Indentation fracture mechanics

The development of indentation fracture mechanics has also allowed fracture toughness to be determined using indentation cracks. Indeed, the ease with which these cracks can be introduced and the simple specimen preparation involved has popularized this approach. Moreover, it has allowed crack behavior to be studied for cracks in a size range that is close to that found in practice. There are two main approaches for determining fracture toughness from indentation cracks. In the first approach, the size of the radial cracks that emanate from the hardness impression are measured. It is recognized that the parameter x depends on the elastic properties of the indented material. It has been proposed that x=P E H), where )8 is a constant that depends only on the indenter geometry and H is hardness. Equation (8.64) can, therefore, be written as... 

Ceramics can often be damaged under low contact loads and, thus, it is important to understand these damage mechanisms. These processes not only give rise to strength degradation but are linked to wear and erosion. Indentation fracture mechanics has been found to be a very useful approach in understanding these contact-damage processes (see Section 8.8). 

Lac Each, R., Gyurova, L. A.,Grellmann, W. Application of indentation fracture mechanics approach for determination of fracture toughness of brittle polymer systems. Polym. Test. 26 (2007) 51-59. 08Pin Pinter, G. Slow crack growth in PE-HD under static and cyclic loads. Habilitation thesis, Montanuniversitat Leoben, 2008. 

Lac Lach, R., Kim, G. M., Michler, G. H., GreUmann, W., Albrecht, K. Indentation fracture mechanics for toughness assessment of PMMA/Si02 nanocomposites. Macromat. Mater. Eng. 

The indentation fracture mechanics approach likens abrasive-workpiece interactions for grinding of ceramics to small-scale indentation events. The deformation and fracture patterns observed for normal contact with a Vickers pyramidal indentor under an applied load P are illustrated in Figure 3.1. A zone of plastic deformation is foimd directly imder the indentor. Two principal crack systems emanate from the plastic zone med-ian/radial and lateral cracks. Median/radial cracks are usually associated with strength degradation and lateral cracks with material removal. 

Most past research on grinding mechanisms for ceramics has followed either the indentation fracture mechanics" approach or machining" approach. The indentation fracture mechanics approach would seem to offer the possibility of describing both the material removal process and its influence on strength degradation in terms of the force or depth of cut at an... 

Marshall, D.B. and Lawn, B.R., 1979, Residual stress effects in sharp contact cracking part 1 indentation fracture mechanics, /. Mater. Sci., Vol. 14,... 

Indentation-fracture mechanics approach, which models abrasive-workpiece interactions by the idealized flaw system and deformation produced by an indenter. 

Thouless et al. derived a model based on buckling of an edge flake that predicted n=3. An indentation fracture mechanics model by Chai and Lawn for edge chip resistance is also consistent with the power law eq, 2, but only for the case of /r = 1.5. Although some of our data matched the power law with rr = 1.5, much of it did not. Exponents ranged from as small as 1 to as large as 2. Problems remain with the interpretation of the exponent n and the constant A. Is /r a fundamental material parameter indicative of a material s chipping behavior Can it be related to other material properties What are the units of A ... 

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