2. Size effects

2.1 Various aspects

The size effect in hardness is associated with the fact that hardness depends on the force applied. This effect is a priori normal in the case of spherical indenters, since material deformation depends on contact size (cf. ). It is also normal to observe such effects when the contact size is comparable to the grain size of the material [29] . On the other hand, it is unexpected in the case of indentations made with pyramid-type conical indenters in materials deemed elastoplastic and homogeneous on the scale of the indentations. Some observations have been physically interpreted and attributed to various phenomena:

• the way in which the...