ISO 48:2010 pdf free download.Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRHD and 100 IRHD).
ISO 48:2010 specifies four methods for the determination of the hardness of vulcanized or thermoplastic rubbers on flat surfaces (standard-hardness methods) and four methods for the determination of the apparent hardness of curved surfaces (apparent-hardness methods). The hardness is expressed in international rubber hardness degrees (IRHD). The methods cover the hardness range from 10 IRHD to 100 IRHD.
The hardness test specified in this International Standard is intended to provide a rapid measurement of rubber stiffness, unlike hardness tests on other materials which measure resistance to permanent deformation.
Hardness is measured from the depth of indentation of a spherical indentor, under a specified force, into a rubber test piece. An empirical relationship between depth of indentation and Youngs modulus for a perfectly elastic isotropic material has been used to derive a hardness scale which can conveniently be used for most rubbers.
When it is required to determine the value of Youngs modulus itself, it is expected that an appropriate test method be used, for example that described in ISO 7743.
The guide to hardness testing, ISO 18517, can also be a useful reference.
2 Normative references
ISO 18898, Rubber-Calibration and verification of hardness testers;
ISO 23529, Rubber -General procedures for preparing and conditioning test pieces for physical test methods.
The hardness test consists in measuring the difference between the depths of indentation of a ball into the rubber under a small contact force and a large(indenting ) force. From this difference, multiplied when usin le microtest by the scale factor 6, the hardness in IRHD is obtained from Tables 3 to 5 or from graphs based on these tables or from a scale, reading directly in RHD, calculated from the tables and fitted to the indentation-measuring instrument. These tables and curves are derived from the empirical relationship between indentation depth and hardness given in Annex A.