TABLE OF CONTENTS Tests known as "hardness tests" measure the average contact pressure of materials when an indenter (conical, pyramidal or spherical) is pressed into a flat surface. After the withdrawal of the indenter, hardness is calculated by measuring the dimension of the indentation made by the indenter, or during the test, with the help of a penetration curve, which relates the depth of penetration to the applied load.
When hardness is measured on a ductile material under the conditions defined by the standards [MAT 94a, 94b, 98], it can be regarded as an intrinsic material parameter. Although the result obtained is pressure, it is expressed without dimension since the measured pressure depends on the geometry of the indenter. Thus, the value of hardness is a number (average contact pressure expressed in kgf/mm 2) followed by H (for hardness) and an index which indicates the type of indenter used ( V for Vickers or B for Brinell, for example).
The main advantage of this test is that it can be performed on very small-sized samples without any preparation except polishing of the surface. This allows us to test the success of a surface treatment over a few hundred micrometers in depth, or the quality of surface coating, or the size of the zone affected by the welding of two sheets, etc. It is preferentially used when the removal of conventional tensile test pieces is difficult. Micro-hardness and nano-hardness tests were developed in order to test smaller and...
