The present study addresses two cases of brittle ceramic films on metals. With the assistance of AE as a supplementary technique, yield initiation phenomena have been evaluated for W single crystal surfaces under several nm thick native oxide film. An AE sensor coupled to an indenter tip allowed an increasing sensitivity to localized fracture and plasticity events in the vicinity of an indentation contact. A good correlation between AE signals and indentation induced plasticity and fracture has been accomplished for contacts below 100 μN. Second, mechanical behavior of porous nanocrystalline SiC films on Mo substrates was examined. An analysis was based on the P-δ2 approach. With this method, both loading and unloading parts of indentation curves obtained with sharp pyramidal indenters may be represented as P=Kδ2 where P, and δ denote indentation load and displacement respectively. The parameter K includes a material's hardness/modulus ratio and indenter geometry.

The JKR contact mechanics approach is employed to analyze the effects of surface contaminants on adhesive bonding, as well as quantify the level of contamination at which adhesive strength decreases. The contact adhesive forces between two surfaces, one being a soft hemisphere and the other being a hard plate, can readily be determined by applying an external compressive load to join the two surfaces, subsequently applying a tensile load to assess the energy dissipation mechanisms involved in the debonding process. In the present work, we monitor the interactions between a diglycidyl epoxy elastomer and an aluminum oxide substrate in the presence of an organic contaminant. Furthermore, we present a method by which surface contamination can be quantified using a single number, referred to as the adhesion hysteresis parameter, H.

The results of modulus measurements, on carbon black-filled poly(N-vinylpyrrolidone), using dynamic mechanical analysis and nanoindentation were compared. It was shown that beyond the critical pigment volume concentration for this composite system (∼ 25 vol% carbon black), the storage modulus, obtained with dynamic mechanical analysis, decreased with increasing filler concentration. This dropping modulus was due to porosity that developed in the composite films when the critical pigment volume concentration had been exceeded. Elastic modulus obtained with nanoindentation showed the opposite trend, with modulus increasing with additional carbon black loading. An analysis of the method used to calculate modulus based upon indentation data was performed and a mechanism was proposed to explain the disparity between the moduli obtained using these two different methods of measurement.

A combination of depth-sensing indentation and Raman microspectroscopy has been used for the identification of pressure-induced phase transformations in silicon, germanium, boron carbide and partially stabilized zirconia single crystals. Phase transformations during nanoindentation may be revealed through deviations in the shape of the load-displacement curves from that of a perfect elastoplastic material. Such deviations are often more readily identified if the nanoindentation data are presented as average contact pressure vs. contact depth curves, allowing assessment of the corresponding transformation pressures.