The Brinell scale characterizes the

indentation hardness Indentation hardness tests are used in mechanical engineering to determine the hardness of a material to deformation. Several such tests exist, wherein the examined material is indented until an impression is formed; these tests can be performed on ...

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 Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the limit ...

Johan August Brinell August Brinell (10 October 1849 – 17 November 1925) was a Swedish Metallurgical Engineer. Brinell is noted as the creator of a method for quantifying the surface hardness of materials, now known as the Brinell hardness test. His name is also ...

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

engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...

and metallurgy. 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 Olajide Olayinka Williams "JJ" Olatunji (born 19 June 1993), known professionally as KSI, is an English YouTuber and rapper. He is a co-founder and member of the British YouTube group known as the Sidemen. He is the CEO of Misfits Boxing and ...

for steels. This feature contributed to its early adoption over competing hardness tests.

Test details

The typical test uses a

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

steel ball as an indenter with a force. For softer materials, a smaller force is used; for harder materials, a

tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...

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 Meyer's law is an empirical relation between the size of a hardness test indentation and the load required to leave the indentation.. The formula was devised by Eugene Meyer of the Materials Testing Laboratory at the Imperial School of Technology, ...

. 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 ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

) and European ( CEN) Standard ** ** ** ** * US standard (

ASTM International ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, ...

) **

References

External links