SLIDING MICROINDENTATION FRACTURE OF BRITTLE MATERIALS - ROLE OF ELASTIC STRESS-FIELDS

An analytical model of the stress field caused by sliding microindenta tion of brittle materials is developed. The complete stress field is t reated as the superposition of applied normal and tangential forces wi th a sliding blister approximation of the localized inelastic deformat ion occurring just underneath the indenter. It is shown that lateral c racking is produced by the sliding blister stress field and that media n cracking is caused by the applied contact forces. The model is combi ned with measurements of the material displacement around an indentati on to show that the relative magnitude of tensile stresses governing l ateral crack and median crack growth varies with the magnitude of the applied load. The model also predicts a range of loads at which the la teral crack will grow only after the indenter is removed from the surf ace. These predictions are consistent with observations of the differe nt regimes of cracking observed under a sliding pyramidal indenter in soda-lime glass and other brittle solids. (C) 1998 Elsevier Science Lt d. All rights reserved.