Hardness is the mechanical property of the material which helps him in resisting the plastic deformation of the material. Plastics deformation can be form the starching, compression or due to indentation of any object in the work piece. Brinell hardness test is performed to find the hardness typically called the Brinell hardness.
- Brinell hardness test in perform in such a way that first of all a work piece made of desire material is obtain and is fixed on the plate form of the brinell hardness testing machine.
- Then a small ball usually of 10 mm diameter, made of tungsten carbide is used to apply the load of about 3000 kg on the work piece. Load is applied for certain duration and then removed.
- Due to such high load the ball penetrate into the outer surface of the work piece and upon removal make cavity at that position.
- Diameter of the cavity is measured from at least two positions and these positions should be at right angle of each other.
- The diameter measured is then compared with the standard table provided with Brinell hardness machine form where the diameter reading is converted into the Brinell hardness number of the material.
- Cavity diameter measured from the Brinell hardness machine is converted into the Brinell hardness number by the help of following formula
HB= 2F/(π×D×(D-√(D-d) ) )
F is the load applied
D is diameter of the ball used for indentation
d is the diameter of the impression produce by the ball on the work piece
HB is the Brinell hardness number of the material
Indentation measurement is the biggest error source in the Brinell hardness test because the measuring method is manual due to which the human error can cause problem. Due to the inexperience operator taking the reading the results of the experiment will different under the perfect condition but the non-perfect condition will bring more changes in the result.
Over the years there two technologies developed to overcome the errors of the Brinell hardness test one is the automatic optimal Brinell scope and other is the Brinell units. First one make use of computer and images analysis to measure the Brinell hardness and second one make use of the ASTM E103 standard units to measure the Brinell hardness. The surface condition of the work piece can really affect the result of the experiment so that’s why the surface of the work piece is prepared by grinding.
Brinell hardness number which is obtain from the Brinell hardness test is used to determine the hardness of any material or in other works the ability of the material to stop any object from penetrating into it. It can be said in the other words like that, Brinell hardness number of any material show its ability to maintain its shape or the ability of the material to resist the change in its shape.
Brinell hardness number is used to select the material for the application where the outer shape of the object or product is very important like in aerospace application. Brinell hardness number can also be used for the selection of the material for the application where the object need to be hard enough to resist the penetration of any object in it like military tanks and built proof vehicles.