C-Sphere Strength-Size Scaling in a Bearing-Grade Silicon Nitride
- ORNL
- University of Wisconsin, Platteville
A C-sphere specimen geometry was used to determine the failure strength distributions of a commercially available bearing-grade silicon nitride (Si3N4) having ball diameters of 12.7 and 25.4 mm. Strengths for both diameters were determined using the combination of failure load, C sphere geometry, and finite element analysis and fitted using two-parameter Weibull distributions. Effective areas of both diameters were estimated as a function of Weibull modulus and used to explore whether the strength distributions predictably strength-scaled between each size. They did not. That statistical observation suggested that the same flaw type did not limit the strength of both ball diameters indicating a lack of material homogeneity between the two sizes. Optical fractography confirmed that. It showed there were two distinct strength-limiting flaw types in both ball diameters, that one flaw type was always associated with lower strength specimens, and that significantly higher fraction of the 24.5-mm-diameter c-sphere specimens failed from it. Predictable strength-size-scaling would therefore not result as a consequence of this because these flaw types were not homogenously distributed and sampled in both c-sphere geometries.
- Research Organization:
- Oak Ridge National Laboratory (ORNL)
- Sponsoring Organization:
- EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 958894
- Country of Publication:
- United States
- Language:
- English
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