IRHD Hardness - ASTM D1415
IRHD: International Rubber Hardness Degrees
A measure of the indentation resistance of elastomeric or rubber materials based on the depth of penetration of a ball indentor.
An initial contact force is applied to an indentor and the penetration is set to zero. The force is increased to a specified total load and the depth of penetration is measured. The IRHD value is related to the depth of indentor penetration.
For highly elastic materials, IRHD and Shore A are comparable.
An IRHD value of 0 represents a material with an Young's Modulus of zero and an IRHD value of 100 represents a material with an infinite Young's Modulus.
The relationship between the depth of penetration (hardness) and the IRHD number is based on:
F is the indentation force in Newtons,
E is the Young's Modulus in MPa,
r is the indentor ball radius in mm, and
D is the depth of penetration in mm.
|Test||Ball Diameter (mm)||Contact Force (N)||Total Force (N)||Thickness (mm)||IRHD Range|
|N (Normal)||2.5||0.3||5.7||4||30 to 95|
|H (High-Hardness)||1.0||0.3||5.7||4||85 to 100|
|L (Low-Hardness)||5.0||0.3||5.7||6||10 to 35|
|M (Micro)||0.395||0.0083||0.153||4||30 to 95|