Rate-Dependent Indentation Response of Structural Ceramics

摘要

Static and dynamic (high-rate) indentation hardness values are determined for ZrO_2, SiC, and Si_3N_4 ceramics. While the static hardness is determined using a conventional Vickers tester, the dynamic hardness is determined using a custom-designed tester that can produce a single indent within a 100-μs duration. The results indicated that the dynamic hardness is 7%-10% greater than the static hardness, depending on the type of ceramic material. Indentation-induced crack length is also appreciably smaller under dynamic indentation compared with static indentation. However, when the influence of increased hardness (I.e., reduced indentation size) under dynamic indentation is factored into the crack length measurements, the difference in crack length between static and dynamic indents disappears for SiC and Si_3N_4. In the ZrO_2 ceramic, the difference in crack lengths continues to persist, indicating that ductile behavior (transformation toughening) may be a factor for rate-dependent fracture characteristics in ceramics in this strain rate regime.