Analysis of hardness testing indentations

The mentioned heterogeneities were also visible in the mechanical analysis of the nano indentation experiments [63, 75, 77]. We calculated the hardness H and the elastic modulus E from the indentation curves following the model by Oliver and Pharr [80, 81]. In the case of the dense amorphous structure, the mechanical modulus of the sample was homogeneous over the tested area. In contrast, strong scattering of the data was observed in the case of the polycrystalline sample. The latter result reflects the intrinsic structural heterogeneity of the sample. 

Pellicle and tea-immersed pellicle were analyzed using nanoDMA (dynamic mechanical analysis) to see if the tannins had an effect on the viscoelasticity of the pellicle. NanoDMA is a technique used to study and characterize mechanical properties in viscoelastic materials. The method is an extension of nanoindentation testing [58, 59], An analysis of the nanoindentation load-depth curve gives the hardness (H) and reduced elastic modulus (E ), provided the area of contact, A, between the indenter tip and the sample is known [ 13]. By... 

The high elastic strains in polymers affect the pattern of plastic flow in hardness tests. The analysis for metals often assumes an infinite Young s modulus, so the plastically deformed material must flow to free surfaces at the sides of the indenter. For polymers, the yielding process largely occurs directly below the indenter, with elastic expansion of the surrounding region. Figure 8.1 showed the shear band patterns when a strip indenter... 

Non-destructive test (1) A test that yields information about failure under mechanical stress without actually stressing to failure. (2) More broadly, any test to evaluate a property of a material, part, or structure that does not significantly damage the part. Techniques used include ultrasound, magnetic inspection of metals and welds. X-ray inspection, infrared, nuclear magnetic resonance, and sonic analysis. Although an indentation-hardness test leaves a permanent mark, in many tests of parts it is nondestructive. 

Schwartz MM (1992) Handbook of structural ceramics, McGraw-HiU Publishers, USA Guillou MO, HenshaU JL, Hooper RM et al. (1992) Indentation fracture testing and analysis, and its application to zirconia, silicon carbide and silicon nitride ceramics. J of Hard Matls 3 421 34... 

It follows from the above that deviations from parallel variation in abrasiveness and hardness are the outcome of the inaccuracy of measurement, increasing with hardness. Attention should be paid in particular to the microstructure of the material under test in the area of the indentation, and the degree of brittleness should be estimated on morphological analysis... 

It should be noted that these methods work well for inferring the interfacial crack propagation behaviour, but they cannot measure the conditions under which a crack will initiate. Estimates of the interfacial shear stress to initiate debonding can be obtained from indentation tests using an approximate stress analysis in which the coating is assumed very thin, so that stresses are approximately constant through the thickness [34]. In this model [58], the plastic zone below the indentation is modelled as a cylinder, which is replaced conceptually by a hole under an internal pressure (see Fig. 4), p, which is related to the indentation hardness of the material ... 

In recent years there has been much interest in the application of polymer materials at the micro- and nanoscale as microelectronic devices are made smaller and smaller. Constantinides describes an analysis and experiments of materials at the nanoscale. An instrumented pendulum device with a diamond Berkovich indenter was used to indent polymer specimens at a rate of 0.7-1.5 mm/s. The highest impact velocity (1.5 mm/s) corresponded to an impulse energy of 250 nJ. (The Berkovich nanoindenter similar to the Vickers type is normally used for testing the hardness of a material. It has a three-sided pyramid shape. It has also... 

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