ISO 37:2011 pdf download – Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties.
1 Scope This International Standard describes 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 referenced documents are indispensable for the application 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) — Specification ISO 23529:2010, Rubber — General procedures for preparing and conditioning test pieces for physical test methods 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 tensile stress S stress applied so as to extend the test piece NOTE It is calculated as the applied force per unit area of the original cross-section of the test length.
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. Rings and dumb-bells give approximately the same values provided that 1) the elongation of rings is calculated as a percentage of the initial mean circumference and 2) the average value is taken for dumb-bells cut parallel and at right angles to the grain if this is present to a significant degree. Rings might be preferred in automated testing, due to the ease of handling of the test pieces, and in the determination of stress at a given strain.