Influence of grinding direction on fracture strength of silicon nitride

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:175236

Strakna, T J; Jahanmir, S ^[1]; Allor, R L ^[2]; Kumar, K V ^[3]

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1. National Institute of Standards and Technology, Gaithersburg, MD (United States)
2. Ford Motor Company, Dearborn, MI (United States)
3. General Electric Superabrasives, Worthington, OH (United States)

It is generally found that grinding transverse to the tensile stress direction in flexure bars subjected to four-point bending results in a lower strength compared to grinding in the longitudinal direction. In the present study, standard flexure specimens made from a reaction-bonded and a sintered reaction-bonded silicon nitride (RBSN and SRBSN) were surface ground under three different conditions in both longitudinal and transverse directions to assess the effect of grinding direction on strength. Four-point flexure tests were performed on the specimens and Weibull parameters were calculated. The results showed that while the strength was not affected by the grinding condition when grinding was performed in the longitudinal direction, the strength of the samples ground in the transverse direction was reduced as the material removal rate was increased by a factor of 30. This result was confirmed by fractography, which showed that almost all the fracture initiation sites in the longitudinally ground samples were associated with near-surface microstructural features, whereas in the transverse ground samples fracture initiated from damage introduced by grinding. The strength reduction by grinding in the transverse direction was found to be material dependent, and was larger for SRBSN than for RBSN.

• OSTI ID: 175236
• Report Number(s): CONF-950686--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BENDING
CORRELATIONS
FLEXURAL STRENGTH
FRACTOGRAPHY
FRACTURE PROPERTIES
GRINDING
SILICON NITRIDES