the measurement principle of brinell hardness is to use a certain size of test force f (n) (the unit of force is usually kilogram force kgf, note: 1kgf=9.8n, kgf means one kilogram of force), and the diameter a quenched steel ball or cemented carbide ball of d (mm) is pressed into the surface of the metal to be tested, and the test force is removed after holding for the specified time. use a reading microscope to measure the average diameter of the indentation d. (mm), and then calculate the brinell hardness hb value according to the formula, or find out the hb value from the prepared brinell hardness table according to d.

formula:

BHN = (2*P) / [ (pi*D)(D - sqrt(D²-d²)) ]