Abstract:
The mechanical and fracture properties of advanced structural ceramics pose difficult problems for the nondestructive assessment of ceramic integrity. The relatively low fracture toughness of these materials means that the critical flaw size is very small, typically 20 microns or less. In addition, the initial mikrostructural state of ceramics is very important to their performance, and changes In that state accompanying in service degradation are also of considerable interest.
However, the microstructural features which dominate the fracture behavior in ceramics occur in a still smaller scale, thus making it difficult to detect such features by conventional linear techniques until failure is imminent. We will describe ongoing work at ORNL designed to insure nondestructive detection of critical flaws in structural caramels and to monitor the the microstructural stab of as-fabricated materials as well as ceramics subjected to in-service conditions. We will discuss the use of radially propagating high-frequency ultrasonic waves for detection of surface and near-surface flaws, the development of aspheric transducer lenses and synched aperture Imaging to improve the signal-to-noise ratio for deeper flaws. and the application of nonlinear acoustics to monitor the interaction of elastic waves with ceramic microstructures.
(Ref. SXVIII-023-97)
Source: NDE of Ceramics '97 May 4-7, Symposium on Nondestructive Evaluation of Ceramics
at the American Ceramic Society 99th Annual Meeting, Cincinnati, Ohio.
Buying the Symposium Proceedings from the American Ceramic Society.
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