Brinelltester

The Brinell hardness tester is a device used to measure the hardness of metals by pressing a hard spherical indenter into a material surface under a controlled load. The size of the resulting indentation is used to determine the Brinell hardness number (BHN). The method was developed by Johan August Brinell in 1900 and remains in use for certain metals and applications.

Principle and calculation: A hardened steel or carbide ball of a specified diameter D (commonly 1, 2.5, 5, or 10 mm) is forced into the material with a known load F (typically 500 to 3000 kgf). The diameter d of the indentation is measured with optical means. The Brinell hardness number is defined by BHN = 2F / (π D (D - sqrt(D^2 - d^2))). In practice, F is in kgf and D and d are in millimeters, and BHN is reported in HB.

Indenter sizes and test conditions: Ball diameters and loads are chosen according to the material and expected hardness. Larger balls and higher loads are used for harder metals, smaller for softer ones. The method can accommodate rough surfaces and larger, coarse-grained structures, which can influence measurement accuracy.

Procedure: The specimen surface should be clean and reasonably flat. The indenter is aligned with the surface, and the load is applied gradually and held for a dwell time before release. The indentation is measured with a microscope or micrometer, and BHN is computed from the measurements.

Applications and standards: Brinell testing is common in metal production, casting, and quality control, especially for softer metals and larger components. It is standardized by ISO 6506 and ASTM E10, among others. It is often considered alongside Rockwell and Vickers tests, offering advantages in certain surface and material conditions but with limitations for very hard materials or very small samples.