In the Brinell Hardness test, how is the hardness number determined?

In the Brinell Hardness test, the hardness number is determined by measuring the diameter of the indentation left by a hardened steel or carbide ball under specified load conditions. The surface area of this indentation is critical because the hardness value is calculated as the load applied divided by the surface area of the indentation.

This approach to hardness testing helps quantify how resistant a material is to deformation, which is an important property in material selection for engineering applications. The larger the indentation, the softer the material, as it indicates greater deformation under the applied load.

Measuring the depth or the dimensional features of the test piece itself or marking it with a pencil do not contribute to determining hardness in this context. Instead, it is the specific measurement of the impression made on the surface that provides a consistent and reliable hardness value, characteristic of the material being tested.