MICRO-INDENTATION TESTS WITH POINTED INDENTERS

Mechanical properties of surface layers, thin films or small volumes o f material can be studied using ultra-microindentation devices, whereb y the indenter displacement is measured continuously during loading an d unloading. This approach enables hardness, elastic modulus, yield st rength and the energy spent on loading or unloading to be determined. Also other material characteristics can be defined, such as the elasti city index and the indentation work per unit volume of the permanent i mpression. Loading and unloading curves may be described by simple pow er-law functions, which are important for the evaluation of data, but can also be utilised for modelling of contact loading. Pointed indente rs (Berkovich, Vickers) deform under conditions of constant strain, wh ich is advantageous when material properties in a larger range of dept hs are studied, particularly if these properties change with depth. In the paper, the determination and use of the above quantities is illus trated for tests done with Berkovich indenter on steel and glass.