Brinell test

It was devised in the 1900s by the Swedish engineer Johann August Brinell"). The indenter is a hardened steel sphere, of great hardness, ranging between 1 and 10 mm, to which a pre-established load of between 3000 and 1.25 kp is applied for 15 seconds.

Hardness is calculated by dividing the value of the force applied to the indenter by the surface of the mark it produces in the material.

where HB is the Brinell hardness, and is measured in kp/mm².

The imprint produced by the penetrator has the shape of a spherical cap, whose surface will be:.

From the right triangle it follows that:

and, therefore:

In this way, the surface of the spherical cap will be:.

and the Brindell hardness value will be given by:.

To measure the diameter d of the fingerprint, a microscopic magnifying glass is used. In order not to obtain false values ​​in the measurements, it is necessary that the fingerprint does not present enhancements or recesses on its edges. In order to achieve this, the diameter of the fingerprint must meet the condition.

To ensure that the plastic deformation experienced by the material does not extend to the entire thickness of the piece, the diameter of the ball must be appropriately chosen based on the thickness of the piece being tested.

In order for the marks obtained with balls of different diameters to be similar and the hardness to be comparable, the following must be met.

where K can take different values.

The load application time is usually 15 seconds, although if it is soft materials, the time is longer.

Through the Brinell test and using a proportionality coefficient, the tensile strength can be calculated.

Brinell hardness is expressed:

which means that the material has 250 kp/mm² Brinell hardness, the test was carried out with a 10 mm diameter ball and a load of 500 kp for 30 seconds.

Vickers test

A diamond cut in the shape of a quadrangular pyramid with an angle of 136° between two opposite faces is used as a penetrator. The angle coincides with the Brinell test value for the ratio so that the Brinell and Vickers hardnesses coincide.

Vickers hardness is calculated by dividing the force with which the indenter is pressed by the area of ​​the mark it leaves.

The force is expressed in kp, the surface in mm² and the Vickers hardness unit (HV) in kp/mm².

The imprint on the material will have the shape of a pyramid and its surface will be equal to the four triangles that constitute its faces:

where h is the height of each triangle and a is the length of the base.

The footprint surface will be worth:.

Therefore, the Vickers hardness will be:.

d being the diagonal of the base of the pyramid.

If the load is not applied in the vertical direction, the shape of the footprint will not be square. In these cases the two diagonals are measured and the average value is used.

Loads can vary from 1 to 120 kp, but 30 kp is most common. So that deformations do not occur on the opposite face, the following must be met:

, hence.

where s is the thickness") of the piece and hcosα is the depth of the imprint.

It should be ensured that:

Vickers hardness is expressed as follows:

which means that the material has 315 kp/mm² Vickers hardness and the test was carried out with a load of 30 kp.

Rockwell Essay

Due to its speed of measurement and the small size of the traces it causes, it is the most used test. However, its accuracy is lower. The depth of the footprint is measured.

The steps of the Rockwell test are as follows:.

Hardness testing machines offer the measurement of e in multiples of 0.002 mm, and the maximum value of e is that corresponding to a penetration depth of 0.2 mm.

Contenido

En estos ensayos se mide la resistencia de un material al ser penetrado por una pieza de otro material, denominado penetrador, el cual se empuja con una fuerza controlada y durante un tiempo fijo contra la superficie del material cuya dureza se desea calcular. La velocidad de aplicación de la carga debe ser lenta para que no ejerza influencia en la medida.

El valor de la dureza se obtiene dividiendo la fuerza aplicada al penetrador entre la superficie de la huella que deja en el material.

Brinell test

It was devised in the 1900s by the Swedish engineer Johann August Brinell"). The indenter is a hardened steel sphere, of great hardness, ranging between 1 and 10 mm, to which a pre-established load of between 3000 and 1.25 kp is applied for 15 seconds.

Hardness is calculated by dividing the value of the force applied to the indenter by the surface of the mark it produces in the material.

where HB is the Brinell hardness, and is measured in kp/mm².

The imprint produced by the penetrator has the shape of a spherical cap, whose surface will be:.

From the right triangle it follows that:

and, therefore:

In this way, the surface of the spherical cap will be:.

and the Brindell hardness value will be given by:.

To measure the diameter d of the fingerprint, a microscopic magnifying glass is used. In order not to obtain false values ​​in the measurements, it is necessary that the fingerprint does not present enhancements or recesses on its edges. In order to achieve this, the diameter of the fingerprint must meet the condition.

To ensure that the plastic deformation experienced by the material does not extend to the entire thickness of the piece, the diameter of the ball must be appropriately chosen based on the thickness of the piece being tested.

In order for the marks obtained with balls of different diameters to be similar and the hardness to be comparable, the following must be met.

where K can take different values.

The load application time is usually 15 seconds, although if it is soft materials, the time is longer.

Through the Brinell test and using a proportionality coefficient, the tensile strength can be calculated.

Brinell hardness is expressed:

which means that the material has 250 kp/mm² Brinell hardness, the test was carried out with a 10 mm diameter ball and a load of 500 kp for 30 seconds.

Vickers test

A diamond cut in the shape of a quadrangular pyramid with an angle of 136° between two opposite faces is used as a penetrator. The angle coincides with the Brinell test value for the ratio so that the Brinell and Vickers hardnesses coincide.

Vickers hardness is calculated by dividing the force with which the indenter is pressed by the area of ​​the mark it leaves.

The force is expressed in kp, the surface in mm² and the Vickers hardness unit (HV) in kp/mm².

The imprint on the material will have the shape of a pyramid and its surface will be equal to the four triangles that constitute its faces:

where h is the height of each triangle and a is the length of the base.

The footprint surface will be worth:.

Therefore, the Vickers hardness will be:.

d being the diagonal of the base of the pyramid.

If the load is not applied in the vertical direction, the shape of the footprint will not be square. In these cases the two diagonals are measured and the average value is used.

Loads can vary from 1 to 120 kp, but 30 kp is most common. So that deformations do not occur on the opposite face, the following must be met:

, hence.

where s is the thickness") of the piece and hcosα is the depth of the imprint.

It should be ensured that:

Vickers hardness is expressed as follows:

which means that the material has 315 kp/mm² Vickers hardness and the test was carried out with a load of 30 kp.

Rockwell Essay

Due to its speed of measurement and the small size of the traces it causes, it is the most used test. However, its accuracy is lower. The depth of the footprint is measured.

The steps of the Rockwell test are as follows:.

Hardness testing machines offer the measurement of e in multiples of 0.002 mm, and the maximum value of e is that corresponding to a penetration depth of 0.2 mm.