Abstract
IN this study, critical condition for ring cracking of turbine-grade Si_3N_4 ceramic was examined through the Sm_2Co_<17> particle impact (dynamic loading) test and the quasi-static indentation (static loading) test. Moreover, some indentation tests using split specimen (or BIT) were carried out. Regarding the stress for the ring cracking, hydrodynamic pressure assumption (pcv) gave plausible value to that by the quasi-static indentation test within the present combination of materials. Indentation in the split specimen brought Hertzian cracks. In the continuous specimen, however, no cracks appeared at the same load.
