Finite element analysis of interacting Vickers indentations on brittle materials

A three-dimensional finite element model for interacting Vickers indentations on brittle materials is presented. The induced damage due to double indentations is investigated using an "elastic-plastic-cracking" constitutive model that takes into account "tensile cracking and compressive yielding" behavior in ceramics. The interaction between the induced damage zones and the influence of separation distance between the indentations are assessed by considering simultaneous and sequential Vickers indentations separately. It is shown that for simultaneous double indentations, there exists an optimum separation distance that minimizes the median damage in a ceramic specimen. When the distance between the indenters is small, the combined indenter can be viewed as a single blunt indenter where the extent and severity of damage is comparable to that of a single indentation. The induced damage is found to be proportional to a brittleness parameter that characterizes the propensity for brittle cracking.. When sequential indentations are considered, the damage tends to accumulate in a central region in between the two indentations and the severity of damage is significantly higher. This result is confirmed by conducting experiments on pyrex glass. The implication of these results on grinding of brittle materials, where material removal occurs due to simultaneous interaction of several grits is discussed. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.