Contact damage in tough polycrystalline ceramics
- National Institute of Standards and Technology, Gaithersburg, MD (United States)
Results of a research program on the mechanical damage developed in {open_quotes}tough{close_quotes} ceramic materials in Hertzian contacts will be presented. The toughness of these ceramics derives from {open_quotes}grain bridging{close_quotes} across growing cracks. Microstructural characteristics which optimise the bridging include coarse and elongate grains, weak internal interfaces, and high internal stresses. In conventional brittle solids (e.g. glass), Hertzian contacts produce a single macrocrack, the classical Hertzian cone fracture, in the tensile region outside the contact circle. In the tough ceramics, the same microstructural elements responsible for the bridging lead to an altogether new kind of irreversible deformation, in the form of an expanding damage zone in the compression-shear region below the contact. An important manifestation of this deformation is a {open_quotes}quasi-ductility{close_quotes} in the indentation stress-strain response. Micrographic examination of the contact subsurface shows that the damage has the underlying nature of some discrete {open_quotes}shear fault{close_quotes} process, e.g., microtwinning within individual grains, frictional sliding at the weak grain or interphase boundaries. Routes to micromechanical models of these processes will be described. Attention will also be given to implications concerning the prospective design of advanced flaw-tolerant and fatigue- and wear-resistant brittle materials for specific structural applications.
- OSTI ID:
- 175251
- Report Number(s):
- CONF-950686-; TRN: 95:006111-0204
- Resource Relation:
- Conference: Joint applied mechanics and materials summer meeting, Los Angeles, CA (United States), 28-30 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of AMD - MD `95: Summer conference; PB: 520 p.
- Country of Publication:
- United States
- Language:
- English
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