The Brinell Hardness Tester works by creating a controlled indentation on a material's surface and measuring its diameter to determine the material's hardness. Here's a detailed breakdown of the process:

 

l Test Specimen Preparation: The material to be tested is prepared as a flat, smooth surface to ensure an accurate indentation. For uneven or curved surfaces, special adapters might be needed.

l Force Application: The tester applies a predetermined load (weight) through a hardened steel or carbide ball indenter (typically 10 mm in diameter) onto the surface of the test specimen. This load is hydraulically or mechanically controlled and maintained for a specific dwell time (typically 10 to 30 seconds).

l Indentation Formation: Under the applied load, the ball indenter penetrates the test material, creating a spherical indentation. The depth and diameter of this indentation depend on the material's hardness. Harder materials will resist indentation more, resulting in a smaller indentation.

l Load Removal: After the dwell time elapses, the load is gradually removed from the indenter. The indentation remains as a permanent mark on the material's surface.

l Indentation Measurement: A built-in microscope with a calibrated scale is used to precisely measure the diameter of the indentation across two axes. The average of these two measurements is used for further calculations.

l Brinell Hardness Number (BHN) Calculation: Using a formula that factors in the applied load (F) and the measured indentation diameter (D), the Brinell Hardness Number (BHN) is calculated.

Here's the formula: BHN = (2F)/(π * D * (D - (√(D^2 - (d^2)/4)))))

F: Applied load (in kg)

D: Average diameter of the indentation (in mm)

d: Diameter of the ball indenter (typically 10 mm)

Key Points

l The larger the indentation diameter (D), the softer the material (as it yielded more to the indentation).

l A higher BHN value indicates a harder material.

The Brinell Hardness Tester offers a relatively simple and robust method for determining the hardness of various materials, particularly metals and alloys. It's valued for its wide range of applicability and ease of use.

 

You might also be interested in learning more about the Brinell Hardness Tester, such as the differences between it and the Rockwell hardness tester.