Role of Microstructure in Dynamic Fatigue of Glass‐Ceramics after Contact with Spheres

Dynamic fatigue data are reported for fine‐ and coarse‐grained micaceous glass‐ceramics after contact damage with spheres. The strengths of indented specimens are measured at stressing rates from ∼10 −2 to 10 4 MPa·s −1 in water. The strength degradation is substantially faster in the coarse‐grained structure, and is accelerated further by multicycle contact loading. Failures originate from contact sites in all cases but undergo a progressive transition from classical cone cracks to quasi‐plastic microcrack zones with increases in the grain size and the number of contact cycles. The results highlight the particularly deleterious effect of quasi‐plastic damage accumulation on lifetime.