Hardness testing

Ball indentation

The ball indentation hardness is the quotient of the applied load and the surface area of the impression that is present underneath a ball after 30 s at a given load.

The results are required for research and development, quality controls and acceptance or rejection based on specifications. The test method is also suitable for hard rubber.

Kugeldruckhärte Ball indentation
Results of the test method
  • Ball indentation hardness, H [MPa]
  • Force-deformation curve

 

 

 

Rockwell hardness

This test method is used to determine the hardness of a test specimen as a function of the depth of indentation, taking the elastic recovery into consideration.

A steel ball with a defined applied load is pressed onto a test specimen and the load is then released again. Only the plastic deformation is observed. There are various Rockwell hardness scales which differ according to the combination of indenter and applied load.

 

Rockwell hardness scaleIndenter diameter [mm]Applied load [N]
R 12,7 588,4
L 6,35 588,4
M 6,35 980,7
Results of the test method
  • The Rockwell hardness is expressed as a number prefixed by the scale letter (R, L, M).

 

 

 

Shore A and Shore D

These test methods are used to determine the hardness of plastics and elastomers.

Shore hardness is a material parameter for elastomers. The Shore hardness apparatus consists of a spring-loaded indenter whose flexible indentation depth is a measure of the material’s Shore hardness; the hardness is measured on a scale from 0 to 100. A high number means a large hardness.

Shore A is specified for softer elastomer measurements using a needle with a blunted point.

Shore D is specified for harder elastomer measurements using a needle that ends with a 30° point angle and is not blunted.