BS ISO 37:2017pdf free download.Rubber, vulcanized or thermoplastic – Determination of tensile stress-strain properties.
This document specifies a method for the determination of the tensile stress-strain properties of vulcanized and thermoplastic rubbers.
The properties which can be determined are tensile strength, elongation at break, stress at a given elongation, elongation at a given stress, stress at yield and elongation at yield. The measurement of stress and strain at yield applies only to some thermoplastic rubbers and certain other compounds.
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 5893 , Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of traverse) — Specfication.
ISO 23529:2016, Rubber — General procedures for preparing and conditioning test pieces for physical test methods.
4 Principle
Standard test pieces, either dumb-bells or rings, are stretched in a tensile-testing machine at a constant rate of traverse of the driven grip or pulley. Readings of force and elongation are taken as required during the uninterrupted stretching of the test piece and when it breaks.
5 General
Dumb-bell and ring test pieces do not necessarily give the same values for their respective stress-strain properties. This is mainly because in stretched rings, the stress is not uniform over the cross-section. A second factor is in the existence of “grain” which might cause dumb-bells to give different values depending on whether their length is parallel or at right angles to the grain.
The main points to be noted in choosing between rings and dumb-bells are as follows.
a) Tensile strength
Dumb-bells are preferable for determination of tensile strength. Rings give lower, sometimes much lower, values than dumb-bells.
b) Elongation at break
Rings give approximately the same values as dumb-bells, provided that
1) the elongation of rings is calculated as a percentage of the initial internal circumference, and
2) dumb-bells are cut at right angles to the grain if this is present to a significant degree.
Dumb-bells shall be used if it is required to study grain effects, as rings are not suitable for this purpose.
c) Elongation at a given stress and stress at a given elongation
The larger dumb-bells (types 1, 2 and 1A) are generally preferred.
6 Test pieces
6.1 General
Miniature test pieces might give somewhat different, usually higher, values for tensile strength and elongation at break than the larger test pieces.
Seven types of test piece are provided, i.e. dumb-hell-shaped types 1, 2, 3, 4 and 1A and ring-shaped types A (normal) and B (miniature). The results obtained for a given material are likely to vary according to the type of test piece used. Therefore, the results obtained for different materials should not be regarded as comparable unless the same type of test piece has been used.
When preparation of test pieces requires buffing or thickness adjustment, results might be affected.