Brinell Hardness Testing Machine Wilson® Model J
J.A. Brinell proposed the first widely accepted and standardized hardness test in 1900. A steel ball is pressed into the surface of the specimen by a known load to plastically deform the material. The fundamental concept is that the diameter of the indentation in a harder material has a smaller diameter. The Brinell hardness number (BHN or HB) is inversely proportional to the surface area of the indentation.
The Wilson® Model "J" Brinell Hardness tester is a hand operated mechanical device. A dash pot system restricts the rate of application of the load to avoid dynamic effects. A 10mm diameter hardened steel ball is pressed into the specimen. The load is adjustable. Applied loads from 500kg to 3,000kg are generated with different installed masses. Smaller loads are used for soft materials and larger loads for harder materials. For very hard materials a 10mm diameter tungsten-carbide ball is installed.
The specimen is placed on the anvil and raised to contact the ball by rotating the handwheel at the bottom of the anvil column. The handle on the right side is pushed backward to contact the rear stop. The dashpot system restricts the rate of movement. The load is held for 15 seconds to ensure that the plastic zone forms completely. The handle is pulled back and the anvil is lowered.
The Brinell hardness number (HB) is the load divided by the surface area of the indentation. The diameter of the impression is measured with a microscope with a superimposed scale. The Brinell Hardness Number HB is computed from the equation:
where
- P is the applied load of 3,000, 1,500, or 500kg.
- D is the diameter of the ball in mm. (10mm)
- d is the mean diameter of the indentation in mm.
- The units of HB are kg/mm^2. However, the results are usually reported with no units.