Static indentation tests Brinell

Many types of hardness tests have been devised. The most common in use are the static indentation tests, eg, Brinell, Rockwell, and Vickers. Dynamic hardness tests involve the elastic response or rebound of a dropped indenter, eg, Scleroscope (Table 1). The approximate relationships among the various hardness tests are given in Table 2. 

The first of these considers elastic interactions only between the target and the streams of particles which produce ring cracks on the surface of the target. The ring cracks eventually intersect, and material is removed. This model does most closely suit the impingement of low velocity spherical particles. Clearly the Brinell static indentation test is most closely similar because overloaded Brinell spheres produce this type of damage (see 5.2.2). 

For hardness determination, different methods are possible scratching the surface, penetration of an indenter with static or dynamic loads, or rebound as a result of elastic material behavior. The methods with a penetrating indenter are the most important ones. The applied methods are distinguished, e.g., by the shape of the indenter. Brinell hardness is determined by a ball-shaped indenter, while Vickers hardness applies a pyramid-shaped one. After the indenting test with a certain load, the surface area of the indentation is measured which delivers a value for material hardness. Determination of Rockwell hardness uses the depth of the indentation instead of the surface area (Bargel and Schulze 1988). Independent of the method, the so-called surface hardness... 

A further development of static methods of hardness testing was a method devised by Brinell (1900), which consisted of driving a steel ball into the mineral to be tested for hardness under a pressure of 29.4 kN for about 30 seconds. Brinell hardness is defined as the ratio of load to surface of round indentation. The method has found wide use in engineering—for metals it is excellent, but in mineralogy it has proved unsatisfactory because of the high brittleness of most minerals and their non-deformability under the action of the steel ball. The ever wider application of Brinell s method and of a similar method developed by Janko in hardness determination of wood (Krzysik, 1974) should be noted. They are most useful in testing hard wood-base materials, such as compressed wood. 

There are two types of hardness test static tests that involve the formation of a permanent indentation on the surface of the test material and dynamic tests in which a pendulum is allowed to strike the test material from a known distance. Vickers and Brinell tests, two examples of static methods, are the most commonly used methods for determining the hardness of pharmaceutical materials. In the Brinell test, a steel ball of diameter D is pressed on to the surface of the material, and a load F is applied for 30 sec and then removed. The diameter dj of the indentation produced is measured, and the Brinell Hardness Number (BHN) calculated by... 

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