THICKNESS DEPENDENCE OF IMPACT DAMAGE BEHAVIOR IN SILICON-NITRIDE CERAMIC

The thickness dependence of the impact damage behavior of a silicon ni tride ceramic was investigated. For specimens 1.0 mm in thickness, sud den strength degradation occurred over an impact velocity of approxima tely 250 m/s with Hertzian cone crack or bending fracture. Hertzian co ne cracks in 1.0 mm specimens were thought to be enlarged by the scabb ing effect. For 1.5-3.0 mm specimens, strength degradation occurred ab ove a 380 m/s impact velocity with Hertzian cone crack. Therefore, the specimen thickness was related to crack initiation behavior resulting in the strength degradation.