Sliding microindentation fracture of brittle materials: Role of elastic stress fields

An analytical model of the stress field caused by sliding microindentation of brittle materials is developed. The complete stress field is treated as the superposition of applied normal and tangential forces with a sliding blister approximation of the localized inelastic deformation occurring just underneath the indenter. It is shown that lateral cracking is produced by the sliding blister stress field and that median cracking is caused by the applied contact forces. The model is combined with measurements of the material displacement around an indentation to show that the relative magnitude of tensile stresses governing lateral crack and median crack growth varies with the magnitude of the applied load. The model also predicts a range of loads at which the lateral crack will grow only after the indenter is removed from the surface. These predictions are consistent with observations of the different regimes of cracking observed under a sliding pyramidal indenter in soda-lime glass and other brittle solids. (C) 1998 Elsevier Science Ltd. All rights reserved.