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In depth-sensing nanoindentation, the load–depth curve F ( h ) is acquired, from which a single value for hardness H and a second for the indentation modulus E ind are inferred. This is a very poor outcome since F ( h ) is a source of much more information. This paper describes a technique to extract the hardness H ( h ) as a continuous depth-dependent function from the load–depth-curve. This was accomplished by assigning each depth h a corresponding contact depth h C   =   h C ( h ) that can be calculated using an iteration algorithm. The hardness is then simply H ( h )  =   F ( h )/ A C ( h C ( h )). For very simple area functions A C , an analytical solution h C ( h ;   F ) can even be found. Furthermore, the differential hardness H d is introduced as an additional hardness quantity, which is obtained when dividing the load increment Δ F by the resulting increase in contact area Δ A C . It turns out that H and H d are identical quantities for a material of constant hardness only. When the hardness is depth- and, therefore, size-dependent, H d differs from H in a definite way, which depends on the hardness evolution with depth, i.e. on the indentation size effect of the material under investigation. The differential hardness proves particularly useful for inhomogeneous samples and situations where the hardness is time-dependent. [ABSTRACT FROM AUTHOR]

Based on load–depth data, as measured by nanoindentation with a Berkovich tip, stress–strain curves of metal films (Al, Cu and Ti) with thickness of 1 to 4  µm were determined. This so-called inverse analysis was carried out using a neural network approach. The method uses hardness and stiffness data from indentation into the film/substrate composite with a depth range of 10 to 200% of the film thickness, and yields the material parameters describing a nonlinear elastic–plastic stress–strain curve of the Armstrong–Frederick type. It is shown that the method can only be applied if a sufficient difference in film and substrate hardness is present. For all films investigated, a significant dependence of the film strength on its microstructure, as characterized by focused ion beam microscopy, has been found. [ABSTRACT FROM AUTHOR]

There is increasing interest in using sharp cube-corner indenters in nanoindentation experiments to study plastic properties. In combination with finite element methods, it is, for example, possible to extract stress–strain curves from load–displacement curves measured with differently shaped pyramidal indenters. Another example is the fracture toughness of coatings, which can be studied using cracks produced during indentation with cube-corner tips. We have carried out indentation experiments with Berkovich and cube-corner indenters on eight different materials with different mechanical properties. To gain information about the formation of pile-up and cracks, indentation experiments with cube-corner indenter were performed inside a scanning electron microscope (SEM) using a custom-built SEM-microindenter. The results show that reliable hardness and modulus values can be measured using cube-corner indenters. However, the fit range of the unloading curve has a much bigger influence on the results for the cube-corner than for the Berkovich tip. The unloading curves of a cube-corner measurement should, therefore, be carefully inspected to determine the region of smooth curvature, and the unloading fit range chosen warily. Comparison of the modulus results shows that there is no significant difference between cube-corner and Berkovich measurements. Also for hardness, no fundamental difference is observed for most of the investigated materials. Exceptions are materials, such as silicon nitride, cemented carbide or glassy carbon, where a clear difference to the hardness reference value has been observed although the modulus difference is not pronounced. [ABSTRACT FROM AUTHOR]