Accession Number:

ADA027698

Title:

Fracture Stress as Related to Flaw and Fracture Mirror Sizes in Two Polycrystalline Ceramics.

Descriptive Note:

Technical rept. Oct 75-Apr 76,

Corporate Author:

BATTELLE COLUMBUS LABS OHIO

Personal Author(s):

• Bansal,Girraj K.
• Duckworth,Winston H.

Report Date:

1976-05-01

Pagination or Media Count:

42.0

Abstract:

Fractographically observed critical-flaw boundaries in strength-tested specimens of two polycrystalline ceramics were used in calculating critical stress-intensity factors. Each ceramic was found to exhibit a characteristic stress-intensity factor K sub IC having little or no dependence on critical-flaw characteristics. Also, the research indicated that microstructural inhomogenities e.g., large grains or pores which initiate fracturing can be significantly smaller than associated critical flaws. The fractographic interpretations of critical-flaw boundaries were supported by independent determinations of K sub IC using artificially precracked specimens and by analyses both of fracture-mirror sizes and of water-enhanced sub-critical crack growth data. The fracture-mirror analysis further indicated that the parameter, A K sub IC, where A is the fracture-mirror constant, is a dimensionless, material-independent constant that can be evaluated solely from fractographic observations. Author

Descriptors:

• *FRACTURE(MECHANICS)
• *FRACTOGRAPHY
• *CERAMIC MATERIALS
• *BRITTLENESS
• SIZES(DIMENSIONS)
• CRACKING(FRACTURING)
• CRACKS
• GLASS
• CRACK PROPAGATION
• DEFECTS(MATERIALS)
• ALUMINUM OXIDES
• CONSTANTS
• POLYCRYSTALLINE

Subject Categories:

• Ceramics, Refractories and Glass
• Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE