Influence of grinding direction of fracture strength of silicon nitride

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Journal of Engineering Materials and Technology

DOI:https://doi.org/10.1115/1.2806815· OSTI ID:413232

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

---

1. National Inst. of Standards and Technology, Gaithersburg, MD (United States)
2. Ford Motor Co., 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.

• Sponsoring Organization: National Inst. of Standards and Technology, Gaithersburg, MD (United States)
• OSTI ID: 413232
• Journal Information: Journal of Engineering Materials and Technology, Journal Name: Journal of Engineering Materials and Technology Journal Issue: 3 Vol. 118; ISSN 0094-4289; ISSN JEMTA8
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CRACKS
DAMAGE
DEFECTS
EXPERIMENTAL DATA
FLEXURAL STRENGTH
FRACTOGRAPHY
FRACTURE PROPERTIES
GRINDING
IRON OXIDES
MECHANICAL PROPERTIES
OPTICAL MICROSCOPY
PARAMETRIC ANALYSIS
PHYSICAL PROPERTIES
ROUGHNESS
SAMPLE PREPARATION
SCANNING ELECTRON MICROSCOPY
SILICON NITRIDES
SURFACES
YTTRIUM OXIDES