ASTM D1415 & ISO 48-2 IRHD Hardness
ASTM D1415 and ISO 48-2 describe four methods for testing specimens of vulcanized or thermoplastic elastomers on flat surfaces. Hardness is expressed in International Rubber Hardness Degrees (IRHD). The methods differ mainly in the diameter of the ball indenter and the applied indentation force, which are selected according to the application.
Objective & Applications Specimens Running a test Requirements Test equipment Request a consultation
ASTM D1415 & ISO 48-2 objective and applications
The international hardness test according to ASTM D1415 and ISO 48-2 measures how deeply a solid ball penetrates a rubber specimen under certain conditions. The measured indentation depth is converted into IRHD, where 0 stands for extremely soft material and 100 for extremely hard material. This is important to ensure the quality and consistency of rubber materials for industrial applications and is used in the areas of quality assurance, and incoming and outgoing goods inspection by manufacturers and processors in the plastics and rubber industries.
ASTM D1415 & ISO 48-2 Specimens and dimensions
In order to achieve comparable results, the tests must be carried out on specimens of the same thickness with smooth, even, and parallel upper and lower surfaces. Up to three specimens may be placed on top of each other to achieve the required thickness. The thickness of the specimens depends on the hardness measurement method used.
- Type S1 and S2 and H specimens must be between 8 and 10 mm thick. Non-standardized specimens can be either thicker or thinner, but in no case less than 2 mm thick.
- The specimens for the type M microhardness test must have a thickness of 2 ± 0.5 mm. Non-standardized specimens can be either thicker or thinner, but in no case less than 1 mm thick.
- Type L specimens must have a thickness of 10 to 15 mm. Standardized specimens can be either thicker or thinner, but in no case less than 2 mm. Non-standard specimens may be either thicker or thinner, but never less than 6 mm.
ASTM D1415 & ISO 48-2 Running a test
The ASTM D1415 & ISO 48-2 test should preferably be performed at a temperature of 23 ± 2 °C (73.4 ± 3.6 °F). Immediately before the test, the specimens must be kept at the test temperature for at least 3 hours. The top and bottom of the specimen is first lightly dusted with talcum powder. The specimen is then placed on a stable, horizontal surface. The foot is lowered until it rests on the surface of the specimen. Now the plunger is pressed with the minor force on the indenting ball, vertically onto the specimen for 5 seconds. The movement of the plunger caused by the application of the major force is recorded for 30 seconds.
Three or five measurements are taken at different points on the specimen and the median of these measurements is taken, rounded to the nearest displayed unit of IRHD (whole numbers for analog devices and 0.1 units for digital devices).
ASTM D1415 & ISO 48-2 Requirements and test equipment
ZwickRoell IRHD measuring instruments are particularly suitable for testing to ASTM D1415 and ISO 48-2. The IRHD micro compact hardness tester consists of a basic housing with integrated electronics and display, a height-adjustable support table for the test specimens and a column with integrated IRHD micro measuring device and can be used to test O-rings, seals, molded parts and hoses.
The ZwickRoell combi test measuring instrument, a microcomputer-controlled hardness tester with very high measuring accuracy in several IRHD (also IRHD-ss supersoft) and Shore measuring ranges, offers fast and highly accurate measurement without operator influence thanks to automatic test sequences.
Frequently asked questions about IRHD hardness testing
IRHD hardness is calculated by measuring how deep a ball penetrates a rubber specimen under two different forces: first with a minor force and then with a major force. The difference in indentation depth is measured and converted into the IRHD (International Rubber Hardness Degree) hardness value using a specified table or diagram.