Monitoring of indentation fracture and bending strain in alpha-SiC ceramics utilizing electrical response

Propagation of indentation fracture was firstly monitored on alpha-SiC cera mics through a current drop accompanied by the decrease in current conducti on area. The current decrease ratio before and after indentation during the constant voltage application was proportional to the crack area formed. Ho wever, during the indentation, the current anomalously increased even thoug h the indentation crack propagated. This phenomena is probably due to the p iezoresistance effect which has already reported in SiC single crystal. Whe n bending stress was applied to alpha-SiC ceramics, the current increase ra tio was proportional to the bending strain. A fracture foreseeing system is proposed for alpha-SiC ceramics in which initial crack monitoring without stress application and bending strain monitoring utilizing the piezoresista nce effect are combined. (C) 1999 Kluwer Academic Publishers.