of ISO 6892-1. For the manual method (see 8.2), the device for the measurement of the original gauge length and the gauge length after plastic straining and unloading shall be capable of measuring with an accuracy of ±0,2 % or better. The device used for determining the original width and the gauge width of the test piece after plastic straining and unloading shall be capable of measuring with an accuracy of ±0,005 mm or better. For the semi-automatic method (see 8.3), an extensometer for length measurement in accordance with ISO 9513, of class 1 or better, shall be used. The device used for determining the original width and the gauge width of the test piece after plastic straining and unloading shall be capable of measuring with an accuracy of ±0,005 mm or better. For the automatic method (see 8.4), extensometers in accordance with ISO 9513, of class 1 or better in the relevant strain range, shall be used. The device used for determining the original width shall be capable of measuring with an accuracy of ±0,1 % or better. NOTE When using a long gauge length and large extensions are applied, the maximum error of the class 1 extensometer can be greater than ±0,01 mm. The method of gripping the test piece shall be as specified in ISO 6892-1.
7 Test piece
The test piece shall be taken in accordance with the requirements of the relevant product standard or, if not specified therein, as agreed between the parties involved. The type of the test piece and its preparation, including machining tolerances, the tolerances on shape and the marking of the original gauge length, shall be as defined in ISO 6892-1:2019, Annex B. In addition, within the gauge length the edges shall be sufficiently parallel that two width measurements do not differ by more than 0,1 % of the mean of all the width measurements. To reach a homogeneous strain distribution in the gauge length for all types of test pieces (ISO 6892-1:2019, Annex B), the parallel length L c shall be equal to or larger than (L o + 2 bo ). The test piece thickness shall be the full sheet thickness, unless otherwise specified. The parallel length of the test piece shall be free of surface defects (e.g. scratches).
8.1 General
In general, tests are carried out at ambient temperature between 10 °C and 35 °C. Tests carried out under controlled conditions, where required, shall be made at a temperature of (23 ± 5) °C. In the range of evaluation, the strain rate of the parallel length shall be constant with a relative tolerance of ±20 % and not exceed 0,008/s. Any strain rate changes should be finished at least 0,2 % strain before the start of the range of evaluation. NOTE In the case of coated material (e.g. galvanised or with organic coatings), the r-values obtained can differ from those of base material without coating. If, after the test, the test piece shows transverse bow (see Figure 2), the test shall be considered invalid, and a new test shall be carried out, because the test results could be influenced.