# Vickers hardness number

## Description

The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials.The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The basic principle, as with all common measures of hardness, is to observe the questioned material’s ability to resist plastic deformation from a standard source. The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH)

The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not pressure. Substituing the area the HV can be expressed in function of the force and the the average length of the diagonal left by the indenter.

The corresponding units of HV are kilograms-force per square millimeter (kgf/mm²). To convert the Vickers hardness number to SI units the hardness number in kilograms-force per square millimeter (kgf/mm²) has to be multiplied with the standard gravity (9.806 65) to get the hardness in MPa (N/mm²) and furthermore divided by 1000 to get the hardness in GPa.

Related formulas## Variables

HV | hardness number (kgf/mm^{2}) |

F | force applied to the diamond (kgf) |

θ | angle of the indenter (136 degrees) (rad) |

d | average length of the diagonal (mm) |