Brinell

Brinell refers to the Brinell hardness test, a method for determining the hardness of metals and some composites. It was developed by Johan August Brinell in 1900 and became widely used for industrial material characterization. The test measures resistance to deformation by pressing a hardened spherical indenter into the material surface with a specified force.

In practice, a hardened ball made of steel or carbide is pressed into the material to produce an impression. The ball diameter (commonly 10 mm, but smaller diameters such as 5 mm or 2.5 mm are also used) and the applied load are chosen according to the material’s expected hardness. After indentation, the diameter of the impression is measured, typically with a microscope or projection equipment. The Brinell hardness number is calculated from the indentation diameter, the ball diameter, and the applied load. The standard formula is HB = 2P / (πD(D − sqrt(D^2 − d^2))), where P is the load, D is the ball diameter, and d is the average diagonal of the indentation. Results are often denoted as HB or HBW, the latter indicating a carbide ball and reflecting a difference from steel-ball Brinell testing.

Standards such as ISO 6506 and ASTM E10 specify test procedures, including dwell times, surface preparation, and calculation methods. Brinell hardness values are commonly used for softer metals like steel and cast iron, and for coarse or heterogeneous microstructures where larger indents average the response. Limitations include suitability for relatively soft materials, potential damage on hard or brittle samples, and sensitivity to surface finish.