ANALYSIS OF BRIDGE-INDENTATION PRECRACKING

In the bridge indentation method, developed by earlier researchers to produce precracks, the precracks in brittle bars can be conveniently p roduced by the unstable pop-in of a Vickers indentation starter crack using bridge-type loading. Because of the numerous test variables invo lved, optimization and control of the precrack length can be difficult . Based on experimental data, it was found that relative stiffness, pl aten contact-surface friction and loading geometry can significantly a ffect the precracking behaviour. The various effects were analysed usi ng a parametric finite-element analysis. The predictions were compared with experimental data and the behaviour was rationalized using simpl e approximations for the stress distributions.