Hardness test methods
BrinellIRHD normal, IRHD low, IRHD micro, IRHD very low (DIN ISO 48)
Principle:
The hardness test is based on the measurement of the difference in the indentation depths of a hardened steel ball in the elastomer which arises for a small preliminary test force and a large total test force.
The ball indentation hardness IRHD (International Rubber Hardness Degree) is a numerical value taken from a table, which is depends on the respective indentation depth under the acting test force.
Forces and dimensions of the test device
| Hardness scale | Diameter | Preliminary force | Additional force | Total force | Force acting from the pressure foot onto the sample surface |
| mm | N | N | N | N | |
| IRHD N | Ball: 2,50 Foot: 20 Hole: 6 | 0,30 | 5,40 | 5,70 | 8,3 |
| IRHD L | Ball: 5 Foot: 22 Hole: 10 | 0,30 | 5,40 | 5,70 | 8,3 |
| mm | mN | mN | mN | mN | |
| IRHD M | Ball: 0,395 Foot: 3,35 Hole: 1 | 8,3 | 145 | 153,3 | 235 |
| VLRH | Ball: 2,5 Foot: 6,0 Hole: 3,0 | 8,3 | 91,7 | 100,0 | 235 |
Fields of application:
| Hardness scale | Fields of application |
| IRHD N | Soft to medium-hard rubber, very soft thermoplast |
| IRHD L | Soft to medium-hard rubber, very soft thermoplast |
| IRHD M | Soft to medium-hard rubber, very soft plastics, plane and lightly curved samples, small semi-finished parts or finished parts or rubber coatings, also relatively thin samples |
| VLRH | Silicones |