ISO 527-1:2019 pdf free.Plastics – Determination of tensile properties-General principles.
4 Principle and methods
4.1 Principle
The test specimen is extended along its major longitudinal axis at a constant test speed until the specimen fractures or until the stress (load) or the strain (elongation) reaches some predetermined value. During this procedure, the load sustained by the specimen and the elongation are measured.
4.2 Method
4.2.1 The methods are applied using specimens which may be either moulded to the chosen dimensions or machined, cut or punched from finished and semi-finished products, such as mouldings, laminates, films and extruded or cast sheet. The types of test specimen and their preparation are described in the relevant part of ISO 527 typical for the material. In some cases, a multipurpose test specimen may be used. Multipurpose and miniaturized test specimens are described in ISO 20753.
4.2.2 The methods specify preferred dimensions for the test specimens. Tests which are carried out on specimens of different dimensions, or on specimens which are prepared under different conditions, may produce results which are not comparable. Other factors, such as the speed of testing and the conditioning of the specimens, can also influence the results. Consequently, when comparative data are required, these factors shall be carefully controlled and recorded.
5.1.3 Grips
Grips for holding the test specimen shall be attached to the machine so that the major axis of the test specimen coincides with the direction of extension through the centre line of the grip assembly. The test specimen shall be held such that slip relative to the gripping jaws is prevented. The gripping system shall not cause premature fracture at the jaws or squashing of the specimen in the grips.
For the determination of the tensile modulus, it is essential that the strain rate is constant and does not change, for example, due to motion in the grips. This is important especially if wedge action grips are used.
5.1.4 Force indicator
The force measurement system shall comply with class 1 as defined in Iso 7500-1.
5.1.5 Strain indicator
5.1.5.1 Extensometers
Contact extensometers shall comply with ISO 9513, class 1. The accuracy of this class shall be attained in the strain range over which measurements are being made. Non-contact extensometers may also be used, provided they meet the same accuracy requirements.
The extensometer shall be capable of determining the change in the gauge length of the test specimen at any time during the test. It is desirable, but not essential, that the instrument should record this change automatically. The instrument shall be essentially free of inertia lag at the specified speed of testing.
For the determination of tensile modulus, the instrument shall be capable of measuring the change in the gauge length of the specimen with an accuracy of 1 % of the relevant value or better for all gauge lengths of 50 mm or higher, corresponding to a requirement of absolute accuracy of ±1 l.lm for a gauge length of 50 mm and to ±1,5 urn, in case a gauge length of 75 mm is used.
For smaller gauge lengths between 20 mm and 50 mm an absolute accuracy of ±1 uim is sufficient (see Figure 2 and Annex C.)
NOTE Depending on the gauge length used, the accuracy requirement of 1 % translates to different absolute accuracies for the determination of the elongation within the gauge length. The constant absolute accuracy for the measurement of change in gauge length leads to relative accuracies of 2 % for gauge length 25 mm and of 2,5 % for gauge length 20 mm (see Figure 2).
ISO 527-1 pdf download.