BS EN ISO 3376-2020 pdf free download.Leather – Physical and mechanical tests – Determination of tensile strength and percentage elongation
This document specifies a method for determining the tensile strength, elongation at a specified load and elongation at maximum force of leather. It is applicable to all types of leather.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2418, Leather — Chemical, physical and mechanical and fastness tests — Sampling location
ISO 2419, Leather — Physical and mechanical tests — Sample preparation and conditioning
ISO 2589, Leather — Physical and mechanical tests — Determination of thickness
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:Tension/compression testing machines — Calibration and verification of the force-measuring system
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia. available at http:// www .electropedia .org/
4 Principle
A test piece is extended at a specified rate until the forces reach a predetermined value or until the test piece breaks.
5 Apparatus
5.1 Tensile testing machine, with:
a) a force range appropriate to the specimen under test;
b) a means of recording the force to an accuracy of at least 2 % as specified by Class 2 of ISO 7500-1;
c) a uniform speed of separation of the jaws of 100 mm/min ± 20 mm/min;
d) a means of recording the force, for example as an elongation curve;
e) jaws, minimum length of 45 mm in the direction of the applied load, designed to apply constant clamping by mechanical or pneumatic means. The texture and design of the inside faces of the jaws shall be such that, at the maximum load attained in the test, the specimen does not slip in either jaw by an amount exceeding 1 % of the original jaw separation.
5.2 A means of determining the elongation of the test piece, either by monitoring the separation of the jaws or by sensors which monitor the separation of two fixed points on the test piece.
5.3 Thickness gauge, as specified in ISO 2589.
5.4 Press knives, as specified in ISO 2419, capable of cutting a standard or large size test piece as shown in Figure 1 to the dimensions given in Table 1.
5.5 Vernier callipers, reading to 0,1 mm.
6 Sampling and sample preparation
6.1 Sample in accordance with ISO 2418.
6.2 After conditioning in accordance with ISO 2419, cut six test pieces from the sample by applying a press knife (5.4) to the grain surface, three test pieces with the longer sides parallel to the backbone and three test pieces with the longer sides perpendicular to the backbone. If previous testing has shown that there is slippage of the test piece in the jaws, use the large press knife (5.4).
If there is a requirement for more than two hides or skins to be tested in one batch, then only one test piece in each direction need be taken from each hide or skin, provided that the overall total is not less than three test pieces in each direction.
6.3 If the test pieces are removed from standard atmosphere for cutting and not tested within 30 minutes, then the test pieces shall be returned straight away to the standard atmosphere for conditioning in accordance with ISO 2419. 7 Procedure
7.1 Determination of dimensions
7.1.1 Using vernier callipers (5.5), measure the width of each test piece to the nearest 0,1 mm at three positions on the grain side and three on the flesh side. In each group of three measurements, make one at the mid-point E (as shown in Figure 1) and the other two at positions approximately midway between the mid-point E and the lines AB and CD. Take the arithmetic mean of the six measurements as the width of the test piece, w. For soft (flexible) leather, the width b (in Figure 1) shall be taken as the width of the press knife.
7.1.2 Measure the thickness of each test piece in accordance with ISO 2589. Make the measurements at three positions, namely the mid-point E and at positions approximately midway between the mid- point E and the lines AB and CD. Take the arithmetic mean of the three measurements as the thickness of the test piece, t.
7.2 Determination of tensile strength
7.2.1 If 7.3 and/or 7.4 are also required to be carried out, then the same test piece may be used to complete 7.2, 7.3 and/or 7.4 in a single test, providing the pre-load and initial length measurement described in 7.3.1 is carried out at 7.2.1.
7.2.2 Set the jaws of the tensile testing apparatus (5.1) (50 ± 1) mm apart if using the standard test piece or (100 ± 1) mm apart if using the large test piece. Clamp the test piece in the jaws so that the edges of the jaws lie along the lines AB and CD. When the test piece is clamped, ensure its grain surface lies in one plane. The length axis shall be parallel to the traction direction.
7.2.3 Run the machine until the test piece breaks and record the highest force exerted as maximum force, F max .
7.2.4 For tensile strength determination, the recorded F max value shall be used for calculation. NOTE Variable results can occur if using the force at the test piece’s break, F break , instead of F max , depending on the type of leather.BS EN ISO 3376 pdf download