The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science.

History

Proposed by

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

engineer

Johan August Brinell August Brinell (10 October 1849 – 17 November 1925) was a Swedish Metallurgical Engineer Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metalli ...

in 1900, it was the first widely used and standardised hardness test in engineering and

metallurgy Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the sc ...

. The large size of indentation and possible damage to test-piece limits its usefulness. However, it also had the useful feature that the hardness value divided by two gave the approximate UTS in ksi for steels. This feature contributed to its early adoption over competing hardness tests.

Test details

The typical test uses a diameter

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...

ball as an indenter with a 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: :

\operatorname=\frac

where: :BHN = Brinell Hardness Number (kgf/mm) :''P'' = applied load in kilogram-force (kgf) :''D'' = diameter of indenter (mm) :''d'' = diameter of indentation (mm) Brinell hardness is sometimes quoted in megapascals; the Brinell hardness number is multiplied by the acceleration due to gravity, 9.80665 m/s², to convert it to megapascals. The BHN can be converted into the

ultimate tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

(UTS), although the relationship is dependent on the material, and therefore determined empirically. The relationship is based on Meyer's index (n) from Meyer's law. If Meyer's index is less than 2.2 then the ratio of UTS to BHN is 0.36. If Meyer's index is greater than 2.2, then the ratio increases. ''BHN'' is designated by the most commonly used test standards (ASTM E10-14 and ISO 6506–1:2005) as ''HBW'' (''H'' from hardness, ''B'' from brinell and ''W'' from the material of the indenter, tungsten (wolfram) carbide). In former standards HB or HBS were used to refer to measurements made with steel indenters. HBW is calculated in both standards using the SI units as :

\operatorname=0.102 \frac

where: :''F'' = applied load (newtons) :''D'' = diameter of indenter (mm) :''d'' = diameter of indentation (mm)

Common values

When quoting a Brinell hardness number (BHN or more commonly HB), the conditions of the test used to obtain the number must be specified. The standard format for specifying tests can be seen in the example "HBW 10/3000". "HBW" means that a tungsten carbide (from the chemical symbol for tungsten or from the Spanish/Swedish/German name for tungsten, "Wolfram") ball indenter was used, as opposed to "HBS", which means a hardened steel ball. The "10" is the ball diameter in millimeters. The "3000" is the force in kilograms force. The hardness may also be shown as XXX HB YY''D''². The XXX is the force to apply (in kgf) on a material of type YY (5 for aluminum alloys, 10 for copper alloys, 30 for steels). Thus a typical steel hardness could be written: 250 HB 30''D''². It could be a maximum or a minimum.

Standards

* International ( ISO) and European ( CEN) Standard ** ** ** ** * US standard ( ASTM International) **

References

External links