Role of Microstructure in Dynamic Fatigue of Glass-Ceramics After Contact with Spheres
J G. Yeo, K -. Lee, Brian R. Lawn
Dynamic fatigue data are reported for fine- and coarse-grain micaceous glass-ceramics after contact damage with spheres. Strengths of indented specimens are measured at stressing rates from 10-2 MPa.s-1 to 104 MPa.s-1 in water. Whereas strength degrades in the usual way with diminishing stressing rate in both materials, the degradation is substantially faster in the coarse-grain structure. The degradation rates are accelerated even further by multi-cycle contact loading. Failures occur from contact sites in all cases, but undergo a progressive transition in origin from classical cone crack to quasiplastic microcrack zone with increase in grain size and number of contact cycles. The results highlight the particularly deleterious effect of quasiplastic damage accumulation on lifetime.