Analysis of penetration curves produced by sharp indentations on ceramic materials

Indentation load-penetration curves from sharp indentations (Vickers indentation and nanoindentation) on several ceramic materials were analysed using newly developed three-dimensional finite-element (FEM) numerical models, based on elastic and elastoplastic calculations. The results have led to a general methodology to analyse the penetration curves obtained from both Vickers indentations and nanoindentations on bulk materials. It is found that it is necessary to proceed with separate analyses for the loading and unloading curves, although the analyses are related. Through a detailed analysis of the load-depth curves, information related to various compressive mechanical properties is obtained from different portions of the load-penetration curves. From the loading curve, the hardness, yielding stress, strain hardening, surface displacement and plastic zone size are obtained, whereas the elastic modulus is obtained from the unloading curve. Experimentally reported indentation load-penetration curves both from Vickers indentations and nanoindentations for different glasses and ceramics are analysed in detailed using the method developed here. Various mechanical properties are obtained from such curves and show good agreement with the literature values. The effects of cracking on these properties are also discussed in association with the indentation-induced damage.