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The hardness number is based on the applied force divided by the surface area of the indent itself, giving hardness units in kgf/mm 2. Microindentation hardness testing can be done using Vickers as well as Knoop indenters. For the Vickers test, both the diagonals are measured and the average value is used to compute the Vickers pyramid number.
The typical test uses a 10 mm (0.39 in) diameter steel ball as an indenter with a 3,000 kgf (29.42 kN; 6,614 lbf) force. For softer materials, a smaller force is used; for harder materials, a tungsten carbide ball is substituted for the steel ball. The indentation is measured and hardness calculated as:
A Rockwell hardness tester. The Rockwell hardness test is a hardness test based on indentation hardness of a material. The Rockwell test measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load). [1]
Brinelling / ˈ b r ɪ n ə l ɪ ŋ / is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface. Brinelling is permanent plastic ...
For the situation where the asperities on the two surfaces have a Gaussian height distribution and the peaks can be assumed to be spherical, [31] the average contact pressure is sufficient to cause yield when = where is the uniaxial yield stress and is the indentation hardness. [1]
The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The hardness number can be converted into units of pascals, but should not be confused with pressure, which uses the same units. The hardness number is determined by the load over the surface area of the indentation and not the ...
BHN = load in kilograms divided by the spherical area of the indentation in square millimetres (refer to Brinell scale for method of calculation) It is a rapid, non-destructive (except at the surface being tested) means of determining the hardness of metals. This area is a function of the ball diameter and the depth of the indentation.
The hardness is given by the equation above, relating the maximum load to the indentation area. The area can be measured after the indentation by in-situ atomic force microscopy, or by 'after-the event' optical (or electron) microscopy. An example indentation image, from which the area may be determined, is shown at right.