Static indentation tests Vickers

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 second model improves on the first one in the way that static indentation hardness test theory has advanced by introducing plastic deformation into this dynamic system as a parameter. Plastic deformation of the contact area between the particles and the target surface causes radial cracks to propagate outwards from the contact zone and subsurface lateral cracks to move outwards on planes nearly parallel to the surface. Here the parallel with overloaded Vickers static indent tests, which are discussed in detail in... 

Static Indentation Tests, by far the most widely used, the most widely analyzed, and the most generous in the breadth of data they supply. A ball, cone, or pyramid is forced into a surface and the load per unit area of impression is considered the material s hardness. Several types of such tests are well known Brinnel, Vickers, Rockwell, and Knoop. 

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... 

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... 

Figure 9.7 Increased susceptibility to static fatigue due to indentation residual stresses. Vickers-indented (load 5 N) soda-lime glass disks tested under ring-on-ring flexure in water (see also Chapter 8, according to Lawn, 1993).

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