Knoop

KNOOP

BACKGROUND INFORMATION KNOOP HARDNESS TESTING (DIN EN ISO 4545) In 1939, Knoop, Emerson and Peters developed the Knoop hardness test method in order to enable a more reliable hardness test in thin layers. Basically, it is very similar to the Vickers hardness test. Here, a rhombic diamond pyramid with a longitudinal edge angle of 172.3° and a transverse edge angle of 130° is used as the indenter. This indenter is in turn pressed vertically into a workpiece surface with a specific test force. After unloading, the resulting indentation is measured, and only the long diagonal d1. The Knoop hardness is then calculated as the quotient of the test force and the projection area of the in-dentation. The Knoop method is only used in the small force (up to 10 N) and micro hardness range.
1. Indentation of the diamond pyramid with test force F into the test specimen	2. Measurement of the long diagonal d1 of the indentation
KNOOP HARDNESS TESTING RESULTS According to DIN EN ISO 6508-1 the result of a Knoop hardness test is indicated as follows: 700 HK 0.2 / 20 ⇒ Hardness value as per Knoop 700 HK 0.2 / 20 ⇒ Abbreviation for Knoop hardness 700 HK 0.2 / 20 ⇒ Test force specification: Test force [N] = 9.807 * test force specification 700 HK 0.2 / 20 ⇒ Application time of the test force (omitted if it is between 1-15 s)