Hardness is a measure of the hardness of a metal material. At present, the most commonly used method for measuring hardness in production is the indentation hardness method, which presses the surface of the metal material to be tested under a certain load with a certain geometry of the indenter, and determines the hardness value according to the degree of being pressed.

Commonly used methods are Brinell hardness (HB), Rockwell hardness (HRA, HRB, HRC) and Vickers hardness (HV).

The load acting on the machine at a large speed is called the impact load, and the ability of the metal to resist damage under the impact load is called impact toughness.