Contact damage in mica-containing glass-ceramics
- National Institute of Science and Technology, Gaithresburg, MD (United States)
We describe a novel test technique for investigating the susceptibility of glass-ceramics to damage and fatigue. The technique uses a Hertzian indenter in single-cycle or multiple-cycle loading. We show that the nature of damage in local contact stress concentrations changes fundamentally as the base glass is crystallized. In the glassy state, the contact induces a classical, cone fracture. In the crystallized state, discretely distributed subsurface damage is produced, imparting a degree of {open_quotes}quasi-ductility{close_quotes} to the material. Key microstructural parameters associated with this transition in mechanical response are: weak particle matrix interfaces, increased particle size, and enhanced residual thermal mismatch stress. Strength tests indicate that the crystallized material, although weaker in the as-polished state, is less susceptible to catastrophic degradation from repeated contacts. Micromechanisms of damage accumulation in the Hertzian field are explored, and design implications concerning broader mechanical properties, notably fatigue, are discussed.
- OSTI ID:
- 126608
- Report Number(s):
- CONF-950402--
- Country of Publication:
- United States
- Language:
- English
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