Brinellskálán

Brinellskálán is a hardness testing method used to determine the indentation hardness of materials. Developed by Johan August Brinell in 1900, it was one of the first widely used standardized hardness testing methods. The test involves pressing a hardened steel or tungsten carbide ball of a specified diameter into the surface of the material to be tested under a specific load for a predetermined dwell time.

After the load is removed, the diameter of the resulting indentation is measured. The Brinell hardness number (HB) is then calculated by dividing the applied load by the surface area of the indentation. The formula used is HB = 2F / (πD(D - √(D^2 - d^2))), where F is the applied load, D is the diameter of the ball indenter, and d is the diameter of the indentation.

The Brinell test is suitable for materials with a relatively coarse or non-uniform microstructure, such as cast iron and some steels. It is less suitable for very hard materials where the indenter might deform or for very thin materials where the indentation could pass through the sample. The choice of ball diameter and load depends on the material being tested and is often specified by international standards like ISO 6506 or ASTM E10. Common ball diameters are 10 mm, 5 mm, or 2.5 mm, and loads can range from 500 kgf to 3000 kgf. The results are generally expressed as HBW for tungsten carbide balls or HBS for steel balls.