In general hardness means the resistance which a body opposes to penetration of a harder penetrating body.
In the industry hardness testing is used for different purposes, e.g. in order to evaluate the hardness of material surfaces, to carry out material confusion testing, or for weld seams, which are needed for specific application.
Testing methods are: The Brinell test of hardness when a ball with a testing load is pressed vertically into the surface, and afterwards the diameter of impression determines the hardness value.
For the Vickers pyramid hardness testing a test load is also pressed vertically into the surface, in this case the impression diagonal indicates the hardness value.
Furthermore, there are the Rockwell hardness test with initial load, the impact hardness test using a ball-type hammer (Poldi-hardness testing device ) and the resilience test of hardness, when a ball falls through a pipe onto the testing body and jumps up again (Equ-Tip).